TY - JOUR

T1 - 3-D seismic tomography of the lithosphere and its geodynamic implications beneath the northeast India region

AU - Raoof, J.

AU - Mukhopadhyay, S.

AU - Koulakov, I.

AU - Kayal, J. R.

PY - 2017/5/1

Y1 - 2017/5/1

N2 - We have evolved 3-D seismic velocity structures in northeast India region and its adjoining areas to understand the geodynamic processes of Indian lithosphere that gently underthrusts under the Himalayas and steeply subducts below the Indo-Burma Ranges. The region is tectonically buttressed between the Himalayan arc to the north and the Indo-Burmese arc to the east. The tomographic image shows heterogeneous structure of lithosphere depicting different tectonic blocks. Though our results are limited to shallower depth (0–90 km), it matches well with the deeper continuation of lithospheric structure obtained in an earlier study. We observe low-velocity structure all along the Eastern Himalayas down to ~70 km depth, which may be attributed to deeper roots/thicker crust developed by underthrusting of Indian plate. Parallel to this low-velocity zone lies a high-velocity zone in foredeep region, represents the Indian lithosphere. The underthrusting Indian lithosphere under the Himalayas as well as below the Indo-Burma Ranges is well reflected as a high-velocity dipping structure. The buckled up part of bending Indian plate in study region, the Shillong Plateau-Mikir Hills tectonic block, is marked as a high-velocity structure at shallower depth. The Eastern Himalayan Syntaxis, tectonic block where the two arcs meet, is identified as a high-velocity structure. The Bengal Basin, tectonic block to the south of Shillong Plateau, shows low velocity due to its thicker sediments. Based on the tomographic image, a schematic model is presented to elucidate the structure and geodynamics of Indian lithosphere in study region.

AB - We have evolved 3-D seismic velocity structures in northeast India region and its adjoining areas to understand the geodynamic processes of Indian lithosphere that gently underthrusts under the Himalayas and steeply subducts below the Indo-Burma Ranges. The region is tectonically buttressed between the Himalayan arc to the north and the Indo-Burmese arc to the east. The tomographic image shows heterogeneous structure of lithosphere depicting different tectonic blocks. Though our results are limited to shallower depth (0–90 km), it matches well with the deeper continuation of lithospheric structure obtained in an earlier study. We observe low-velocity structure all along the Eastern Himalayas down to ~70 km depth, which may be attributed to deeper roots/thicker crust developed by underthrusting of Indian plate. Parallel to this low-velocity zone lies a high-velocity zone in foredeep region, represents the Indian lithosphere. The underthrusting Indian lithosphere under the Himalayas as well as below the Indo-Burma Ranges is well reflected as a high-velocity dipping structure. The buckled up part of bending Indian plate in study region, the Shillong Plateau-Mikir Hills tectonic block, is marked as a high-velocity structure at shallower depth. The Eastern Himalayan Syntaxis, tectonic block where the two arcs meet, is identified as a high-velocity structure. The Bengal Basin, tectonic block to the south of Shillong Plateau, shows low velocity due to its thicker sediments. Based on the tomographic image, a schematic model is presented to elucidate the structure and geodynamics of Indian lithosphere in study region.

KW - geodynamics

KW - northeast India

KW - seismicity

KW - tectonics

KW - tomography

KW - FAULT PLANE SOLUTIONS

KW - TIBETAN PLATEAU

KW - SHILLONG PLATEAU

KW - BENGAL BASIN

KW - FOCAL DEPTHS

KW - BURMESE ARC

KW - EURASIA COLLISION

KW - CRUSTAL STRUCTURE

KW - OBLIQUE PLATE CONVERGENCE

KW - 1897 ASSAM EARTHQUAKE

UR - http://www.scopus.com/inward/record.url?scp=85019832377&partnerID=8YFLogxK

U2 - 10.1002/2016TC004375

DO - 10.1002/2016TC004375

M3 - Article

AN - SCOPUS:85019832377

VL - 36

SP - 962

EP - 980

JO - Tectonics

JF - Tectonics

SN - 0278-7407

IS - 5

ER -