The Moho architecture and Tectonic Settings of the Indian subcontinent and Tibetan plateau from gravity and seismic data analysis.

The geological terranes on the Indian subcontinent and Tibetan plateau are structurally and chronologically diverse. In this study, a nonlinear inversion is performed to estimate the Moho depths using the high-resolution global gravity model EIGEN-6C4 in combination with existing seismically derived Moho depth. A spherical approximation is utilized to correct and calculate the Bouguer effect, terrain effect, and sediment gravity effect. The inversion result shows the Moho throughout the Indian subcontinent varies range from a minimum of 28 km to a maximum of 75 km in depth. The crust is at its thinnest beneath northwest and eastern India. The Cenozoic continental collision between the Eurasians and Indian plates is attributed to the thickest crust (55 km) under the Himalayas and the Tibetan plateau. While the thicker Moho is distributed in the southern India shield which also shows convergence and collision of cratons during late Archean time. A comparison of the Moho depth from our study and a sediment-adjusted isostatic Moho model shows a varying buoyancy effect in the upper mantle under the region. The Tibetan plateau’s interior is mostly compensated, but its margins with steep topography have little compensation and are under-compensated. On the other hand, the region under southern India and the Indo-Gangetic plain is over-compensated. Most seismic events occurred in areas where the compensation rate amplitude suddenly changed. This observation led us to believe that isostasy may significantly impact seismic activity in the Himalayas and surrounding area.