Internal structure of India: perspectives from a review of the seismological imaging studies from 2020 to 2023

The Indian subcontinent is a mosaic of different provinces exhibiting diversity in age, geology, elastic strength, tectonics, and seismicity. The evolution of most of the provinces from the Archean to the present age is not yet fully understood, which is further complicated by the active continent–continent collision along the northern margin and other intraplate forces. Seismological imaging helps unravel various subsurface structural features, thereby enabling a better understanding of the tectonic evolution. In the last 4 years, several seismological imaging studies have been carried out by Indian scientists, which has resulted in a remarkable improvement in depth estimation and constraining the geometry of important discontinuities, such as the Main Himalayan Thrust (MHT) and the Moho. Since the MHT plays an important role in generating megathrust earthquakes in the Himalaya, a large number of studies have been carried out in the Himalaya and their number almost equals the combined studies carried out in the rest of India. Detailed velocity structure of the crust and mantle has been estimated by tomographic inversion throughout the Indian subcontinent, even including Tibet, Pamir and Burma in certain cases. Attempts have also been made to estimate the depth and topography of deeper structures such as Hales discontinuity, Lithosphere–Asthenosphere Boundary, Mantle transition zones, and D’’ layer over the Core Mantle Boundary. Some of the studies have developed and adopted newer methodologies to map the structure. Those studies are analysed here to provide an overview of the progress toward understanding the structure.