Lower mantle anisotropy beneath the Indo-Burmese Wedge through Shear Wave Splitting of Core-Refracted Phases

The Indo-Burmese Wedge (IBW) is a complex geological environment comprised of active deformation, subduction, and accretion processes. It is situated near the tectonic intersection of the Indian and Burmese plates. We examine the lower mantle anisotropy beneath IBW using the shear wave splitting (SWS) analysis of teleseismic phases to decipher the impact of lower mantle contribution and mantle dynamics beneath the IBW, even though limited research has been carried out to understand upper mantle dynamics. Here, we examine the role of lower mantle anisotropy beneath the IBW using differential phase combinations like SKS-SKKS and PKS-PKKS. Using the robust shear wave splitting approach, we analyzed data from 17 broadband seismic stations spread across the IBW and obtained around 57 pairs of discrepant results. Our findings show significant and comparable anisotropy in the lower mantle beneath the IBW, which may be caused by differential flow alignment consequence and anisotropic intensity in the deep mantle and subducted slab compared to the lithospheric deformation. These results demonstrate the way the lower mantle contributes towards the geodynamic environment and its wider ramifications for mantle dynamics in subduction zones around the IBW region.

Key Words: Seismic anisotropy, Lower mantle, Indo-Burmese Wedge, Subduction Zone, Shear Wave Splitting