Crustal Anisotropy and Ductile Flow beneath the Eastern Tibetan Plateau and Adjacent Areas

Abstract

Crustal anisotropy beneath 71 broadband seismic stations situated at the eastern Tibetan Plateau and the Sichuan Basin is investigated based on the sinusoidal moveout of P-to-S conversions from the Moho and an intra-crustal discontinuity. Significant crustal anisotropy is pervasively detected beneath the study area with an average splitting time of 0.39 ± 0.18 s. The resulting fast orientations are mostly parallel to the major shear zones in the Songpan-Ganzi Terrane, and can be explained by fluid-filled fractures, favoring the model of rigid block motion with deformations concentrated on the block boundaries. In the vicinity of the Xianshuihe-Xiaojiang Fault Zone in the southern Songpan-Ganzi Terrane, our results, when combined with previously revealed high crustal Poisson's ratio in the area, support the existence of mid/lower crustal flow. The Longmenshan Fault Zone and adjacent areas are dominated by strike-orthogonal fast orientations, which are consistent with alignments of cracks associated with compressional stress between the Plateau and the Sichuan Basin. The observations suggest that crustal thickening is the main cause of the high topographic relief across the Longmenshan Fault Zone.

Department(s)

Geosciences and Geological and Petroleum Engineering

Research Center/Lab(s)

Center for High Performance Computing Research

Keywords and Phrases

Seismology; Tectonics; Broad-Band Seismic Stations; Crustal Flow; Crustal Thickenings; Eastern Tibetan Plateau; Longmenshan Fault Zone; Receiver Functions; Seismic Anisotropy; Tibetan Plateau; Anisotropy; Block Rotation; Crustal Structure; Crustal Thickening; Deformation Mechanism; Fault Zone; Moho; P-Wave; S-Wave; Seismic Anisotropy; China; Longmenshan Fault Zone; Qinghai-Xizang Plateau; Sichuan; Sichuan Basin; Xianshuihe Fault Zone; Xiaojiang Fault Zone; Yunnan

International Standard Serial Number (ISSN)

0012-821X

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2016 Elsevier, All rights reserved.

Publication Date

01 May 2016

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