Doctoral Dissertations

Keywords and Phrases

Body wave; Computational seismology; Crust deformation; Mantle processes; Seismic anisotropy

Abstract

"Numerous geophysical studies suggest that seismic anisotropy is a nearly ubiquitous property of the Earth’s crust and upper mantle. In this study, we utilize the shear wave splitting technique to investigate the piercing-point-dependent azimuthal anisotropy beneath the northeastern edge of the Sichuan Basin in central China, and the spatial and temporal variations of anisotropy near the 2019 M7.1 Ridgecrest earthquake in California, respectively. A clear back azimuthal dependence of the splitting parameters and the lack of a 90° or 180° periodicity of azimuthal variation in the observed fast orientations provide strong evidence for the existence of piercing-point-dependent anisotropy beneath the Sichuan Basin. It is inferred that the observed anisotropy mainly comes from the upper asthenosphere at ~ 250 km and can be explained by a simple geodynamic model invoking absolute plate motion related to simple shear in the lithosphere-asthenosphere transitional layer and mantle flow deflected by the thick lithospheric root of the basin in the upper asthenosphere. In the vicinity of the 2019 Ridgecrest M7.1 earthquake sequence, significant spatial variations in the orientation and formation mechanisms of azimuthal anisotropy are observed. Specific findings include along-strike variations in fault zone width, an asymmetry in rock strength across the main fault in the area, confirmation of a proposed blind fault, and a temporal change in the orientation and strength of anisotropy that may reflect healing of fractures that were activated by the earthquake sequence"--Abstract, p. iii

Advisor(s)

Liu, Kelly H.
Gao, Stephen S.

Committee Member(s)

Grote, Katherine R.
Imqam, Abdulmohsin H.
Shi, Ying

Department(s)

Geosciences and Geological and Petroleum Engineering

Degree Name

Ph. D. in Geology and Geophysics

Publisher

Missouri University of Science and Technology

Publication Date

Fall 2022

Pagination

xiii, 80 pages

Note about bibliography

Includes_bibliographical_references_(pages 76-79)

Rights

© 2022 Yan Jia, All Rights Reserved

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 12195

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