Crustal anisotropy and ductile flow beneath the eastern Tibetan Plateau and adjacent areas

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 beneat...

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Bibliographic Details
Published in:Earth and planetary science letters 2016-05, Vol.442, p.72-79
Main Authors: Kong, Fansheng, Wu, Jing, Liu, Kelly H., Gao, Stephen S.
Format: Article
Language:English
Subjects:
Anisotropy
Basins
Broadband
Cracks
crustal flow
Geological faults
Orientation
Poissons ratio
receiver functions
Rigid blocks
seismic anisotropy
Tibetan Plateau
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Summary: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. •We measure crustal anisotropy beneath eastern Tibetan Plateau and Sichuan Basin.•Major shear zones show large splitting times and strike-parallel fast orientations.•Crustal flow beneath Litang and crustal shortening beneath Longmenshan Blocks.
ISSN:0012-821X
1385-013X
DOI:10.1016/j.epsl.2016.03.003