Crustal Structure and Geodynamic Implications of the Indo-Burma Ranges and Surrounding Regions from Surface Wave Tomography and Receiver Function Analysis

To understand the implication of geodynamics in intercontinental subduction of Indian plate and Burmese plate, sediment deposits in the North-East India, Indo-Burma Ranges (IBR) and surrounding regions, a better resolved image is needed to interpret the findings. The structure and geodynamics in North-East India and surrounding region are studied using the fundamental mode rayleigh wave group velocity tomography. As there is a good coverage of stations in and around the region resulting in dense source-receiver pair ray cross paths, we get a better resolution than previously reported studies. The tomographic results show thicker sediments in Bengal Basin thins from west to east and crustal nature varies from north to south as continental to oceanic. The southern IBR shows consistent lower group wave velocity at all periods. Comparing both Bengal Basin and IBR, the velocity variation reveals about the oblique subduction of Indian plate below the Burmese plate. The Shillong Plateau and Mikir hills show low velocity at lower periods, but at higher periods it exhibits high velocity indicating presence of sediments in upper layers.
 
We present preliminary constraints on crustal structure beneath the Indo-Burma Ranges (IBR) using receiver functions from the IK (IISER Kolkata) and XR (BIMA) seismic network. Stacked radial receiver functions from these stations yield clear Ps and multiple phases, allowing stable H–κ estimates. Crustal thickness and V_p/V_s variation indicates notable heterogeneity in along East-West and North-South trend of IBR. Thicker crust in the central IBR and comparatively thinner crust towards the frontal zone likely reflect variations in deformation, composition and Indian plate – IBR convergence dynamics. These first order results provide essential inputs for upcoming high resolution imaging of the region.