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1. WANG, Yun. Seismic Tomography in the Crust and Upper Mantle of the Gulf of California Region.

Degree: PhD, Geological Sciences, 2012, Brown University

The primary goal of this thesis is to image 3-D seismic velocity anomalies in the crust and upper mantle of the Gulf of California region, and then translate the velocity anomalies to variations in temperature and composition and then dynamics in the Earth’s interior. We constructed a moderate-resolution 3-D velocity model employing an array-processing method, which describes the incoming wave field as the interference of two plane waves that travel along slightly different direction from the great circle paths and applied 2-D finite frequency kernels to represent surface wave scattering within the study area. Tomography results show two pronounced features. First, there are low shear velocities similar to those beneath the East Pacific Rise oceanic spreading center underlie the entire length of the Gulf, but there are three concentrated locations of anomalously low velocities spaced about 250 kilometers apart. We interpret these seismic velocity anomalies as indicating that partial melting triggers dynamic upwelling driven by either the buoyancy of retained melt or by the reduced density of depleted mantle. Second, there are high velocity anomalies landward of the Guadalupe and Magdalena microplates, which we interpreted as undetached fossil slabs. Meanwhile, a conjunction tomography study of surface wave and body wave in the southwestern US showed high velocity anomaly landward of the Monterrey microplate, well known as Isabella anomaly, which has previously been interpreted as a lithospheric drip or attributed to delamination of the Sierra Nevada lithospheric root. Here we reinterpreted the anomaly as fossil slabs attached to the unsubducted Monterey microplates. A combination of tomographic results in the Baja California and southwestern US allows us to address the fate of fossil slab fragments attached to the unsubducted Farallon plate. The Guadalupe/Magdalena fossil slab extends to a depth of 130+ km, while the Monterey microplate may extend deeper than 200 km. With such an accurate moderate-resolution 3-D velocity model to start with and well-constrained source parameters for regional events, we are able to carry on a high-resolution tomography study using SEM and adjoint method in the future. Advisors/Committee Members: Forsyth, Donald (Director), Fischer, Karen (Reader), Parmentier, Marc (Reader), Liang, Yan (Reader), Savage, Brian (Reader).

Subjects/Keywords: Gulf of California

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

APA (6th Edition):

WANG, Y. (2012). Seismic Tomography in the Crust and Upper Mantle of the Gulf of California Region. (Doctoral Dissertation). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:297649/

Chicago Manual of Style (16th Edition):

WANG, Yun. “Seismic Tomography in the Crust and Upper Mantle of the Gulf of California Region.” 2012. Doctoral Dissertation, Brown University. Accessed December 10, 2019. https://repository.library.brown.edu/studio/item/bdr:297649/.

MLA Handbook (7th Edition):

WANG, Yun. “Seismic Tomography in the Crust and Upper Mantle of the Gulf of California Region.” 2012. Web. 10 Dec 2019.

Vancouver:

WANG Y. Seismic Tomography in the Crust and Upper Mantle of the Gulf of California Region. [Internet] [Doctoral dissertation]. Brown University; 2012. [cited 2019 Dec 10]. Available from: https://repository.library.brown.edu/studio/item/bdr:297649/.

Council of Science Editors:

WANG Y. Seismic Tomography in the Crust and Upper Mantle of the Gulf of California Region. [Doctoral Dissertation]. Brown University; 2012. Available from: https://repository.library.brown.edu/studio/item/bdr:297649/

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