subject:(icequakes)

Penn State University

1. Pourpoint, Maeva. LITHOSPHERIC AND GLACIAL STRUCTURES FROM SEISMIC WAVE ANALYSIS IN GREENLAND AND ANTARCTICA.

Degree: 2018, Penn State University

URL: https://submit-etda.libraries.psu.edu/catalog/15540mup23

► The mass balance of ice sheets is controlled by the dynamics of ice streams and glaciers which are in turn influenced by underlying geologic and… (more)

▼ The mass balance of ice sheets is controlled by the dynamics of ice streams and glaciers which are in turn influenced by underlying geologic and geophysical processes. In this thesis, I use passive seismic measurements to improve constraints on glacial and lithospheric structures and to monitor temporal and spatial changes in glacier dynamic processes. Chapters 2 and 3 focus on imaging the crustal and upper mantle velocity structure of Greenland and investigating how subsurface properties may impact the long-term ice- sheet stability. To circumvent the limitations of a sparse network in a region with limited seismicity and improve upon the resolution of previous regional surface wave tomography models, I develop a new seismic processing approach that takes advantage of azimuthally well-distributed teleseismic events and available global dispersion models in order to expand regional data coverage and build path-specific dispersion curves. This global correction approach results in an unprecedentedly high-resolution group velocity model of Greenland (Chapter 2). Building upon this model, I combine ambient noise and earthquake data to derive a 3-D shear wave velocity model of Greenland’s lithosphere from 10 to 200 km depth. Model uncertainties and robust model features are estimated by means of Bayesian inversion. The derived shear wave velocity model presents important structural details that correlate well with regional geologic features and shed light on the tectonic history of Greenland and its modern geologic environment (Chapter 3). Chapter 4 examines possible variations in Byrd glacier’s dynamics via analysis of ice seismicity recorded during a summer field season. The results of this study indicate that, similar to other outlet glaciers, seismicity upstream of Byrd glacier is tidally- modulated and that seismicity detected in Byrd’s catchment is most likely associated with internal deformation of the firn layer. In chapter 4, I also explore the potential to use high frequency ambient seismicity to image ice structure and find that conventional seismic interferometry approach can be used even in regions with low ambient seismic noise levels which could have some positive implications for continuous seismic monitoring of subsurface structures at non-tidewater and dry polar glaciers. Advisors/Committee Members: Sridhar Anandakrishnan, Dissertation Advisor/Co-Advisor, Sridhar Anandakrishnan, Committee Chair/Co-Chair, Charles A. Ammon, Committee Member, Richard B. Alley, Committee Member, Parisa Shokouki, Outside Member.

Subjects/Keywords: Surface wave tomography; Greenland; Icequakes; Byrd glacier; Antarctica

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Pourpoint, M. (2018). LITHOSPHERIC AND GLACIAL STRUCTURES FROM SEISMIC WAVE ANALYSIS IN GREENLAND AND ANTARCTICA. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/15540mup23

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Pourpoint, Maeva. “LITHOSPHERIC AND GLACIAL STRUCTURES FROM SEISMIC WAVE ANALYSIS IN GREENLAND AND ANTARCTICA.” 2018. Thesis, Penn State University. Accessed April 12, 2021. https://submit-etda.libraries.psu.edu/catalog/15540mup23.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Pourpoint, Maeva. “LITHOSPHERIC AND GLACIAL STRUCTURES FROM SEISMIC WAVE ANALYSIS IN GREENLAND AND ANTARCTICA.” 2018. Web. 12 Apr 2021.

Vancouver:

Pourpoint M. LITHOSPHERIC AND GLACIAL STRUCTURES FROM SEISMIC WAVE ANALYSIS IN GREENLAND AND ANTARCTICA. [Internet] [Thesis]. Penn State University; 2018. [cited 2021 Apr 12]. Available from: https://submit-etda.libraries.psu.edu/catalog/15540mup23.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Pourpoint M. LITHOSPHERIC AND GLACIAL STRUCTURES FROM SEISMIC WAVE ANALYSIS IN GREENLAND AND ANTARCTICA. [Thesis]. Penn State University; 2018. Available from: https://submit-etda.libraries.psu.edu/catalog/15540mup23

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

2. Cooley, Jade. Tidal and Structural Controls on Seismic Events Near the Grounding Line at Beardmore Glacier, Antarctica.

Degree: MS, Geological Sciences, 2017, Central Washington University

URL: https://digitalcommons.cwu.edu/etd/700

► Here I report seismic events occurring over a three-week period during the 2013-2014 austral summer near the grounding line of Beardmore Glacier, Antarctica. The ~24000… (more)

Subjects/Keywords: cryoseismology; Ross Ice Shelf; icequakes; buttressing; GPS; Geophysics and Seismology; Glaciology

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Cooley, J. (2017). Tidal and Structural Controls on Seismic Events Near the Grounding Line at Beardmore Glacier, Antarctica. (Masters Thesis). Central Washington University. Retrieved from https://digitalcommons.cwu.edu/etd/700

Chicago Manual of Style (16^th Edition):

Cooley, Jade. “Tidal and Structural Controls on Seismic Events Near the Grounding Line at Beardmore Glacier, Antarctica.” 2017. Masters Thesis, Central Washington University. Accessed April 12, 2021. https://digitalcommons.cwu.edu/etd/700.

MLA Handbook (7^th Edition):

Cooley, Jade. “Tidal and Structural Controls on Seismic Events Near the Grounding Line at Beardmore Glacier, Antarctica.” 2017. Web. 12 Apr 2021.

Vancouver:

Cooley J. Tidal and Structural Controls on Seismic Events Near the Grounding Line at Beardmore Glacier, Antarctica. [Internet] [Masters thesis]. Central Washington University; 2017. [cited 2021 Apr 12]. Available from: https://digitalcommons.cwu.edu/etd/700.

Council of Science Editors:

Cooley J. Tidal and Structural Controls on Seismic Events Near the Grounding Line at Beardmore Glacier, Antarctica. [Masters Thesis]. Central Washington University; 2017. Available from: https://digitalcommons.cwu.edu/etd/700

Colorado State University

3. Cole, Hank M. Tidally induced seismicity at the grounded margins of the Ross Ice Shelf, Antarctica.

Degree: MS(M.S.), Geosciences, 2020, Colorado State University

URL: http://hdl.handle.net/10217/212036

► Repeating swarms of local icequakes were recorded by broadband seismograpghs deployed near the grounding line of the Ross Ice Shelf, Antarctica from late 2014 to… (more)

▼ Repeating swarms of local icequakes were recorded by broadband seismograpghs deployed near the grounding line of the Ross Ice Shelf, Antarctica from late 2014 to early 2017. Swarms commonly persist for over six hours and contain thousands of events. Most swarms are induced or enhanced by tidal forcing. The number of events and event amplitudes in a swarm is most correlated with the modeled tide range. Some swarms only occur during cold periods of the austral winter. Icequakes are cataloged using a cross-correlation detector after building a template library from clustered STA/LTA picks and epicenters are estimated for high quality events. Events can be classified into four broad categories. The first event type is the most common (>95% of events) and occurs in diurnal swarms at all times of year. This type of event is interpreted to be sourced by propagation of near surface crevasses due to enhanced tensile stress from downward flexure of the ice shelf during falling tide. The second type of event has similar waveforms but occurs at the crest of large spring tides and appears to have an englacial or basal source. The third type of event is likely sourced from within the firn, possibly related to densification. It is also observed at stations in the ice shelf interior, but appears enhanced by tides at stations near the grounding line. The fourth type of event is only observed at a station on the Steershead Ice Rise. These are sweeping harmonic tremors lasting up to 8 s that start at low frequency and then tail upwards into an impulse like signal. This work characterizes these icequake types and their correlation to tidal and environmental forcing. It also details a single station event location scheme that is to used to further interpret events by finding their back azimuth with a polarization analysis and estimate their source-receiver distance with two methods. These observations provide insight into the deformation and brittle fracture at the grounded margins of the Ross Ice Shelf. Advisors/Committee Members: Aster, Richard C. (advisor), McGrath, Daniel (committee member), Cheney, Margaret (committee member), Benz, Harley (committee member).

Subjects/Keywords: grounding line; icequakes; tides; ice shelf; seismology; Antarctica

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Cole, H. M. (2020). Tidally induced seismicity at the grounded margins of the Ross Ice Shelf, Antarctica. (Masters Thesis). Colorado State University. Retrieved from http://hdl.handle.net/10217/212036

Chicago Manual of Style (16^th Edition):

Cole, Hank M. “Tidally induced seismicity at the grounded margins of the Ross Ice Shelf, Antarctica.” 2020. Masters Thesis, Colorado State University. Accessed April 12, 2021. http://hdl.handle.net/10217/212036.

MLA Handbook (7^th Edition):

Cole, Hank M. “Tidally induced seismicity at the grounded margins of the Ross Ice Shelf, Antarctica.” 2020. Web. 12 Apr 2021.

Vancouver:

Cole HM. Tidally induced seismicity at the grounded margins of the Ross Ice Shelf, Antarctica. [Internet] [Masters thesis]. Colorado State University; 2020. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/10217/212036.

Council of Science Editors:

Cole HM. Tidally induced seismicity at the grounded margins of the Ross Ice Shelf, Antarctica. [Masters Thesis]. Colorado State University; 2020. Available from: http://hdl.handle.net/10217/212036

4. Carmichael, Joshua D. Melt-Triggered Seismic Response in Hydraulically-Active Polar Ice: Observations and Methods.

Degree: PhD, 2014, University of Washington

URL: http://hdl.handle.net/1773/25007

► Glacier ice responds to environmental forcing through changes in its sliding speed and mass balance. While these changes often occur on daily time scales or… (more)

▼ Glacier ice responds to environmental forcing through changes in its sliding speed and mass balance. While these changes often occur on daily time scales or longer, they are initiated by brittle deformation events that establish hydrological pathways in hours or seconds and allow meltwater access to englacial or subglacial depths to facilitate ice motion. In this thesis, we (various contributing authors including myself) use seismic monitoring to detect and locate the creation and growth of some of these hydraulic pathways by monitoring their seismic emissions, or icequakes. More specifically, we address (1) what seismic observables, unavailable from other sensing methods, indicate an initial glaciogenic response to melt- water input and (2) if these comprise evidence of feedbacks that may destabilize polar ice under a warming climate. Supplemental to our scientific contributions, we advance statistical processing methods that demonstrably improve the capability of digital detectors at discriminating icequakes from astationary noise. We begin by interpreting geophysical observations collected from a dry-based, sub-freezing (-17 ^o C), polar glacier environment (Taylor Glacier, ANT). By implementing a calibrated surface energy balance model, we estimate the timing and volume of surface meltwater generated during the collection of seismic data from a six-receiver geophone network. This comparison illustrated that any effectively nonzero meltwater triggered large, repeating icequakes localized near a deep, supraglacial-to-subglacial crack within a melt-water catchment region. The focal mechanisms of these icequakes are consistent with an expansive growth within the crack. Their occurrence at night suggests that this expansion was accommodated by volumetric straining of confined, re-freezing meltwater. These cracks likely sustained their surface-to-bed hydrological connection, in the absence of melt-assisted basal sliding. Further, this appears to be the first report attributing seismogensis in glacial ice to fracturing induced by phase change. We proceed by contrasting these response characteristics with geophysical observations following an early (spring) supraglacial lake drainage within the lake-forming ablation zone of the Western Greenland Ice Sheet. The subglacial drainage system present during this time was considered incapable of efficiently draining large fluxes of meltwater input and therefore likely to undergo transient motion. Using measurements from a ~5km-aperture geophone network, we find that the anticipated post-drainage icequakes are diurnally responsive, largely surficial in origin, and indicative of tensile fracturing from shallow cracks in the ice. The creation of the lake-drainage moulin appears to coincide with a shift in mean icequake source locations, and an increase in icequake occurrence at night relative to that in the day. Contrary to our expectations, we find that the timing of GPS-derived surface speeds do not clearly indicate this seismic activity on any given day. Rather,… Advisors/Committee Members: Joughin, Ian R (advisor).

Subjects/Keywords: Glacial hydraulics; Glaciology; Icequakes; Seismic Monitoring; Signal Detection; Statistical Signal Processing; Geophysics; Electrical engineering; Statistics; earth and space sciences

…illustrated in Greenland. Here, deep local icequakes are likely muted by noise, waveform-attenuating… …6 1.4 Melt-Triggered Icequakes: Review and Need for Research . . . . . . . . . . . 9… …Threshold Detection of Basal Seismicity and Low-Frequency Icequakes… …Frequency Icequakes (LFIs) . . . . . . . . . . . . . . . . . . . . . . . . Possible… …Attenuation Operation Used to Locate Icequakes; Seismic Quality Factors 75 3.6 2011 Greenland…

10 more images…

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Carmichael, J. D. (2014). Melt-Triggered Seismic Response in Hydraulically-Active Polar Ice: Observations and Methods. (Doctoral Dissertation). University of Washington. Retrieved from http://hdl.handle.net/1773/25007

Chicago Manual of Style (16^th Edition):

Carmichael, Joshua D. “Melt-Triggered Seismic Response in Hydraulically-Active Polar Ice: Observations and Methods.” 2014. Doctoral Dissertation, University of Washington. Accessed April 12, 2021. http://hdl.handle.net/1773/25007.

MLA Handbook (7^th Edition):

Carmichael, Joshua D. “Melt-Triggered Seismic Response in Hydraulically-Active Polar Ice: Observations and Methods.” 2014. Web. 12 Apr 2021.

Vancouver:

Carmichael JD. Melt-Triggered Seismic Response in Hydraulically-Active Polar Ice: Observations and Methods. [Internet] [Doctoral dissertation]. University of Washington; 2014. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/1773/25007.

Council of Science Editors:

Carmichael JD. Melt-Triggered Seismic Response in Hydraulically-Active Polar Ice: Observations and Methods. [Doctoral Dissertation]. University of Washington; 2014. Available from: http://hdl.handle.net/1773/25007

		in
And / Or
		in
And / Or
		in
And / Or
		in

Open Access Theses and Dissertations