Upper mantle seismic anisotropy beneath Myanmar from shear wave splitting
Abstract
From west to east, Myanmar is composed of the Indo-Burma Range (IBR), the Central Lowland and the Shan Plateau. The tectonic structures of Myanmar are mainly controlled by the converging process of the India Plate underneath the Burma Plate from west to east, and upper mantle seismic anisotropy provides us an unique constraint on the character of its lithosphere deformation and subduction zone mantle flow. Here, we present new measurements of XKS (SKS, SKKS and PKS) shear wave splitting from 78 broadband seismic stations in Myanmar, 71 stations of them from the China-Myanmar Geophysical Survey in the Myanmar Orogen (CMGSMO), and the remaining 7 stations from the Incorporated Research Institutions for Seismology (IRIS).
In the study region, the fast polarization directions (FPDs) and delay times show regionalization patterns from west to east. In the Indo-Burma Range, the FPDs are consistently parallel to the strike of the orogen, with delay times of 2 s or more. In the Central Lowland, the FPDs are nearly NE-SW to the north, and NNW-SSE or NW-SE to the south on the west side of longitude 95.3°E while nearly N-S on the east side. Moreover, null measurements or abrupt azimuthal variations are also detected in several stations. The average delay times are approximate 1.1s. The FPDs in the Shan Plateau are NW-SE with delay times of approximate 1 s. Our results suggest that the upper mantle anisotropy of this region is mostly controlled by mantle flow induced by the northward movement of the India Plate with respect to the Burma Plate. This study was supported by the National Natural Science Foundation of China (grants 41490612, 91755214).- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.T31H0301F
- Keywords:
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- 8110 Continental tectonics: general;
- TECTONOPHYSICS;
- 8124 Earth's interior: composition and state;
- TECTONOPHYSICS;
- 8177 Tectonics and climatic interactions;
- TECTONOPHYSICS