You searched for subject:(Geophysics).
Showing records 1 – 30 of
3094 total matches.
◁ [1] [2] [3] [4] [5] … [104] ▶
1.
Dhar, Mahesh Singh.
Station delays, their standard deviations, and event relocations in the Reno-area basin from a dense USArray flexible array deployment during the 2008 west Reno earthquake swarm.
Degree: 2010, University of Nevada, Reno
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=1480794 
► The seismic hazard of a sedimentary basin is high. The basin depth and its geometry control the amplification of ground motion. So from the…
(more)
▼ The seismic hazard of a sedimentary basin is high. The basin depth and its geometry control the amplification of ground motion. So from the point of earthquake hazard, it is important to know the basin geometry and its depth for the hazard evaluation of an area. Knowing the basin geometry and depth and velocity of sediments will enhance our understanding of ground amplification to improve seismic hazard evaluations. In this context, to evaluate the seismic hazard of the Reno Basin, the Nevada Seismological Laboratory (NSL) conducted a citizen volunteer Reno Basin multiple instrument temporary deployment using USArray Flexible Array single-channel RefTek RT-125A (Texan) recorders. Stations were deployed at 106 locations in the Reno Basin during the May-July 2008 period of the 2008 west urban Reno Mogul earthquake swarm. This was a very dense deployment as the basin only occupies about 150 square kilometers. The Flexible Array deployment supplemented recordings from 46 NSL/ANSS regional network stations, Reno area strong-motion, and 12 IRIS RAMP stations. This allowed relocation of 97 events in the West Reno/Mogul sequence during May-July 2008, using phase arrivals on all network and volunteer Texan stations. Hypoinverse runs showed no less location error with added Texans, but visually, the events are drawn into tighter clusters. An average station delay map, a mode-of-station-delay map, and a map of the standard deviations of the average station delays confirm that the western part of the basin is thickest. Negative delays and high standard deviations in delay times in the Verdi Basin confirmed the basin to be narrow and complex.
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Dhar, M. S. (2010). Station delays, their standard deviations, and event relocations in the Reno-area basin from a dense USArray flexible array deployment during the 2008 west Reno earthquake swarm. (Thesis). University of Nevada, Reno. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=1480794
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Dhar, Mahesh Singh. “Station delays, their standard deviations, and event relocations in the Reno-area basin from a dense USArray flexible array deployment during the 2008 west Reno earthquake swarm.” 2010. Thesis, University of Nevada, Reno. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=1480794.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Dhar, Mahesh Singh. “Station delays, their standard deviations, and event relocations in the Reno-area basin from a dense USArray flexible array deployment during the 2008 west Reno earthquake swarm.” 2010. Web. 23 Apr 2018.
Vancouver:
Dhar MS. Station delays, their standard deviations, and event relocations in the Reno-area basin from a dense USArray flexible array deployment during the 2008 west Reno earthquake swarm. [Internet] [Thesis]. University of Nevada, Reno; 2010. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=1480794.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Dhar MS. Station delays, their standard deviations, and event relocations in the Reno-area basin from a dense USArray flexible array deployment during the 2008 west Reno earthquake swarm. [Thesis]. University of Nevada, Reno; 2010. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=1480794
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
2.
Thompson, Mayo.
Analysis of shear wave velocity measurements for prediction uncertainties in Southern California.
Degree: 2010, University of Nevada, Reno
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=1480803
► With the relatively sparse number of direct VS30 measurements in Southern California, researchers have created various proxies to estimate this predictor of ground motion.…
(more)
▼ With the relatively sparse number of direct VS30 measurements in Southern California, researchers have created various proxies to estimate this predictor of ground motion. Utilizing 400 publicly available VS 30 site characterization measurements, the goal of this study is to evaluate the data and spatial uncertainty of VS30 predictions. We calculated VSZ for depths of 10, 30, 50 and 100 m as well as Z500, Z1000, Z1500 for the 82 new site measurements presented in this study. For all 400 publicly available site characterizations, we made predictions based on the Southern California Earthquake Center Community Velocity Model Version 4.0 (Magistrale et al., 2000) and a topographic-slope proxy developed by Wald & Allen (2007). The subsets of our data set, "rock" (44 sites), "soil" (118) and "basin" (238) are based on the site class map of Wills et al. (2000). The mean values of basin and soil subset predictions based on the SCEC CVM are within 5% and 15% respectively when compared to measurement means. Less than half of the soil site predictions are within ±20% of measured values. Less than half of the predictions based on topographic slope are within ±20% of the measured values. Through statistical analysis, a log normal distribution best fits the complete dataset. V S30 and spatial standard deviation maps created from natural-log transformed data show a spatial standard deviation or uncertainty of >0.30 natural-log units in the Los Angeles Basin and >0.38 ln units outside the basin in areas where predictions are made. The spatial uncertainty does not reflect the epistemic uncertainty associated with the measured values. Unlike proxies based on geologic correlation of units, and topographic slope proxies, hazard maps created from indicator kriging show NEHRP hazard class E is likely in the Los Angeles Basin. More dense measurements are feasible and can readily decrease the uncertainty of predictions.
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Thompson, M. (2010). Analysis of shear wave velocity measurements for prediction uncertainties in Southern California. (Thesis). University of Nevada, Reno. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=1480803
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Thompson, Mayo. “Analysis of shear wave velocity measurements for prediction uncertainties in Southern California.” 2010. Thesis, University of Nevada, Reno. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=1480803.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Thompson, Mayo. “Analysis of shear wave velocity measurements for prediction uncertainties in Southern California.” 2010. Web. 23 Apr 2018.
Vancouver:
Thompson M. Analysis of shear wave velocity measurements for prediction uncertainties in Southern California. [Internet] [Thesis]. University of Nevada, Reno; 2010. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=1480803.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Thompson M. Analysis of shear wave velocity measurements for prediction uncertainties in Southern California. [Thesis]. University of Nevada, Reno; 2010. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=1480803
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
University of Oregon
3.
Beachly, Matthew William.
The upper crustal P-wave velocity structure of Newberry volcano, Central Oregon.
Degree: 2011, University of Oregon
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=1497098
► The upper-crustal seismic-velocity structure of Newberry volcano, central Oregon, is imaged using P-wave travel time tomography. The inversion combines a densely-spaced seismic line collected…
(more)
▼ The upper-crustal seismic-velocity structure of Newberry volcano, central Oregon, is imaged using P-wave travel time tomography. The inversion combines a densely-spaced seismic line collected in 2008 with two USGS seismic experiments from the 1980s. A high-velocity ring (7 km EW by 5 km NS) beneath the inner caldera faults suggests an intrusive ring complex 200 to 500 m thick. Within this ring shallow low velocities (<2 km depth) are interpreted as caldera fill and a subsided block. High velocities below 2 km depth could be intrusive complexes. There appears to be a low-velocity body at 3-6 km depth beneath the center of the volcano. This region is poorly resolved in the inversion because the ray paths bend around the low-velocity body. The 2008 data also recorded a secondary arrival that may be a delayed P-wave interacting with the low-velocity body.
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Beachly, M. W. (2011). The upper crustal P-wave velocity structure of Newberry volcano, Central Oregon. (Thesis). University of Oregon. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=1497098
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Beachly, Matthew William. “The upper crustal P-wave velocity structure of Newberry volcano, Central Oregon.” 2011. Thesis, University of Oregon. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=1497098.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Beachly, Matthew William. “The upper crustal P-wave velocity structure of Newberry volcano, Central Oregon.” 2011. Web. 23 Apr 2018.
Vancouver:
Beachly MW. The upper crustal P-wave velocity structure of Newberry volcano, Central Oregon. [Internet] [Thesis]. University of Oregon; 2011. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=1497098.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Beachly MW. The upper crustal P-wave velocity structure of Newberry volcano, Central Oregon. [Thesis]. University of Oregon; 2011. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=1497098
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
University of Oregon
4.
Alba, Sequoia.
ETS in tidal records.
Degree: 2012, University of Oregon
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=1505095
► Uplift rates associated with 12 episodic tremor and slip events on the Cascadia Subduction Zone occurring between 1997 and 2010 have been determined from…
(more)
▼ Uplift rates associated with 12 episodic tremor and slip events on the Cascadia Subduction Zone occurring between 1997 and 2010 have been determined from hourly water level records from 4 NOAA tide gauges (Neah Bay, Port Angeles, Port Townsend, and Seattle). Displacements inferred from water levels generally agree with displacements inferred from modeling GPS data. Examination of uplift between events shows an inter-event deformation rate approximately equal in magnitude, with ETS events, on average, releasing strain accumulated between events, suggesting that ETS is consistent with the elastic rebound theory. Additionally, while the GPS record only extends to the late 1990s and the tremor record includes only recent decades for Cascadia, tidal records in the Pacific Northwest and around the world span many decades. Thus, by showing that ETS can be resolved in tidal records we open up the possibility that tidal records could be used to study ETS where other tools are not available. This thesis contains unpublished coauthored material.
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Alba, S. (2012). ETS in tidal records. (Thesis). University of Oregon. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=1505095
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Alba, Sequoia. “ETS in tidal records.” 2012. Thesis, University of Oregon. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=1505095.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Alba, Sequoia. “ETS in tidal records.” 2012. Web. 23 Apr 2018.
Vancouver:
Alba S. ETS in tidal records. [Internet] [Thesis]. University of Oregon; 2012. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=1505095.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Alba S. ETS in tidal records. [Thesis]. University of Oregon; 2012. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=1505095
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
5.
Frary, Roxanna.
Fault Imaging with High-Resolution Seismic Reflection for Earthquake Hazard and Geothermal Resource Assessment in Reno, Nevada.
Degree: 2012, University of Nevada, Reno
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=1512428
► The Truckee Meadows basin is situated adjacent to the Sierra Nevada microplate, on the western boundary of the Walker Lane. Being in the transition…
(more)
▼ The Truckee Meadows basin is situated adjacent to the Sierra Nevada microplate, on the western boundary of the Walker Lane. Being in the transition zone between a range-front normal fault on the west and northwest-striking right-lateral strike slip faults to the east, there is no absence of faulting in this basin. The Reno-Sparks metropolitan area is located in this basin, and with a significant population living here, it is important to know where these faults are. High-resolution seismic reflection surveys are used for the imaging of these faults along the Truckee River, across which only one fault was previously mapped, and in southern Reno near and along Manzanita Lane, where a swarm of short faults has been mapped. The reflection profiles constrain the geometries of these faults, and suggest additional faults not seen before. Used in conjunction with depth to bedrock calculations and gravity measurements, the seismic reflection surveys provide definitive locations of faults, as well as their orientations. Offsets on these faults indicate how active they are, and this in turn has implications for seismic hazard in the area. In addition to seismic hazard, the faults imaged here tell us something about the conduits for geothermal fluid resources in Reno.
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Frary, R. (2012). Fault Imaging with High-Resolution Seismic Reflection for Earthquake Hazard and Geothermal Resource Assessment in Reno, Nevada. (Thesis). University of Nevada, Reno. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=1512428
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Frary, Roxanna. “Fault Imaging with High-Resolution Seismic Reflection for Earthquake Hazard and Geothermal Resource Assessment in Reno, Nevada.” 2012. Thesis, University of Nevada, Reno. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=1512428.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Frary, Roxanna. “Fault Imaging with High-Resolution Seismic Reflection for Earthquake Hazard and Geothermal Resource Assessment in Reno, Nevada.” 2012. Web. 23 Apr 2018.
Vancouver:
Frary R. Fault Imaging with High-Resolution Seismic Reflection for Earthquake Hazard and Geothermal Resource Assessment in Reno, Nevada. [Internet] [Thesis]. University of Nevada, Reno; 2012. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=1512428.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Frary R. Fault Imaging with High-Resolution Seismic Reflection for Earthquake Hazard and Geothermal Resource Assessment in Reno, Nevada. [Thesis]. University of Nevada, Reno; 2012. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=1512428
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
6.
Ghosh, Attreyee.
Elucidating lithosphere-mantle coupling by modeling the lithospheric stress field and predicting plate motions.
Degree: 2009, State University of New York at Stony Brook
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=3338160
► Even after the establishment of the plate tectonic theory nearly four decades ago, some fundamental questions have still not been satisfactorily answered. What drives…
(more)
▼ Even after the establishment of the plate tectonic theory nearly four decades ago, some fundamental questions have still not been satisfactorily answered. What drives the Earth’s plates? Are plates and mantle coupled, and if so, what is the nature of that coupling? What is the role of density buoyancy-driven flow in driving the plates? These are some of the questions we try to address in our study through a joint modeling of lithosphere dynamics and mantle convection. If the initial coupling model is correct, the predicted stresses will match the observed deformation along the plate boundary zones and the predicted velocities will match the observed plate motions. We model the lithospheric deviatoric stress field from gravitational potential energy (GPE) differences and compare our modeled stress tensor field with velocity gradient tensor field along the Earth’s deforming plate boundary zones (from GSRM). The deviatoric stresses due to active basal tractions acting at the base of the lithosphere, arising from density buoyancy-driven mantle convection, are also compared with the strain rate tensor dataset from GSRM. We find that the combined stresses from lithosphere and mantle buoyancies yield the best fit to the deformation indicators, especially in areas of continental deformation. This is most likely due to driving shear tractions induced by the surrounding mantle, related to the history of subduction in those areas. We also generate plate motions in our convection models by incorporating lateral viscosity variations generated by major geological features of the Earth, such as the continent-ocean divide, the presence of cratonic roots as well as age differences in the oceanic lithosphere. For each structure, we predict the deviatoric stress field, the pattern of poloidal and toroidal flow and the partitioning ratio between toroidal/poloidal velocities. The predicted deviatoric stress field is added to the deviatoric stresses generated by lithosphere buoyancies and the total stress field is compared with strain rate tensor information from GSRM. The best-fit model has to satisfy both the constraints of matching the plate motions and the deviatoric stress field simultaneously. By using both these constraints, we are able to eliminate several types of models and narrow down significantly the set of models that fit the observations.
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Ghosh, A. (2009). Elucidating lithosphere-mantle coupling by modeling the lithospheric stress field and predicting plate motions. (Thesis). State University of New York at Stony Brook. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=3338160
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Ghosh, Attreyee. “Elucidating lithosphere-mantle coupling by modeling the lithospheric stress field and predicting plate motions.” 2009. Thesis, State University of New York at Stony Brook. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=3338160.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Ghosh, Attreyee. “Elucidating lithosphere-mantle coupling by modeling the lithospheric stress field and predicting plate motions.” 2009. Web. 23 Apr 2018.
Vancouver:
Ghosh A. Elucidating lithosphere-mantle coupling by modeling the lithospheric stress field and predicting plate motions. [Internet] [Thesis]. State University of New York at Stony Brook; 2009. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3338160.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Ghosh A. Elucidating lithosphere-mantle coupling by modeling the lithospheric stress field and predicting plate motions. [Thesis]. State University of New York at Stony Brook; 2009. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3338160
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Stanford University
7.
Gashawbeza Mengesha, Ewenet.
Nature of the crust and upper mantle beneath Northwest Basin-and-Range and East Africa using passive-source seismic data.
Degree: 2009, Stanford University
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=3364518
► In this thesis, I present my contribution towards the understanding of rifting processes responsible for the shaping of two tectonic environments. The first region…
(more)
▼ In this thesis, I present my contribution towards the understanding of rifting processes responsible for the shaping of two tectonic environments. The first region of interest is the Basin-and-Ranges province, a region actively deforming in a wide rifting mode, and the second is the Main Ethiopian Rift, a region actively deforming in a narrow rifting mode. The Basin-and-Range Province of western North America is one of the best regions in the world for the study of processes related to continental rifting. It is a broad and elevated region of intracontinental stretching currently extending in a wide rift mode. I primarily focused on the northwest corner of the Basin-and-Range province, which is a transition zone between a highly extended region in the east to a region where there is less extension in the west. The composition and structure of the crust beneath this region and its relationship with the upper-crustal extension is not adequately understood. The Main Ethiopian Rift is part of the East African Rift System, which provides a modern analog to help us understand how continents break apart. The exact mechanism of rift formation is an on-going debate among geologists and geophysicists. Seismic characteristics of the upper-mantle and its relationship with the current rifting processes and volcanism need to be understood. In this research project I demonstrated the use of receiver functions, wide-angle refraction, shear-wave splitting, and tomographic approaches to find answers for the above outstanding questions. For the Basin-and-Range province study I used teleseismic data collected by a Stanford University seismic experiment supplemented by data from nearby USArray and Berkeley digital stations to develop insights into the characteristics of the crust in the northwest corner of the Basin-and-Range province. I combined teleseismic waveform data from a PASSCAL short-period seismic network and the USArray transportable broadband stations to study crustal thickness variations and rock properties beneath the northwest Basin-and-Range region. For the Main Ethiopian Rift study I used data collected during the EAGLE (Ethiopia-Afar Geoscientific Lithospheric Experiment) project and the EBSE (Ethiopian Broadband Seismic Experiment). I used shear-wave splitting measurements to understand the relationship between splitting parameters and interaction of Cenozoic rifting and magmatism with the older Precambrian lithosphere fabrics in Ethiopia. Upper-mantle anisotropy may be caused either by present asthenospheric mantle flow or by frozen signatures of former deformation and stress conditions in the lithosphere. We find that the mantle anisotropy beneath East Africa is more dominated by deformational events in the Proterozoic times occurring within the lithosphere than the present-day processes in the sublithospheric mantle. Consequently, the distribution and magnitude of anisotropy provided valuable data to constrain the role of the mantle in the tectonic…
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Gashawbeza Mengesha, E. (2009). Nature of the crust and upper mantle beneath Northwest Basin-and-Range and East Africa using passive-source seismic data. (Thesis). Stanford University. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=3364518
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Gashawbeza Mengesha, Ewenet. “Nature of the crust and upper mantle beneath Northwest Basin-and-Range and East Africa using passive-source seismic data.” 2009. Thesis, Stanford University. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=3364518.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Gashawbeza Mengesha, Ewenet. “Nature of the crust and upper mantle beneath Northwest Basin-and-Range and East Africa using passive-source seismic data.” 2009. Web. 23 Apr 2018.
Vancouver:
Gashawbeza Mengesha E. Nature of the crust and upper mantle beneath Northwest Basin-and-Range and East Africa using passive-source seismic data. [Internet] [Thesis]. Stanford University; 2009. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3364518.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Gashawbeza Mengesha E. Nature of the crust and upper mantle beneath Northwest Basin-and-Range and East Africa using passive-source seismic data. [Thesis]. Stanford University; 2009. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3364518
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
8.
Goldberg, Daniel N.
Numerical and theoretical treatment of grounding line movement and ice shelf buttressing in marine ice sheets.
Degree: 2009, New York University
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=3365701
► Understanding the dynamics of marine ice sheets is integral to studying the evolution of the Antarctic Ice Sheet in both the short and long…
(more)
▼ Understanding the dynamics of marine ice sheets is integral to studying the evolution of the Antarctic Ice Sheet in both the short and long terms. An important component of the dynamics, grounding line migration, has proved difficult to represent in numerical models, with undesirable behavior such as sensitivity to grid resolution having been observed. Most successful attempts at representing grounding line migration have made use of techniques that are only readily applicable to flowline models, such as Arbitrary Lagrangian-Eulerian schemes. It remains unclear whether a purely Eulerian flowline model can reproduce the actual solution of the governing differential equations, as well as what the theoretical properties of that solution are. In addition, in order to capture the stress transmission involved in another important dynamic component, the buttressing of a marine ice sheet by its ice shelf, the transverse flow direction must also be resolved. Here a numerical model is developed that solves the time-dependent Shelfy-Stream equations [<i>MacAyeal,</i> 1989] and makes use of mesh adaption techniques to overcome the difficulties typically associated with the numerics of grounding line migration. In the special case of a flowline model, it is shown that the Shelfy-Stream equations have a unique solution provided constraints on the initial condition and the forcing are satisfied, and the convergence properties of the model are examined. Model output is also compared with a recent benchmark for flowline models. It is shown that our model yields an accurate solution while using far less resources than would be required without mesh adaption. It is also shown that the mesh adapting techniques extend to two horizontal dimensions. Experiments are carried out to determine how both ice shelf buttressing and ice rises affect the marine instability predicted for an ice sheet on a foredeepened bed. It is found that buttressing is not always sufficient to stabilize such a sheet but collapse of the grounded portion is still greatly delayed. It is also shown that the effect of an ice rise is similar to that of narrowing the ice shelf.
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Goldberg, D. N. (2009). Numerical and theoretical treatment of grounding line movement and ice shelf buttressing in marine ice sheets. (Thesis). New York University. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=3365701
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Goldberg, Daniel N. “Numerical and theoretical treatment of grounding line movement and ice shelf buttressing in marine ice sheets.” 2009. Thesis, New York University. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=3365701.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Goldberg, Daniel N. “Numerical and theoretical treatment of grounding line movement and ice shelf buttressing in marine ice sheets.” 2009. Web. 23 Apr 2018.
Vancouver:
Goldberg DN. Numerical and theoretical treatment of grounding line movement and ice shelf buttressing in marine ice sheets. [Internet] [Thesis]. New York University; 2009. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3365701.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Goldberg DN. Numerical and theoretical treatment of grounding line movement and ice shelf buttressing in marine ice sheets. [Thesis]. New York University; 2009. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3365701
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
University of California, San Diego
9.
Wheelock, Brent David.
Electromagnetic Imaging of the Crust and Upper Mantle across the Continental Margin in Central California.
Degree: 2013, University of California, San Diego
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=3546692
► Electromagnetic methods, particularly magnetotelluric (MT) sounding, are often used to detect fluids in the crust and upper mantle. Recently, MT studies on land have…
(more)
▼ Electromagnetic methods, particularly magnetotelluric (MT) sounding, are often used to detect fluids in the crust and upper mantle. Recently, MT studies on land have focused on the deep structure of the San Andreas fault (SAF) in central California. One of these studies found a region of high conductivity, interpreted as a local abundance of pore fluid, southwest of the fault at depths corresponding to the lower crust and upper mantle. The study also identified a change in the connection of this deep conductor to the root of the SAF as their measurements moved along the strike of the fault. It was proposed that a change in access of fluids to the deep extension of the fault, as evidenced by the modeled resistivity of the region, is responsible for the observed change in behavior of both earthquakes and non-volcanic tremor along the central Californian segment of the SAF. As an effort to extend knowledge of the resistivity structure into the offshore environment of central California, as well as to better constrain the interpretations made onshore, the Marine Electromagnetic Research Group at the Scripps Institution of Oceanography collected marine MT and controlled-source electromagnetic (CSEM) data there. Our single profile of data extends an existing profile of land data. In this dissertation I interpret both profiles of MT data, land and marine, jointly. Inversions of the amphibious dataset produce a resistivity model that is similar to previous results. However, upon closer inspection it was found that the marine data and the land data solicit antithetical structures. I suspected this to be caused by distortion from bathymetry that varies in three dimensions (3D), which is a problem because our 2D models assume that the earth is uniform in the horizontal dimension perpendicular to our profile. Few numerical methods exist to calculate the effects of 3D bathymetry in the necessary detail, so I improved upon an established thin-sheet technique to allow for higher resolution models. With this method I estimated how the effects of 3D bathymetry along our profile deviate from those predicted by an analogous 2D model. The effects are significant relative to the data errors used in inversion. As a test, I created synthetic data from both 2D and 3D bathymetric models, and invert them with a 2D inversion algorithm. Surprisingly, the inversion of 2D data did not recover the simple model used to create the synthetic data. Anomalous structures were introduced that weakly resembled those found in the models derived from actual data. Inversion of the 3D data made matters worse; the same artifacts found with 2D data became more extreme and their resemblance to the features in the results from actual data was enhanced. I concluded that the results from applying the established 2D inversion scheme on the actual data cannot be trusted, as is likely the case for the work on the same data that was previously published by others. The thin-sheet modeling suggests that future interpretations must at…
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Wheelock, B. D. (2013). Electromagnetic Imaging of the Crust and Upper Mantle across the Continental Margin in Central California. (Thesis). University of California, San Diego. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=3546692
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Wheelock, Brent David. “Electromagnetic Imaging of the Crust and Upper Mantle across the Continental Margin in Central California.” 2013. Thesis, University of California, San Diego. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=3546692.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Wheelock, Brent David. “Electromagnetic Imaging of the Crust and Upper Mantle across the Continental Margin in Central California.” 2013. Web. 23 Apr 2018.
Vancouver:
Wheelock BD. Electromagnetic Imaging of the Crust and Upper Mantle across the Continental Margin in Central California. [Internet] [Thesis]. University of California, San Diego; 2013. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3546692.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Wheelock BD. Electromagnetic Imaging of the Crust and Upper Mantle across the Continental Margin in Central California. [Thesis]. University of California, San Diego; 2013. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3546692
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
University of California, Berkeley
10.
Wiseman, Kelly Grijalva.
The Far Reach of Megathrust Earthquakes| Evolution of Stress, Deformation and Seismicity Following the 2004 Sumatra-Andaman Rupture.
Degree: 2013, University of California, Berkeley
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=3556000
► Starting with the 2004 <i>M</i>w 9.2 megathrust event, Southeast Asia has been home to an exceptional amount of seismic activity over the past eight…
(more)
▼ Starting with the 2004 <i>M</i>w 9.2 megathrust event, Southeast Asia has been home to an exceptional amount of seismic activity over the past eight years. The series of megathrust earthquakes have been imperfect dominoes, rupturing the northernmost section of the Sunda subduction zone in 2004, then the Nias segment next in line to the south in 2005, followed by the Bengkulu earthquake ∼750 km further south in 2007. The Bengkulu earthquake skipped over the northern Mentawai segment, which has not ruptured in a great event since 1797. However, the subduction zone has not been silent is this section. Analysis of focal mechanisms and geodetic data reveals the reactivation of the Mentawai backthrust system in the overriding plate, and a large, deep earthquake near the city of Padang in 2009 is shown through finite fault inversions and aftershock analysis to have obliquely ruptured the subducting slab. At the same time, the entire region spanning from the Indian Ocean, through the trench and forearc islands, and throughout Thailand has been aseismically deforming in response to the stress changes in the mantle following the megathrust earthquakes. Geodetic observations of postseismic deformation during the first five years following the 2004 earthquake have shown that the far-field regions of Thailand and the Malay Peninsula have moved more postseismically than coseismically, peaking at ∼0.4 m of horizontal displacement in Phuket. In 2012, the stress changes associated with this continued postseismic deformation, along with the initial push from the megathrust earthquakes, appears to have triggered the largest instrumentally recorded strike-slip earthquake. This was a complex earthquake, consisting of four conjugate fault segments, that ruptured the diffuse India-Australia plate boundary zone. Understanding how the faults interact throughout the subduction system, from the incoming plate, to the slab, to the megathrust interface, and overriding plate is an essential part of determining the future seismic hazard for Southeast Asia.
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Wiseman, K. G. (2013). The Far Reach of Megathrust Earthquakes| Evolution of Stress, Deformation and Seismicity Following the 2004 Sumatra-Andaman Rupture. (Thesis). University of California, Berkeley. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=3556000
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Wiseman, Kelly Grijalva. “The Far Reach of Megathrust Earthquakes| Evolution of Stress, Deformation and Seismicity Following the 2004 Sumatra-Andaman Rupture.” 2013. Thesis, University of California, Berkeley. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=3556000.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Wiseman, Kelly Grijalva. “The Far Reach of Megathrust Earthquakes| Evolution of Stress, Deformation and Seismicity Following the 2004 Sumatra-Andaman Rupture.” 2013. Web. 23 Apr 2018.
Vancouver:
Wiseman KG. The Far Reach of Megathrust Earthquakes| Evolution of Stress, Deformation and Seismicity Following the 2004 Sumatra-Andaman Rupture. [Internet] [Thesis]. University of California, Berkeley; 2013. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3556000.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Wiseman KG. The Far Reach of Megathrust Earthquakes| Evolution of Stress, Deformation and Seismicity Following the 2004 Sumatra-Andaman Rupture. [Thesis]. University of California, Berkeley; 2013. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3556000
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
11.
Yang, Hongfeng.
Study of earthquake fault zone structures by aftershock location and high-frequency waveform modeling.
Degree: 2010, Saint Louis University
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=3419780
► In this study, I analyzed high frequency waveforms of local earthquakes to map crustal faults and to investigate fine structures of fault zone (FZ).…
(more)
▼ In this study, I analyzed high frequency waveforms of local earthquakes to map crustal faults and to investigate fine structures of fault zone (FZ). In order to determine the fault plane of the 18 April 2008 Illinois earthquake, I first developed a sliding-window cross-correlation (SCC) detection technique and applied the technique to continuous waveforms recorded by the Cooperative New Madrid Seismic Network stations. The technique detected more than 120 aftershocks down to ML 1.0 in the 2 week time window following the mainshock, which is three times more than the number of aftershocks reported by the seismic network. Most aftershocks happened within 24 hrs of the mainshock. I then relocated all events by the double-difference relocation algorithm. Accurate <i>P</i>- and <i>S</i>-wave differential arrival times between events were obtained by waveform cross correlation. After relocation, I used the L1 norm to fit all located events by a plane to determine the mainshock fault plane. The best-fit plane has a strike of 292°±11° and dips 81°±11° to the northeast. This plane agrees well with the focal mechanism solutions of the mainshock and four largest aftershocks. By combining the aftershock locations and focal mechanism solutions, I concluded that the 18 April earthquake occurred on a nearly vertical left-lateral strike-slip fault orienting in the west-northwest-east-southeast direction. The fault coincides with the proposed left-stepping Divide accommodation zone in the La Salle deformation belt and indicates reactivation of old deformation zone by contemporary stresses in the Midcontinent. To investigate fine structures of the San Jacinto fault zone and the Calico fault zone in southern California, I used <i>P</i>- and <i> S</i>-wave travel times and waveforms of local earthquakes recorded by temporary arrays across the faults. In the San Jacinto fault zone study, I developed a method to determine the depth extent of the low-velocity zone (LVZ) associated with a FZ using <i>S</i>-wave precursors. The precursors are diffracted <i>S</i> waves around the edges of LVZ and their relative amplitudes to the direct <i>S</i> waves are sensitive to LVZ depth. I applied the method to data recorded by three temporary arrays across three branches of the San Jacinto fault zone. The FZ dip was constrained by differential travel times of <i>P</i> waves between stations at two side of the FZ. Other FZ parameters (width and velocity contrast) were determined by modelling waveforms of direct and FZ-reflected <i>P</i> and <i>S</i> waves. I found that the LVZ of the Buck Ridge fault branch has a width of ∼150 m with a 30–40 per cent reduction in <i> Vp</i> and a 50–60 per cent reduction in <i>V s</i>. The fault dips 70° to southwest and its LVZ extends only to 2±1 km in depth. The LVZ of the Clark Valley fault branch has a width of ∼200 m with 40 per cent reduction in <i>Vp</i> and 50 per cent reduction in <i>Vs</i>.…
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Yang, H. (2010). Study of earthquake fault zone structures by aftershock location and high-frequency waveform modeling. (Thesis). Saint Louis University. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=3419780
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Yang, Hongfeng. “Study of earthquake fault zone structures by aftershock location and high-frequency waveform modeling.” 2010. Thesis, Saint Louis University. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=3419780.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Yang, Hongfeng. “Study of earthquake fault zone structures by aftershock location and high-frequency waveform modeling.” 2010. Web. 23 Apr 2018.
Vancouver:
Yang H. Study of earthquake fault zone structures by aftershock location and high-frequency waveform modeling. [Internet] [Thesis]. Saint Louis University; 2010. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3419780.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Yang H. Study of earthquake fault zone structures by aftershock location and high-frequency waveform modeling. [Thesis]. Saint Louis University; 2010. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3419780
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
University of Southern California
12.
Bailey, Iain W.
Heterogeneity of earthquake stress drops, focal mechanisms and active fault zones.
Degree: 2009, University of Southern California
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=3368693
► Faults and fault networks are heterogeneous structures where elastic strain from ongoing tectonic motions is released in earthquakes. Three studies presented in this thesis…
(more)
▼ Faults and fault networks are heterogeneous structures where elastic strain from ongoing tectonic motions is released in earthquakes. Three studies presented in this thesis aim to illustrate the importance of fault heterogeneity using numerical models and quantify fault heterogeneity using earthquake data. In the first part, a model fault consisting of a grid of discrete slip patches surrounded by a 3-D elastic half-space is used to investigate the statistics of earthquake stress drops. Predictions for stress drops on a homogeneous fault with properties constrained by experiments are an order of magnitude larger than typical observations from seismic data. In the model, heterogeneous frictional properties result in an evolving distribution of spatially heterogeneous stress. Since stress must exceed the fault strength only in the hypocenter region, lower average stress at times of rupture lead to stress drops consistently lower than predictions for a homogeneous fault. The second part of the thesis concerns quantifying the geometry of earthquake faulting for different spatial scales and magnitude ranges in a plate boundary region. We compute and compare potency tensor summations of subsets of a catalog containing ∼ 170,00 focal mechanisms for 0 < <i>ML</i> ≤ 5 earthquakes from southern California. Results indicate that earthquake deformation is influenced by scales related to plate tectonic motions (∼ 700 km), large scale fault zones (∼ 50–250 km) and smaller geometric complexities (∼ 5–50 km). However, individual fault zone length-scales have distinct characteristics, indicating departure from self-similarity despite the lack of a single characteristic length-scale. In the third part of the thesis higher quality focal mechanisms are used to compare levels of heterogeneity between nine strike-slip fault zones in California. Focal mechanism heterogeneity is quantified using two measures that represent the scatter and asymmetry in faulting orientations, both computed from normalized potency tensor summations. The scatter correlates with complexity of the fault surface traces, and asymmetry correlates with the dominant fault orientation relative to plate motion directions. These observations indicate that focal mechanism heterogeneity relates both the long term evolutionary properties of the fault zone and the ability of the fault to efficiently release plate tectonic strains.
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Bailey, I. W. (2009). Heterogeneity of earthquake stress drops, focal mechanisms and active fault zones. (Thesis). University of Southern California. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=3368693
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Bailey, Iain W. “Heterogeneity of earthquake stress drops, focal mechanisms and active fault zones.” 2009. Thesis, University of Southern California. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=3368693.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Bailey, Iain W. “Heterogeneity of earthquake stress drops, focal mechanisms and active fault zones.” 2009. Web. 23 Apr 2018.
Vancouver:
Bailey IW. Heterogeneity of earthquake stress drops, focal mechanisms and active fault zones. [Internet] [Thesis]. University of Southern California; 2009. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3368693.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Bailey IW. Heterogeneity of earthquake stress drops, focal mechanisms and active fault zones. [Thesis]. University of Southern California; 2009. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3368693
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
13.
Yano, Tomoko Elizabeth.
Kinematic Earthquake Sources of High and Low Frequencies and Their Relation to Earth Structure.
Degree: 2013, University of California, Santa Barbara
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=3553796
► In this thesis, we studied the earthquake process from a dual perspective: i.e. modeling the complex Earth medium and the earthquake dislocations at the…
(more)
▼ In this thesis, we studied the earthquake process from a dual perspective: i.e. modeling the complex Earth medium and the earthquake dislocations at the source. These two fundamental aspects define the ground motion. Existing kinematic source models are essentially based on the low frequencies contained in the seismic signals (< 1 Hz). Due to our limited knowledge of the Earth medium, the high frequencies in the seismic signals are difficult to be modeled properly. In order to optimize our understanding of the complex earthquake rupture process, a synthesis of both the Earth medium and source model is required. For modeling the complex Earth medium, we developed a tomographic method that exploits the ellipticity of the fundamental Rayleigh wave (ZH ratio). This method enables us to constrain the shear-wave velocity in a narrower target depth range than conventional methods. The ZH ratio method has been applied to the crust and upper mantle beneath the GEOSCOPE stations. The results show that low-velocity zones exist beneath some stations near hotspots. The ZH ratio was applied to the L'Aquila basin area to constrain the shallow velocity structure prior to a kinematic source inversion of the 2009 L'Aquila earthquake. Because of differences in the slip models derived from seismological or geodetic data, we introduced a new strategy to differentiate between slip that occurs co-seismically and that occurs as early post-seismic afterslip. The results suggest that the co-seismic rupture was followed by a slow-slip event with significant moment release in the first day. Lastly, we discussed the development of a back-propagation method to map high-frequency spatial-temporal seismic wave radiation sources onto the fault plane. The new approach considers the free surface reverberations and the fault geometry while existing methods doesn't. Based on results from a synthetic test, we demonstrate that the new back-propagation method is better than existing back-projection method because it not only can locate the spatial-temporal locations of the target sources but also can fairly well recover their amplitudes.
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Yano, T. E. (2013). Kinematic Earthquake Sources of High and Low Frequencies and Their Relation to Earth Structure. (Thesis). University of California, Santa Barbara. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=3553796
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Yano, Tomoko Elizabeth. “Kinematic Earthquake Sources of High and Low Frequencies and Their Relation to Earth Structure.” 2013. Thesis, University of California, Santa Barbara. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=3553796.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Yano, Tomoko Elizabeth. “Kinematic Earthquake Sources of High and Low Frequencies and Their Relation to Earth Structure.” 2013. Web. 23 Apr 2018.
Vancouver:
Yano TE. Kinematic Earthquake Sources of High and Low Frequencies and Their Relation to Earth Structure. [Internet] [Thesis]. University of California, Santa Barbara; 2013. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3553796.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Yano TE. Kinematic Earthquake Sources of High and Low Frequencies and Their Relation to Earth Structure. [Thesis]. University of California, Santa Barbara; 2013. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3553796
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
University of Alaska Fairbanks
14.
Habermann, Marijke.
Basal shear strength inversions for ice sheets with an application to Jakobshavn Isbrae, Greenland.
Degree: 2014, University of Alaska Fairbanks
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=3607054
► Satellite and <i>in situ</i> observations of ice sheet outlet glaciers around the turn of the 21st century showed that rapid changes in ice dynamics…
(more)
▼ Satellite and <i>in situ</i> observations of ice sheet outlet glaciers around the turn of the 21st century showed that rapid changes in ice dynamics are possible and important for the evolution of ice sheets. When attempting to model these dynamic changes the conditions at the ice-bed interface are crucial. Inverse methods can be used to infer basal properties, such as the basal yield stress, from abundant surface velocity observations by using a physical model of ice flow. Inverse methods are very powerful, but they need to be applied with care, otherwise errors can dominate the solution. In this study we investigate the potentials and caveats of inverse methods. Synthetic experiments can be designed where basal conditions are assumed and an ice flow model is used to produce a set of 'synthetic' surface velocities. These can then be used to examine and evaluate inverse methods. We find that in iterative inverse methods it is essential to use a stopping criterion that will prevent overfitting the data. We introduce a new and rapidly-converging iterative inverse method called Incomplete Gauss Newton method, where the linearized problem is partly minimized in each step. In a practical application of inverse methods to the terminus region of Jakobshavn Isbræ, Greenland we investigate changes in basal conditions over time by performing inversions for different years of available surface velocity data. We find a decrease in basal yield stress in the lower areas of the glacier that agrees with effective pressure changes due to the changes in ice geometry. This supports an ocean and terminus driven system. The difference between the modeled and observed velocity fields, called residual, contains information about the ability to reproduce the velocities when only adjustment of the basal condition is allowed. With a properly regularized inversion the residual patterns can be used to investigate sources of error in the system. We find that the ice geometry and the model simplifications influence the ability to reproduce observed velocity fields more than the error in observed velocity does. This indicates that further progress must come from model improvements and improved capabilities to measure bedrock geometry.
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Habermann, M. (2014). Basal shear strength inversions for ice sheets with an application to Jakobshavn Isbrae, Greenland. (Thesis). University of Alaska Fairbanks. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=3607054
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Habermann, Marijke. “Basal shear strength inversions for ice sheets with an application to Jakobshavn Isbrae, Greenland.” 2014. Thesis, University of Alaska Fairbanks. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=3607054.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Habermann, Marijke. “Basal shear strength inversions for ice sheets with an application to Jakobshavn Isbrae, Greenland.” 2014. Web. 23 Apr 2018.
Vancouver:
Habermann M. Basal shear strength inversions for ice sheets with an application to Jakobshavn Isbrae, Greenland. [Internet] [Thesis]. University of Alaska Fairbanks; 2014. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3607054.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Habermann M. Basal shear strength inversions for ice sheets with an application to Jakobshavn Isbrae, Greenland. [Thesis]. University of Alaska Fairbanks; 2014. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3607054
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
15.
Arogundade, Simisola M.
Numerical modeling of ambient noise seismic interferometry.
Degree: 2016, Michigan Technological University
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=10125274
► CO2 sequestration involves storing CO2 in a deep geological formation and may help to mitigate the increasing emission of carbon. To monitor the migration…
(more)
▼ CO2 sequestration involves storing CO2 in a deep geological formation and may help to mitigate the increasing emission of carbon. To monitor the migration of injected fluid in the reservoir, seismic observations may be used to observe changes in reflection character. Conventional methods to image the subsurface, using active seismic measurements, with man-made sources, have been applied at a few test sites, and the use of passive measurements, with natural sources, has been considered as a probable cost-efficient method to monitor CO2 migration and leakage. This numerical modeling study examines the use of seismic interferometry to retrieve weak seismic reflections from background noise, a form of passive monitoring. The factors that influence the quality of the retrieved reflections from interferometry include geophone interval, geophone depth, and effect of shallow noise sources, assuming we seek reflections from deep noise sources, representing either teleseismic events or local events as expected in a field of active injection. Using model data, geophone interval had no significant effect on the reflection quality, but buried geophones produce ghost reflections, suggesting that shallow geophones might be optimal. Shallow noise sources produce a destructive effect on the reflections from deeper noise sources and damage the resulting image.
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Arogundade, S. M. (2016). Numerical modeling of ambient noise seismic interferometry. (Thesis). Michigan Technological University. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=10125274
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Arogundade, Simisola M. “Numerical modeling of ambient noise seismic interferometry.” 2016. Thesis, Michigan Technological University. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=10125274.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Arogundade, Simisola M. “Numerical modeling of ambient noise seismic interferometry.” 2016. Web. 23 Apr 2018.
Vancouver:
Arogundade SM. Numerical modeling of ambient noise seismic interferometry. [Internet] [Thesis]. Michigan Technological University; 2016. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=10125274.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Arogundade SM. Numerical modeling of ambient noise seismic interferometry. [Thesis]. Michigan Technological University; 2016. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=10125274
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
16.
Kawasaki, Kazuo.
Paleomagnetism and Rock Magnetism of "SEDEX" Zn-Pb-Cu Ores
in Black Shales in Australia and Yukon and of Fluorite Veins in
Granite in Newfoundland.
Degree: PhD, Geology, 2011, National Library of Canada
URL: http://scholar.uwindsor.ca/etd/445
► The paleomagnetic age dating technique is used to study the genesis of a fluorite and four "sedimentary exhalative (SEDEX)" deposits which are hard to date…
(more)
▼ The paleomagnetic age dating technique is
used to study the genesis of a fluorite and four "sedimentary
exhalative (SEDEX)" deposits which are hard to date by conventional
radiometric methods because they lack suitable minerals, which
causes controversy about their ore genesis. Paleomagnetic analysis
of 359 specimens from the Devonian St. Lawrence Granite and
fluorite veins in Newfoundland shows that the granite and fluorite
veins are coeval and retain a primary remanence carried by
pyrrhotite and/or magnetite. The difference between the measured
and expected paleopoles is attributed to postemplacement
counterclockwise rotation of ~17░ of the area about a vertical axis
during the Late Devonian Acadian Orogeny. Paleomagnetic analysis of
333 specimens from the Century Zn-Pb-Ag deposit in Australia
isolates a stable characteristic remanent magnetization (ChRM) for
ore sites only that resides mainly in single (SD) or pseudosingle
domain (PSD) titanomagnetite and pyrrhotite. A positive fold test
shows that the ores ChRM predates D2 deformation in the
Mesoproterozoic Isan Orogeny. The paleomagnetic age of 1558▒4 Ma
supports a late diagenetic replacement model for ore genesis.
Paleomagnetic and rock magnetic analyses of 333 specimens from the
Mount Isa Zn-Pb-Cu-Ag and George Fisher Zn-Pb-Ag deposits in
Australia isolate a stable ChRM carried mainly by SD or PSD
pyrrhotite and/or titanomagnetite. The negative fold test shows
that the ChRM postdates the ~1510 Ma D3 deformation in the Isan
Orogeny. Thus the ~1505 Ma paleomagnetic age provides a minimum age
for the ores and an age for the greenschist metamorphism during the
orogeny. Paleomagnetic and rock magnetic analyses of 339 specimens
from six mineralized panels in the Howards Pass Zn-Pb deposits in
Yukon isolate a stable ChRM that mainly resides in SD or PSD
pyrrhotite and titanomagnetite. The paleopole falls on Middle
Jurassic portion of the North American apparent polar wander path
(APWP) or corrected APWP for the Intermontane terranes, giving ~170
Ma and ~162 Ma, respectively. The results indicate that the Selwyn
Basin had undergone ~35░ clockwise rotation with ~10░ northward
translation between Middle Jurassic and
mid-Cretaceous.
Advisors/Committee Members: Symons, David (Earth and Environmental Sciences).
Subjects/Keywords: Geophysics.
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Kawasaki, K. (2011). Paleomagnetism and Rock Magnetism of "SEDEX" Zn-Pb-Cu Ores
in Black Shales in Australia and Yukon and of Fluorite Veins in
Granite in Newfoundland. (Doctoral Dissertation). National Library of Canada. Retrieved from http://scholar.uwindsor.ca/etd/445
Chicago Manual of Style (16th Edition):
Kawasaki, Kazuo. “Paleomagnetism and Rock Magnetism of "SEDEX" Zn-Pb-Cu Ores
in Black Shales in Australia and Yukon and of Fluorite Veins in
Granite in Newfoundland.” 2011. Doctoral Dissertation, National Library of Canada. Accessed April 23, 2018.
http://scholar.uwindsor.ca/etd/445.
MLA Handbook (7th Edition):
Kawasaki, Kazuo. “Paleomagnetism and Rock Magnetism of "SEDEX" Zn-Pb-Cu Ores
in Black Shales in Australia and Yukon and of Fluorite Veins in
Granite in Newfoundland.” 2011. Web. 23 Apr 2018.
Vancouver:
Kawasaki K. Paleomagnetism and Rock Magnetism of "SEDEX" Zn-Pb-Cu Ores
in Black Shales in Australia and Yukon and of Fluorite Veins in
Granite in Newfoundland. [Internet] [Doctoral dissertation]. National Library of Canada; 2011. [cited 2018 Apr 23].
Available from: http://scholar.uwindsor.ca/etd/445.
Council of Science Editors:
Kawasaki K. Paleomagnetism and Rock Magnetism of "SEDEX" Zn-Pb-Cu Ores
in Black Shales in Australia and Yukon and of Fluorite Veins in
Granite in Newfoundland. [Doctoral Dissertation]. National Library of Canada; 2011. Available from: http://scholar.uwindsor.ca/etd/445
17.
Runyan, Taylor E.
A Machine Learning Approach to Quantifying Likely Locations of Gas and Gas Hydrate Accumulation.
Degree: 2017, University of Louisiana at Lafayette
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=10268964
► Gas hydrates, specifically methane hydrates, are sparsely sampled on a global scale, and their accumulation is difficult to predict geospatially. Several attempts have been…
(more)
▼ Gas hydrates, specifically methane hydrates, are sparsely sampled on a global scale, and their accumulation is difficult to predict geospatially. Several attempts have been made at estimating global inventories, and to some extent geospatial distribution, using geospatial extrapolations guided with geophysical and geochemical methods. The objective is to quantitatively predict seafloor total organic carbon and subsequently the geospatial likelihood of encountering methane hydrates. Predictions of TOC are produced using a sparsely observed dataset (Seiter et al., 2004) through a k-nearest neighbor (KNN) algorithm using 423 predictors and 7 nearest neighbors. KNN is unsupervised and non-parametric, as I do not provide any interpretive influence on prior probability distribution, so results are strictly data-driven. This TOC prediction, along with other global datasets (seafloor temperature, pressure, sediment thickness, and crustal heat flow) are used as parameters to train a KNN algorithm in identifying likely locations of methane and/or methane hydrate accumulation. I have selected as test sites several locations where gas hydrates have been well studied, each with significantly different geologic settings. These are: The Blake Ridge (U.S. East Coast), Hydrate Ridge (U.S. West Coast), and the Gulf of Mexico. I then use KNN to quantify similarities between these sites via the normalized distance in parameter space. Results on identification of likely methane and/or methane hydrate accumulation indicate the use of KNN as an unreliable method of identifying accumulation. However, global seafloor TOC predictions are reasonably accurate and have been incorporated to provide a potential analysis on hydrocarbon accumulation.
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Runyan, T. E. (2017). A Machine Learning Approach to Quantifying Likely Locations of Gas and Gas Hydrate Accumulation. (Thesis). University of Louisiana at Lafayette. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=10268964
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Runyan, Taylor E. “A Machine Learning Approach to Quantifying Likely Locations of Gas and Gas Hydrate Accumulation.” 2017. Thesis, University of Louisiana at Lafayette. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=10268964.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Runyan, Taylor E. “A Machine Learning Approach to Quantifying Likely Locations of Gas and Gas Hydrate Accumulation.” 2017. Web. 23 Apr 2018.
Vancouver:
Runyan TE. A Machine Learning Approach to Quantifying Likely Locations of Gas and Gas Hydrate Accumulation. [Internet] [Thesis]. University of Louisiana at Lafayette; 2017. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=10268964.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Runyan TE. A Machine Learning Approach to Quantifying Likely Locations of Gas and Gas Hydrate Accumulation. [Thesis]. University of Louisiana at Lafayette; 2017. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=10268964
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Colorado School of Mines
18.
Munoz, Andrew.
Automatic simultaneous multiple-well ties.
Degree: 2014, Colorado School of Mines
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=1553902
► Well logs, measured in depth, must be tied to seismograms, processed in time, using a time-depth function. Well ties are commonly computed using manual…
(more)
▼ Well logs, measured in depth, must be tied to seismograms, processed in time, using a time-depth function. Well ties are commonly computed using manual techniques, and are therefore prone to human error. I first introduce an automatic single-well tie method that uses smooth dynamic time warping to compute time shifts that align a synthetic seismogram with a seismic trace. These time shifts are constrained to be smoothly varying. I also show that these well ties, in my example, are insensitive to the complexity of my synthetic seismogram modeling. Tying multiple wells compounds errors in single well ties, and maintaining consistency among multiple single well ties is difficult. I introduce an automatic approach to tying multiple wells that improves consistency among well ties. I first model synthetic seismograms for each well. I then create a synthetic image by interpolating the synthetic seismograms between the wells and along seismic image structure. I use smooth dynamic image warping to align the synthetic image to the seismic image and compute updated time-depth functions for each well. I then interpolate the updated time-depth functions between the wells, and map the time-migrated seismic image to depth.
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Munoz, A. (2014). Automatic simultaneous multiple-well ties. (Thesis). Colorado School of Mines. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=1553902
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Munoz, Andrew. “Automatic simultaneous multiple-well ties.” 2014. Thesis, Colorado School of Mines. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=1553902.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Munoz, Andrew. “Automatic simultaneous multiple-well ties.” 2014. Web. 23 Apr 2018.
Vancouver:
Munoz A. Automatic simultaneous multiple-well ties. [Internet] [Thesis]. Colorado School of Mines; 2014. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=1553902.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Munoz A. Automatic simultaneous multiple-well ties. [Thesis]. Colorado School of Mines; 2014. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=1553902
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Colorado School of Mines
19.
Luo, Simon S.
Improved methods of reflection seismic data processing for velocity estimation, imaging, and interpretation.
Degree: 2015, Colorado School of Mines
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=3668324
► Seismic images and the geologic information they provide contribute significantly to our understanding of the earth's subsurface. In this thesis, I focus on methods…
(more)
▼ Seismic images and the geologic information they provide contribute significantly to our understanding of the earth's subsurface. In this thesis, I focus on methods relevant for constructing and interpreting seismic images, including methods for velocity estimation, seismic imaging, and interpretation, which together address key aspects of reflection seismic data processing. Specifically, I propose improved methods for semblance-based normal-moveout velocity analysis, for seismic imaging by least-squares migration, and for the automatic extraction of geologic horizons. To compute a seismic image, an estimate of the subsurface velocity is needed. One common method for constructing an initial velocity model is semblance-based normal-moveout (NMO) velocity analysis, in which semblance spectra are analyzed to identify peaks in semblance corresponding to effective NMO velocities. The accuracy of NMO velocities obtained from semblance spectra depends on the sensitivity of semblance to changes in velocity. By introducing a weighting function in the semblance calculation, I emphasize terms that are more sensitive to velocity changes, which, as a result, increases the resolution of semblance spectra and allows for more accurate NMO velocity estimates. Following velocity analysis, a seismic image of the subsurface is computed by migrating the recorded data. However, while velocity analysis is an important step in processing reflection seismic data, in practice we expect errors in the velocity models we compute, and these errors can degrade a seismic image. Instead of minimizing the difference between predicted and observed seismic data as is done for conventional migration, I propose to minimize the difference between predicted and time-shifted observed data, where the time shifts are the traveltime differences between predicted and observed data. With this misfit function, an image computed for an erroneous velocity model contains features similar to those obtained using a more accurate velocity. Once a seismic image is computed, a common task in interpreting the image is the identification of geologic horizons. As an alternative to manual picking or autotracking, I propose methods to automatically and simultaneously extract all horizons within an image. To extract geologic horizons, a seismic image is unfaulted and unfolded to restore horizons to an undeformed, horizontal state from which they can be easily identified and extracted.
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Luo, S. S. (2015). Improved methods of reflection seismic data processing for velocity estimation, imaging, and interpretation. (Thesis). Colorado School of Mines. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=3668324
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Luo, Simon S. “Improved methods of reflection seismic data processing for velocity estimation, imaging, and interpretation.” 2015. Thesis, Colorado School of Mines. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=3668324.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Luo, Simon S. “Improved methods of reflection seismic data processing for velocity estimation, imaging, and interpretation.” 2015. Web. 23 Apr 2018.
Vancouver:
Luo SS. Improved methods of reflection seismic data processing for velocity estimation, imaging, and interpretation. [Internet] [Thesis]. Colorado School of Mines; 2015. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3668324.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Luo SS. Improved methods of reflection seismic data processing for velocity estimation, imaging, and interpretation. [Thesis]. Colorado School of Mines; 2015. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3668324
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Indiana University
20.
Bauer, Mark.
The seismic structure of southeast Alaska.
Degree: 2014, Indiana University
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=3611120
► The convergent motion of the Pacific and North American Plates in Alaska has produced geologic features associated with subduction zones and has transported displaced…
(more)
▼ The convergent motion of the Pacific and North American Plates in Alaska has produced geologic features associated with subduction zones and has transported displaced terranes along the Queen Charlotte-Fairweather fault system that forms the northeastern boundary of the Pacific Plate. These subduction features stop abruptly at the edge of the Yakutat Block displaced terrane, approximately 300 km from the Queen Charlotte-Fairweather fault. The purpose of this study was to determine the type and geometry of the boundary between the Yakutat Block and North American as well as the cause of the offset volcanic arc and missing Wadati-Benioff zone. I calculated P and S-wave receiver functions for 57 broadband seismic stations located in southeast Alaska. S-wave data was migrated using a Common Conversion Point procedure. P-wave data was imaged via a three-dimensional, pre-stack migration using plane-wave decomposition weighted by an inverse generalized Radon transform to calculate the scattering potential for each event. I also calculated the temperatures at the top of the Yakutat slab and mantle wedge using three different analytical thermal models. The 3-D images and animations I produced show that the Yakutat Block is being subducted, continuous with the Pacific slab, and extends to the Queen Charlotte-Fairweather strike-slip fault systems. The subducted slab extends north to the Wrangell Volcanic Field with a dip than increases gradually from 10° in the west to 15° in the east, stripping approximately 15 km of overlying sediments. The location of the Wrangell Volcanic Field and lack of Wadati-Benioff zone are consistent with the temperatures I calculated for the top of slab and mantle wedge after stripping 15 km of sediment.
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Bauer, M. (2014). The seismic structure of southeast Alaska. (Thesis). Indiana University. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=3611120
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Bauer, Mark. “The seismic structure of southeast Alaska.” 2014. Thesis, Indiana University. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=3611120.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Bauer, Mark. “The seismic structure of southeast Alaska.” 2014. Web. 23 Apr 2018.
Vancouver:
Bauer M. The seismic structure of southeast Alaska. [Internet] [Thesis]. Indiana University; 2014. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3611120.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Bauer M. The seismic structure of southeast Alaska. [Thesis]. Indiana University; 2014. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3611120
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Colorado School of Mines
21.
Douma, Johannes.
Improved temporal and spatial focusing using deconvolution| theoretical, numerical and experimental studies.
Degree: 2014, Colorado School of Mines
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=1554397
► Time Reversal can be used to time reverse and propagate the measured scattered wave- forms to a point in both time and space, ideally…
(more)
▼ Time Reversal can be used to time reverse and propagate the measured scattered wave- forms to a point in both time and space, ideally to a delta function δ([special characters omitted])δ(t). This is commonly referred to as time reversal focusing and has led to time reversal being applied in a wide variety of fields such as medicine, communications, nondestructive evaluation (NDE), and seismology. In practice, time reversal is not optimal for generating a delta function focus if certain conditions are not upheld. For time reversal to work perfectly, the following four conditions must be present: (1) one must record for an infinitely long period of time; (2) Green's functions must be assumed to contain infinite bandwidth; (3) attenuation must be absent within the medium; and (4) one must have full coverage of the wavefield. Due to the need for these conditions, much research is being carried out in order to enhance the time reversal process in practice. We introduce deconvolution, a simple and robust approach, in order to calculate an optimal signal for back propagation designed to give an improved focus. We demonstrate experimentally that deconvolution is able to dramatically improve the temporal focus com- pared to time reversal. Through a joint project with Los Alamos National Laboratory, we compared time reversal to deconvolution. The results showed that deconvolution was able to dramatically improve the temporal focus for a source and a receiver which were both located on the surface of our object. We then continued our experimental studies of deconvolution by doing a joint project with researcher Dr. Ernst Niederleithinger from the Federal Institute for Materials Research and Testing (BAM). For this experiment, we placed multiple sources within a concrete block and recorded the source wavefields on the surface with a single re- ceiver. This experiment was designed to further test the robust nature of deconvolution and compare its temporal focusing capability to that of time reversal. All of these experimental studies show that deconvolution was able to improve the temporal focus compared to time reversal. We continued our comparison study between time reversal and deconvolution and demon- strated theoretically, experimentally, and numerically that deconvolution also improves spa- tial focusing. We give a proof explaining why one would expect improved spatial focusing when there is improved temporal focusing for both a acoustic and elastic media. We then demonstrate in our experiments the improved spatial focus achieved using deconvolution by scanning around the source location with a laser vibrometer at the time of focus for an acoustic case. Finally, we use deconvolution to locate synthetic microseismic events to prove numerically that improved temporal focusing leads to improved spatial focusing for both acoustic and elastic media.
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Douma, J. (2014). Improved temporal and spatial focusing using deconvolution| theoretical, numerical and experimental studies. (Thesis). Colorado School of Mines. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=1554397
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Douma, Johannes. “Improved temporal and spatial focusing using deconvolution| theoretical, numerical and experimental studies.” 2014. Thesis, Colorado School of Mines. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=1554397.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Douma, Johannes. “Improved temporal and spatial focusing using deconvolution| theoretical, numerical and experimental studies.” 2014. Web. 23 Apr 2018.
Vancouver:
Douma J. Improved temporal and spatial focusing using deconvolution| theoretical, numerical and experimental studies. [Internet] [Thesis]. Colorado School of Mines; 2014. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=1554397.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Douma J. Improved temporal and spatial focusing using deconvolution| theoretical, numerical and experimental studies. [Thesis]. Colorado School of Mines; 2014. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=1554397
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
22.
Bianco, Ronald.
The Effects of Fluid Flow On Shear Localization and Frictional Strength From Dynamic Models Of Fault Gouge During Earthquakes.
Degree: 2013, Texas Digital Library
URL: http://hdl.handle.net/1969;
http://hdl.handle.net/2249.1/66720
► This thesis explores the effects of fluid flow on shear localization and frictional strength of fault gouge through the use of a coupled 2-phase (pore…
(more)
▼ This thesis explores the effects of fluid flow on shear localization and frictional strength of fault gouge through the use of a coupled 2-phase (pore fluid-grain) Finite Difference-Discrete Element Numerical model. The model simulates slip at earthquake velocities (~1m/s) in a fluid saturated gouge-filled fault. We find three types of shear behavior: (I) distributed shear, (II) random internal localization, and (III) boundary localization. Each shear type is dependent on the applied shear velocity, V, effective confining stress, N, and internal permeability, k. Through quantitative analysis of the positions and magnitude of localized shear bands, we show under which conditions the presence of and transitions between these shear types will occur. During shear, fluid pressure deviations, delta P, are generated by dilation and compaction cycles. The fluid effects on the system are more pronounced in simulations with higher V and lower N and k. Relative to the dry experiments, fluid saturated systems have an increased localization toward the boundaries of the gouge layer (type III), and no occurrence of distributed (type I) shear.
Systems with lower N and k show liquefaction events. Liquefaction events originate from increases in fluid pressure, delta P, around force chains between grains. Once delta P, the high pressures weaken the frictional forces between grains and destroy force chains. Shear then occurs at essentially zero friction until a new grain configuration recreates force chains. A reduction in mean friction is seen for systems with large liquefaction events (without inclusion of thermal pressurization), which could introduce a new mechanism in low friction faults. We also find that systems undergoing different types of shear will all trend toward type (III) shear following a liquefaction event.
Advisors/Committee Members: Sparks, David W (advisor).
Subjects/Keywords: geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Bianco, R. (2013). The Effects of Fluid Flow On Shear Localization and Frictional Strength From Dynamic Models Of Fault Gouge During Earthquakes. (Thesis). Texas Digital Library. Retrieved from http://hdl.handle.net/1969; http://hdl.handle.net/2249.1/66720
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Bianco, Ronald. “The Effects of Fluid Flow On Shear Localization and Frictional Strength From Dynamic Models Of Fault Gouge During Earthquakes.” 2013. Thesis, Texas Digital Library. Accessed April 23, 2018.
http://hdl.handle.net/1969; http://hdl.handle.net/2249.1/66720.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Bianco, Ronald. “The Effects of Fluid Flow On Shear Localization and Frictional Strength From Dynamic Models Of Fault Gouge During Earthquakes.” 2013. Web. 23 Apr 2018.
Vancouver:
Bianco R. The Effects of Fluid Flow On Shear Localization and Frictional Strength From Dynamic Models Of Fault Gouge During Earthquakes. [Internet] [Thesis]. Texas Digital Library; 2013. [cited 2018 Apr 23].
Available from: http://hdl.handle.net/1969; http://hdl.handle.net/2249.1/66720.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Bianco R. The Effects of Fluid Flow On Shear Localization and Frictional Strength From Dynamic Models Of Fault Gouge During Earthquakes. [Thesis]. Texas Digital Library; 2013. Available from: http://hdl.handle.net/1969; http://hdl.handle.net/2249.1/66720
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
23.
Baker, Benjamin Ian.
2.5d teleseismic waveform tomography with application to the tien shan.
Degree: 2014, Rensselaer Polytechnic Institute
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=3613267
► The analysis of passive source seismic data recorded by quasi-linear deployments of broadband stations at teleseismic distances has proven to be an effective means…
(more)
▼ The analysis of passive source seismic data recorded by quasi-linear deployments of broadband stations at teleseismic distances has proven to be an effective means of probing the subsurface of the Earth. However, current methodologies are far from being able to exploit all the interpretable signal in these data sets. In this thesis, I describe a 2.5D, frequency domain, visco-elastic waveform tomography algorithm for imaging with this type of data. To compute synthetic seismograms (the forward problem), the general equations of motion are discretized with p-adaptive finite elements. This approach allows for geometric flexibility and accurate solutions as a function of wavelength. Artificial force distributions manifesting Huygen's principle for the teleseismic events are introduced locally through a Bielak layer. Because of the relatively low frequency content of teleseismic data, regional scale tectonic settings can be parameterized with a modest number of variables and perturbations can be determined directly from a regularized Gauss-Newton system of equations. Waveforms generated by the forward problem compare well with analytic solutions for simple 1D media and with those generated in heterogeneous structures by a finite difference technique. It is demonstrated through examples that the regularized approximate Hessian is particularly effective at focusing backpropagated residuals to their true location. It is observed that full waveform inversion can provide significantly better vertical resolution than arrival time tomography and significantly better lateral resolution than standard surface wave tomography. Used in tandem in a multi-scale approach, surface wave tomography followed by joint surface wave/body wave tomography is shown to be an effective strategy for image reconstruction from a simple starting model. This inversion strategy is then applied to body and surface wave teleseismic waves recorded in the Tien Shan. The work of previous investigators is both corroborated and better illuminated by starting from a 1D model and inverting with this joint multi-scale approach. The main results for this application are (1) that the Tarim basin appears to be underthrusting the Tien Shan from the south, (2) a thin crust overlaying a piece of suspected relict lithosphere exists below the Naryn valley, and (3) there is a south dipping high velocity zone on the north side of the Tien Shan suggesting consumption of the Chu depression and the Kazak shield. The north dipping high velocity feature in the south and south dipping high velocity feature in the north are consistent with the hypothesis of dual subduction beneath the Tien Shan.
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Baker, B. I. (2014). 2.5d teleseismic waveform tomography with application to the tien shan. (Thesis). Rensselaer Polytechnic Institute. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=3613267
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Baker, Benjamin Ian. “2.5d teleseismic waveform tomography with application to the tien shan.” 2014. Thesis, Rensselaer Polytechnic Institute. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=3613267.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Baker, Benjamin Ian. “2.5d teleseismic waveform tomography with application to the tien shan.” 2014. Web. 23 Apr 2018.
Vancouver:
Baker BI. 2.5d teleseismic waveform tomography with application to the tien shan. [Internet] [Thesis]. Rensselaer Polytechnic Institute; 2014. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3613267.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Baker BI. 2.5d teleseismic waveform tomography with application to the tien shan. [Thesis]. Rensselaer Polytechnic Institute; 2014. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=3613267
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Colorado School of Mines
24.
Kamath, Nishant.
Full-waveform inversion in 2D VTI media.
Degree: 2016, Colorado School of Mines
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=10116167
► Full-waveform inversion (FWI) is a technique designed to produce a high-resolution model of the subsurface by using information contained in entire seismic waveforms. This…
(more)
▼ Full-waveform inversion (FWI) is a technique designed to produce a high-resolution model of the subsurface by using information contained in entire seismic waveforms. This thesis presents a methodology for FWI in elastic VTI (transversely isotropic with a vertical axis of symmetry) media and discusses synthetic results for heterogeneous VTI models. First, I develop FWI for multicomponent data from a horizontally layered VTI model. The reflectivity method, which permits computation of only PP reflections or a combination of PP and PSV events, is employed to model the data. The Gauss-Newton technique is used to invert for the interval Thomsen parameters, while keeping the densities fixed at the correct values. Eigenvalue/eigenvector decompostion of the Hessian matrix helps analyze the sensitivity of the objective function to the model parameters. Whereas PP data alone are generally sufficient to constrain all four Thomsen parameters even for conventional spreads, including PS reflections provides better constraints, especially for the deeper part of the model. Next, I derive the gradients of the FWI objective function with respect to the stiffness coefficients of arbitrarily anisotropic media by employing the adjoint-state method. From these expressions, it is straightforward to compute the gradients for parameters of 2D heterogeneous VTI media. FWI is implemented in the time domain with the steepest-descent method used to iteratively update the model. The algorithm is tested on transmitted multicomponent data generated for Gaussian anomalies in Thomsen parameters embedded in homogeneous VTI media. To test the sensitivity of the objective function to different model parameters, I derive an an- alytic expression for the Fréchet kernel of FWI for arbitrary anisotropic symmetry by using the Born approximation and asymptotic Green’s functions. The amplitude of the kernel, which represents the radiation pattern of a secondary source (that source describes a perturbation in a model parameter), yields the angle-dependent energy scattered by the perturbation. Then the radiation patterns are obtained for anomalies in VTI parameters embedded in isotropic homogeneous media and employed to analyze the inversion results for the transmission FWI experiments. To understand some of the challenges posed by data recorded in surface surveys, I generate the multicomponent wavefield for a model based on a geologic section of the Valhall Field in the North Sea. A multiscale approach is adopted to perform FWI in the time domain. For the available offset range, diving-wave energy illuminates the top 1.5 km of the section, with the updates in the deeper regions due primarily to the reflections. FWI is tested for three model parameterizations and the results are explained in terms of the P- and SV-radiation patterns described above. These parameterizations lead to different trade-offs, and the choice of parameterization for a given data set depends on the recorded offset range, the…
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Kamath, N. (2016). Full-waveform inversion in 2D VTI media. (Thesis). Colorado School of Mines. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=10116167
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Kamath, Nishant. “Full-waveform inversion in 2D VTI media.” 2016. Thesis, Colorado School of Mines. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=10116167.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Kamath, Nishant. “Full-waveform inversion in 2D VTI media.” 2016. Web. 23 Apr 2018.
Vancouver:
Kamath N. Full-waveform inversion in 2D VTI media. [Internet] [Thesis]. Colorado School of Mines; 2016. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=10116167.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Kamath N. Full-waveform inversion in 2D VTI media. [Thesis]. Colorado School of Mines; 2016. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=10116167
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Colorado School of Mines
25.
Singh, Satyan.
An inverse scattering approach to imaging using Marchenko equations in the presence of a free surface.
Degree: 2016, Colorado School of Mines
URL: http://pqdtopen.proquest.com/#viewpdf?dispub=10125227
► The Green's function is the impulse response of a system and is used to infer the properties of the system from surface measurements. In…
(more)
▼ The Green's function is the impulse response of a system and is used to infer the properties of the system from surface measurements. In exploration seismology, imaging algorithms use estimates of the Green's functions along with surface measurements to image the subsurface, i.e. locate the Earth's interfaces and its properties, so as to identify valuable energy resources. These conventional imaging algorithms only account for singly reflected waves (primaries) in the subsurface and hence, in the subsurface image, produce false interfaces in the presence of multiply reflected waves (internal and free-surface multiples). Recent work has shown that we can retrieve the Green's function that accounts for primaries and internal multiples. Imaging with these Green's functions reduces the artifacts caused by internal multiples compared to conventional imaging algorithms. These Green's functions require the free-surface multiples to be removed from the surface measurements before retrieval and imaging. I modify the retrieval of the Green's function to account for free-surface reflections and therefore no longer require the free-surface multiples to be removed from the surface measurements. Thus the Green's function, in the method I propose, includes not only primaries and internal multiples but also free-surface multiples. These Green's functions are constructed from an arbitrary point <i>in the subsurface</i> (no physical receiver is required at this location) to <i>the surface.</i> The method I use to retrieve the Green's function does not specify the approach to image the subsurface. In this thesis I also analyze different imaging strategies using the retrieved Green's functions. Imaging with these Green's functions reduces the artifacts caused by multiply reflected waves compared to standard imaging algorithms. Significantly, the Green's function that I retrieve and use for imaging require the same inputs as conventional imaging algorithms: the surface measurements and a smooth version of the subsurface velocity. I also extend the construction of the Green's function from the subsurface to the surface to any two arbitrary points in the <i>subsurface</i> (no physical source or physical receiver is required at either of these locations). This Green's function is called the virtual Green's function and includes all the primaries, internal and free-surface multiples. The virtual Green's function retrieval requires the same inputs as the previously mentioned Green's functions.
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Singh, S. (2016). An inverse scattering approach to imaging using Marchenko equations in the presence of a free surface. (Thesis). Colorado School of Mines. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=10125227
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Singh, Satyan. “An inverse scattering approach to imaging using Marchenko equations in the presence of a free surface.” 2016. Thesis, Colorado School of Mines. Accessed April 23, 2018.
http://pqdtopen.proquest.com/#viewpdf?dispub=10125227.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Singh, Satyan. “An inverse scattering approach to imaging using Marchenko equations in the presence of a free surface.” 2016. Web. 23 Apr 2018.
Vancouver:
Singh S. An inverse scattering approach to imaging using Marchenko equations in the presence of a free surface. [Internet] [Thesis]. Colorado School of Mines; 2016. [cited 2018 Apr 23].
Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=10125227.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Singh S. An inverse scattering approach to imaging using Marchenko equations in the presence of a free surface. [Thesis]. Colorado School of Mines; 2016. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=10125227
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Duke University
26.
Kahn, Dan Scott.
Hydro-Fractured Reservoirs: a Study Using Double-Difference Location Techniques.
Degree: 2008, Duke University
URL: http://hdl.handle.net/10161/646
► The mapping of induced seismicity in enhanced geothermal systems presents the best tool available for understanding the resulting hydro-fractured reservoir. In this thesis, two…
(more)
▼ The mapping of induced seismicity in enhanced geothermal systems presents the best tool available for understanding the resulting hydro-fractured reservoir. In this thesis, two geothermal systems are studied; one in Krafla, Iceland and the other in Basel Switzerland. The purpose of the Krafla survey was to determine the relation between water injection into the fault system and the resulting earthquakes and fluid pressure in the subsurface crack system. The epicenters obtained from analyzing the seismic data gave a set of locations that are aligned along the border of a high resistivity zone ~2500 meters below the injection well. Further magneto-telluric/seismic-data correlation was seen in the polarity of the cracks through shear wave splitting. The purpose of the Basel project was to examine the creation of a reservoir by the initial stimulation, using an injection well bored to 5000 meters. This stimulation triggered a M3.4 event, extending the normal range of event sizes commonly incurred in hydro-fractured reservoirs. To monitor the seismic activity 6 seismometer sondes were deployed at depths from 317 to 2740 meters below the ground surface. During the seven-day period over 13,000 events were recorded and approximately 3,300 located. These events were first located by single-difference techniques. Subsequently, after calculating their cross-correlation coefficients, clusters of events were relocated using a double-difference algorithm. The event locations support the existence of a narrow reservoir spreading form the injection well. Analysis of the seismic data indicates that the reservoir grew at a uniform rate punctuated by fluctuations which occurred at times of larger events, which were perhaps caused by sudden changes in pressure. The orientation and size of the main fracture plane was found by determining focal mechanisms and locating events that were similar to the M3.4 event. To address the question of whether smaller quakes are simply larger quakes scaled down, the data set was analyzed to determine whether scaling relations held for the source parameters, including seismic moment, source dimension, stress drop, radiated energy and apparent stress. It was found that there was a breakdown in scaling for smaller quakes.
Advisors/Committee Members: Pratson, Lincoln (advisor), Malin, Peter (advisor).
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Kahn, D. S. (2008). Hydro-Fractured Reservoirs: a Study Using Double-Difference Location Techniques. (Thesis). Duke University. Retrieved from http://hdl.handle.net/10161/646
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Kahn, Dan Scott. “Hydro-Fractured Reservoirs: a Study Using Double-Difference Location Techniques.” 2008. Thesis, Duke University. Accessed April 23, 2018.
http://hdl.handle.net/10161/646.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Kahn, Dan Scott. “Hydro-Fractured Reservoirs: a Study Using Double-Difference Location Techniques.” 2008. Web. 23 Apr 2018.
Vancouver:
Kahn DS. Hydro-Fractured Reservoirs: a Study Using Double-Difference Location Techniques. [Internet] [Thesis]. Duke University; 2008. [cited 2018 Apr 23].
Available from: http://hdl.handle.net/10161/646.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Kahn DS. Hydro-Fractured Reservoirs: a Study Using Double-Difference Location Techniques. [Thesis]. Duke University; 2008. Available from: http://hdl.handle.net/10161/646
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Columbia University
27.
Block, Adrienne.
Geophysical perspectives of subglacial settings and their
influence on glacial dynamics.
Degree: PhD, Earth and Environmental SciencesLamont-Doherty Earth
Observatory, 2011, Columbia University
URL: https://academiccommons.columbia.edu/catalog/ac:187337
%%%
doi:10.7916/D8F47NBF
► The subglacial settings of glaciers and continental ice sheets serve as a fundamental, long term control on the dynamics of the ice but are also…
(more)
▼ The subglacial settings of glaciers and continental
ice sheets serve as a fundamental, long term control on the
dynamics of the ice but are also obscured by the great thickness of
the ice. Integrated analysis of geophysical datasets is a
fundamental tool for understanding a glacier's underpinnings. Using
a combination of gravity, magnetic, radar and surface elevation
data, we examine the relationship between the ice and its
subglacial setting in three chapters that address the question on
varying scales. The first explores the Gamburtsev Subglacial
Mountains, a region of high topography in the center of East
Antarctica. This range is thought to be the nucleation site of the
East Antarctic Ice Sheet despite the lack of evidence to constrain
its age. The geophysical data suggest a crustal architecture which,
when compared with global mountain ranges, provides insight to the
age and origin of the Gamburtsev Subglacial Mountains. We conclude
that the mountains are over crust that was thickened in the
Precambrian but have been been reactivated, creating their high
modern relief. In the second chapter, we explore the Recovery Ice
Stream in East Antarctica. Here the onset of fast flow is more than
500 km in the ice sheet interior and is thought to be linked to
periodic drainages from four large Recovery Lakes. Using new
aerogeophysical data in the region, we uncover two tectonic
boundaries that each play a key role in the dynamics of the ice
stream. The inland boundary limits the catchment of the lakes and
their potential for frequent flood events. The second boundary is a
transition from rugged bedrock to smooth, low-lying sediments. We
conclude that the basal sediments facilitate fast flow independent
of water input from the large Recovery Lakes. In the third and
final chapter, we examine Jakobshavn Isbrae, West Greenland, the
fastest moving non-surge glacier. Since the loss of its floating
ice tongue beginning in 1998, this glacier has accelerated and now
maintains fast flow speeds throughout the year. The glacier has a
known subglacial trough and high driving stresses but even these
optimal conditions cannot explain the late summer velocities. We
find that the geophysical signals in the Jakobshavn Isbrae region
require more geophysical contrasts than the coastal outcrops
suggest. Specifically, we interpret a trough-centered gravity low
as evidence of sediments underlying the radar-detected trough.
These sediments facilitate fast flow by reducing basal resistance.
Though Jakobshavn Isbrae is a glaciological endmember, its fate is
linked to the underlying geology and best demonstrates the need for
continued aerogeophysical survey to constrain subglacial settings.
Understanding conditions at the bed is fundamental to understanding
the state and fate of the planet's ice.
Advisors/Committee Members: Bell, Robin E. (Advisor).
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Block, A. (2011). Geophysical perspectives of subglacial settings and their
influence on glacial dynamics. (Doctoral Dissertation). Columbia University. Retrieved from https://academiccommons.columbia.edu/catalog/ac:187337 %%% doi:10.7916/D8F47NBF
Chicago Manual of Style (16th Edition):
Block, Adrienne. “Geophysical perspectives of subglacial settings and their
influence on glacial dynamics.” 2011. Doctoral Dissertation, Columbia University. Accessed April 23, 2018.
https://academiccommons.columbia.edu/catalog/ac:187337 %%% doi:10.7916/D8F47NBF.
MLA Handbook (7th Edition):
Block, Adrienne. “Geophysical perspectives of subglacial settings and their
influence on glacial dynamics.” 2011. Web. 23 Apr 2018.
Vancouver:
Block A. Geophysical perspectives of subglacial settings and their
influence on glacial dynamics. [Internet] [Doctoral dissertation]. Columbia University; 2011. [cited 2018 Apr 23].
Available from: https://academiccommons.columbia.edu/catalog/ac:187337 %%% doi:10.7916/D8F47NBF.
Council of Science Editors:
Block A. Geophysical perspectives of subglacial settings and their
influence on glacial dynamics. [Doctoral Dissertation]. Columbia University; 2011. Available from: https://academiccommons.columbia.edu/catalog/ac:187337 %%% doi:10.7916/D8F47NBF
Columbia University
28.
Foster, Anna.
Surface-wave propagation and phase-velocity structure from
observations on the USArray Transportable Array.
Degree: PhD, Earth and Environmental Sciences, 2014, Columbia University
URL: https://academiccommons.columbia.edu/catalog/ac:175906
%%%
doi:10.7916/D8959FQR
► We address questions relating to the velocity structure of the Earth in three ways: mapping the phase-velocity structure of the western United States, examining deviations…
(more)
▼ We address questions relating to the velocity
structure of the Earth in three ways: mapping the phase-velocity
structure of the western United States, examining deviations of
wave paths due to lateral variations in velocity, and demonstrating
that Love wave fundamental-mode phase measurements from array
methods can be significantly contaminated by overtone interference,
dependent on differences in fundamental-mode and first-overtone
phase-velocity structure. All of the studies presented in this work
use USArray Transportable Array data, which allow for dense,
high-quality measurements at an unprecedented level.
Advisors/Committee Members: Ekstrom, Goran (Advisor).
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Foster, A. (2014). Surface-wave propagation and phase-velocity structure from
observations on the USArray Transportable Array. (Doctoral Dissertation). Columbia University. Retrieved from https://academiccommons.columbia.edu/catalog/ac:175906 %%% doi:10.7916/D8959FQR
Chicago Manual of Style (16th Edition):
Foster, Anna. “Surface-wave propagation and phase-velocity structure from
observations on the USArray Transportable Array.” 2014. Doctoral Dissertation, Columbia University. Accessed April 23, 2018.
https://academiccommons.columbia.edu/catalog/ac:175906 %%% doi:10.7916/D8959FQR.
MLA Handbook (7th Edition):
Foster, Anna. “Surface-wave propagation and phase-velocity structure from
observations on the USArray Transportable Array.” 2014. Web. 23 Apr 2018.
Vancouver:
Foster A. Surface-wave propagation and phase-velocity structure from
observations on the USArray Transportable Array. [Internet] [Doctoral dissertation]. Columbia University; 2014. [cited 2018 Apr 23].
Available from: https://academiccommons.columbia.edu/catalog/ac:175906 %%% doi:10.7916/D8959FQR.
Council of Science Editors:
Foster A. Surface-wave propagation and phase-velocity structure from
observations on the USArray Transportable Array. [Doctoral Dissertation]. Columbia University; 2014. Available from: https://academiccommons.columbia.edu/catalog/ac:175906 %%% doi:10.7916/D8959FQR
Columbia University
29.
Jia, Tianxia.
Advanced analysis of complex seismic waveforms to
characterize the subsurface Earth structure.
Degree: PhD, Earth and Environmental SciencesLamont-Doherty Earth
Observatory, 2011, Columbia University
URL: https://academiccommons.columbia.edu/catalog/ac:137451
%%%
handle:10022/AC
► This thesis includes three major parts, (1) Body wave analysis of mantle structure under the Calabria slab, (2) Spatial Average Coherency (SPAC) analysis of microtremor…
(more)
▼ This thesis includes three major parts, (1) Body wave
analysis of mantle structure under the Calabria slab, (2) Spatial
Average Coherency (SPAC) analysis of microtremor to characterize
the subsurface structure in urban areas, and (3) Surface wave
dispersion inversion for shear wave velocity structure. Although
these three projects apply different techniques and investigate
different parts of the Earth, their aims are the same, which is to
better understand and characterize the subsurface Earth structure
by analyzing complex seismic waveforms that are recorded on the
Earth surface. My first project is body wave analysis of mantle
structure under the Calabria slab. Its aim is to better understand
the subduction structure of the Calabria slab by analyzing
seismograms generated by natural earthquakes. The rollback and
subduction of the Calabrian Arc beneath the southern Tyrrhenian Sea
is a case study of slab morphology and slab-mantle interactions at
short spatial scale. I analyzed the seismograms traversing the
Calabrian slab and upper mantle wedge under the southern Tyrrhenian
Sea through body wave dispersion, scattering and attenuation, which
are recorded during the PASSCAL CAT/SCAN experiment. Compressional
body waves exhibit dispersion correlating with slab paths, which is
high-frequency components arrivals being delayed relative to
low-frequency components. Body wave scattering and attenuation are
also spatially correlated with slab paths. I used this correlation
to estimate the positions of slab boundaries, and further suggested
that the observed spatial variation in near-slab attenuation could
be ascribed to mantle flow patterns around the slab. My second
project is Spatial Average Coherency (SPAC) analysis of
microtremors for subsurface structure characterization. Shear-wave
velocity (Vs) information in soil and rock has been recognized as a
critical parameter for site-specific ground motion prediction
study, which is highly necessary for urban areas located in seismic
active zones. SPAC analysis of microtremors provides an efficient
way to estimate Vs structure. Compared with other Vs estimating
methods, SPAC is noninvasive and does not require any active
sources, and therefore, it is especially useful in big cities. I
applied SPAC method in two urban areas. The first is the historic
city, Charleston, South Carolina, where high levels of seismic
hazard lead to great public concern. Accurate Vs information,
therefore, is critical for seismic site classification and site
response studies. The second SPAC study is in Manhattan, New York
City, where depths of high velocity contrast and soil-to-bedrock
are different along the island. The two experiments show that Vs
structure could be estimated with good accuracy using SPAC method
compared with borehole and other techniques. SPAC is proved to be
an effective technique for Vs estimation in urban areas. One
important issue in seismology is the inversion of subsurface
structures from surface recordings of seismograms. My third project
focuses on solving this complex…
Advisors/Committee Members: Lerner-Lam, Arthur L. (Advisor).
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Jia, T. (2011). Advanced analysis of complex seismic waveforms to
characterize the subsurface Earth structure. (Doctoral Dissertation). Columbia University. Retrieved from https://academiccommons.columbia.edu/catalog/ac:137451 %%% handle:10022/AC
Chicago Manual of Style (16th Edition):
Jia, Tianxia. “Advanced analysis of complex seismic waveforms to
characterize the subsurface Earth structure.” 2011. Doctoral Dissertation, Columbia University. Accessed April 23, 2018.
https://academiccommons.columbia.edu/catalog/ac:137451 %%% handle:10022/AC.
MLA Handbook (7th Edition):
Jia, Tianxia. “Advanced analysis of complex seismic waveforms to
characterize the subsurface Earth structure.” 2011. Web. 23 Apr 2018.
Vancouver:
Jia T. Advanced analysis of complex seismic waveforms to
characterize the subsurface Earth structure. [Internet] [Doctoral dissertation]. Columbia University; 2011. [cited 2018 Apr 23].
Available from: https://academiccommons.columbia.edu/catalog/ac:137451 %%% handle:10022/AC.
Council of Science Editors:
Jia T. Advanced analysis of complex seismic waveforms to
characterize the subsurface Earth structure. [Doctoral Dissertation]. Columbia University; 2011. Available from: https://academiccommons.columbia.edu/catalog/ac:137451 %%% handle:10022/AC
Columbia University
30.
Han, Shuoshuo.
Accretion and Subduction of Oceanic Lithosphere: 2D and 3D
Seismic Studies of Off-Axis Magma Lenses at East Pacific Rise
9°37-40'N Area...
Degree: PhD, Earth and Environmental Sciences, 2015, Columbia University
URL: https://academiccommons.columbia.edu/catalog/ac:184190
%%%
doi:10.7916/D80000ZK
► Two thirds of the Earth's lithosphere is covered by the ocean. The oceanic lithosphere is formed at mid-ocean ridges, evolves and interacts with the overlying…
(more)
▼ Two thirds of the Earth's lithosphere is covered by
the ocean. The oceanic lithosphere is formed at mid-ocean ridges,
evolves and interacts with the overlying ocean for millions of
years, and is eventually consumed at subduction zones. In this
thesis, I use 2D and 3D multichannel seismic (MCS) data to
investigate the accretionary and hydrothermal process on the ridge
flank of the fast-spreading East Pacific Rise (EPR) at 9°37-40'N
and the structure of the downgoing Juan de Fuca plate at the
Cascadia subduction zone offshore Oregon and
Washington.
Advisors/Committee Members: Carbotte, Suzanne M. (Advisor).
Subjects/Keywords: Geophysics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Han, S. (2015). Accretion and Subduction of Oceanic Lithosphere: 2D and 3D
Seismic Studies of Off-Axis Magma Lenses at East Pacific Rise
9°37-40'N Area... (Doctoral Dissertation). Columbia University. Retrieved from https://academiccommons.columbia.edu/catalog/ac:184190 %%% doi:10.7916/D80000ZK
Chicago Manual of Style (16th Edition):
Han, Shuoshuo. “Accretion and Subduction of Oceanic Lithosphere: 2D and 3D
Seismic Studies of Off-Axis Magma Lenses at East Pacific Rise
9°37-40'N Area...” 2015. Doctoral Dissertation, Columbia University. Accessed April 23, 2018.
https://academiccommons.columbia.edu/catalog/ac:184190 %%% doi:10.7916/D80000ZK.
MLA Handbook (7th Edition):
Han, Shuoshuo. “Accretion and Subduction of Oceanic Lithosphere: 2D and 3D
Seismic Studies of Off-Axis Magma Lenses at East Pacific Rise
9°37-40'N Area...” 2015. Web. 23 Apr 2018.
Vancouver:
Han S. Accretion and Subduction of Oceanic Lithosphere: 2D and 3D
Seismic Studies of Off-Axis Magma Lenses at East Pacific Rise
9°37-40'N Area... [Internet] [Doctoral dissertation]. Columbia University; 2015. [cited 2018 Apr 23].
Available from: https://academiccommons.columbia.edu/catalog/ac:184190 %%% doi:10.7916/D80000ZK.
Council of Science Editors:
Han S. Accretion and Subduction of Oceanic Lithosphere: 2D and 3D
Seismic Studies of Off-Axis Magma Lenses at East Pacific Rise
9°37-40'N Area... [Doctoral Dissertation]. Columbia University; 2015. Available from: https://academiccommons.columbia.edu/catalog/ac:184190 %%% doi:10.7916/D80000ZK
◁ [1] [2] [3] [4] [5] … [104] ▶
. 
Open Access Theses and Dissertations