Upper-mantle Structure beneath Myanmar by Teleseismic Body-wave Finite-frequency Tomography

Abstract:

Myanmar (Burma), as a part of the Eastern Himalayas Syntaxis, is a crucial region for understanding the collision between India and Asia and the evolution of the Neo-Tethyan Ocean. In this study, we present new tomography models of P- and S-wave velocity structures in the upper mantle beneath Myanmar region. The tomographic images were constructed using the teleseismic data from 138 temporary stations of the newly deployed China-Myanmar Geophysical Survey in the Myanmar Orogen (CMGSMO and CMGSMO II) seismic network, as well as other 615 seismic stations in Myanmar and its adjacent areas. Our tomographic models show three distinctive slab-like high-velocity structures beneath the Myanmar region. These structures exhibit roughly north-south–trending along the Burma arc. The high velocity anomaly beneath the western boundary of the western Myanmar extends vertically from the depth of ~100km to the base of mantle transition zone. The eastern-dipping high-velocity body beneath the Indo-Burma Ranges has a thickness of approximate 100 km and velocity perturbations of 2.0-4.0%. The high-speed anomaly beneath the eastern boundary of the western Myanmar block has a core velocity perturbation of 3.0% and a maximum depth extension of ~240 km. We speculate that these high-velocity structures may represent multi-stage Tethyan subduction.
This study was financially supported by the National Natural Science Foundation of China (grants 41490612 and 91755214).