Seismic Evidence of Pop-up Tectonics Beneath the Shillong Plateau Area of Northeast India

Our detailed analysis of high-quality arrival time data recorded by the local seismographic network using three-dimensional seismic tomography of the Shillong Plateau region using high-quality arrival times of the body wave phases recorded at a dense temporary seismic network. This technique is used to understand the heterogeneities of the crust and its implications for pop-up tectonics characterizing evaluation the of the Shillong Plateau. We investigated an area covering ~150 ×100 km 2 that revealed seismicity to be confined in a depth range ≤ 60 km. High - velocity anomalies in the upper crust appear to be responsible for intense small to moderate seismic activity in the region. Crustal seismic velocities inferred from 3-D seismic tomography showed significant lateral heterogeneities beneath the lithosphere of the Shillong Plateau. High-velocity anomalies in the uppermost crust, interpreted as the Shillong Plateau act as a geometric asperity where interseismic strain may accumulate. Low-velocity anomalies in the lower crust probably play a major role to accommodating the stresses generated due to plate separation, culminating in future sources of great earthquakes. The geological faults are well imaged in the cross-sections and support the concept of Pop-up tectonics beneath the Shillong of NE India.