Seismic heterogeneities in the Indian lithosphere

Abstract

Rayleigh wave group velocity distributions over the Indian region were obtained, by the Backus-Gilbert method, for time periods 15, 25, 40, 50 and 60 s. The observed velocity variations reveal sharp lithospheric heterogeneities in this region. Southern peninsular India is marked by high velocities in contrast to the northern Indo-Gangetic plain and the Himalaya. Highest surface wave velocities are observed over the southern part of the Deccan traps and the Dharwar craton, whereas the metamorphic terrains and rift zones exhibit anomalous low velocities. The Nepal-Himalaya and Indo-Burmese collision zones are characterised by contrasting velocities, which reflect their diverse orogenesis. The Bay of Bengal is marked by an anomalous 6–12% higher velocity as compared with the Indian continental region, for the periods 25–50 s.