Title

Seismic Anisotropy and Mantle Flow Constrained by Shear Wave Splitting in Central Myanmar

Abstract

This study represents the first campaign-style teleseismic shear wave splitting (SWS) investigation of central Myanmar, an area that is tectonically controlled by the oblique subduction of the Indian Plate underneath the Eurasian Plate. The resulting 678 well-defined and 247 null SWS measurements obtained from recently deployed 71 broadband seismic stations show that the Indo-Burma Ranges (IBR) possess mostly N-S fast orientations that are parallel to the trend of the depth contours of the subducted slab. Relative to the global average of 1.0 s, extremely large splitting times with station-averaged values ranging from 1.28 to 2.79 s and an area-averaged value of 2.09 ± 0.55 s are observed in the IBR. In contrast, the Central Basin (CB) and the Shan Plateau (SP) are characterized by slightly larger than normal splitting times. The fast orientations observed in the CB are mostly NE-SW in the northern part of the study area, N-S in the central part, and NW-SE in the southern part. The fast orientations change from nearly N-S along the N-S oriented Sagaing Fault, to NW-SE in the central and eastern portions of the SP. These observations, together with SWS measurements using local S events, crustal anisotropy measurements using P-to-S receiver functions, and the estimated depth of the source of anisotropy using the spatial coherency of the splitting parameters, suggest the presence of a trench-parallel sub-slab flow system driven by slab rollback, a trench-perpendicular corner flow, and a trench-parallel flow possibly entering the mantle wedge through a slab window or gap.

Department(s)

Geosciences and Geological and Petroleum Engineering

Comments

This study is supported by National Natural Science Foundation of China (grants 91755214, 42030309, and 41490612). The data analysis component is partially supported by the United States National Science Foundation under awards 1830644 and 1919789.

Keywords and Phrases

Central Myanmar; Mantle Flow; Oblique Subduction; Seismic Anisotropy; Shear Wave Splitting

Geographic Coverage

Myanmar

International Standard Serial Number (ISSN)

2169-9356; 2169-9313

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2021 Wiley, All rights reserved.

Publication Date

01 Oct 2021

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