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Stress orientations and driving forces in the Indo-Burma plate boundary zone

Patcharaporn Maneerat, Douglas S. Dreger and Roland Burgmann
Stress orientations and driving forces in the Indo-Burma plate boundary zone
Bulletin of the Seismological Society of America (February 2022) 112 (3): 1323-1335

Abstract

The Indo-Burma range (IBR) is the forearc of an oblique subduction zone where the Indian slab obliquely converges with the Burma microplate. In this study, we consider earthquake focal mechanisms to help elucidate the tectonic behavior of the region. Toward this end, we examine the spatially variable stress orientations across the IBR and in the downgoing plate to better understand the associated plate driving forces and subduction dynamics. We combined earthquake focal mechanisms from 1 January 1950 until 31 December 2019 from a number of available catalogs and published studies, and divided the total of 189 events into spatial subdomains before performing stress inversions to document the spatial variability of the stress tensor. Generally, the maximum principal stress (S1) is oriented approximately north-south in all domains, subparallel to the subducting slab. The intermediate principal stress (S2) is plunging westward at variable angles. In contrast, the minimum principal stress (S3) is plunging to the east roughly following the dip of the subducting plate, indicative of down-dip tension in the slab. We do not observe a significant variation of the S1 orientation with depth, suggesting that north-south compression is due to the slab pushing northward through the mantle. Due to the well-defined slab-dip-parallel S3 direction for the megathrust and upper plate catalogs, the primary driving force of this subduction region is likely to be a net slab pull. Based on the seismic activity of the region, the consistency of focal mechanism-based stress and regional tectonic driving forces, as well as the S3 evidence for slab-pull forces, the possibility that the IBR can produce large earthquakes cannot be ruled out.


ISSN: 0037-1106
EISSN: 1943-3573
Coden: BSSAAP
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 112
Serial Issue: 3
Title: Stress orientations and driving forces in the Indo-Burma plate boundary zone
Affiliation: University of California, Berkeley, Earth and Planetary Science Department, Berkeley Seismology Laboratory, Berkeley, CA, United States
Pages: 1323-1335
Published: 20220208
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 41
Accession Number: 2022-011448
Categories: Solid-earth geophysicsSeismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, sketch maps
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 202210

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