Crustal velocity structure of western Dharwar Craton, South India

A deep seismic sounding (DSS) experiment was carried out across the Indian shield in 1972-1975. Kaila et al, (Kaila, K.L., Roy Chowdhury, K., Reddy, P .R., Krishna, V.G., Hari Narain, Subbotin, S.I., Sollogub, V.B., Chekunov, A.V., Kharetchko, G.E., Lazarenko, M.A., Ilchenko T.V., 1979. Crustal struc ture along Kavali-Udipi profile in the Indian peninsular shield from deep s eismic sounding. J. Geol. Sec. of Ind., 20, 307-333) presented a crustal de pth section based on the interpretation of the analog seismic data. In this paper, we re-examine the crustal structure of the Western Dharwar Craton ( WDC) by reprocessing the data of three major shot points. Kinematic 1-D inv ersion, followed by 2-D forward modeling of the first arrival refraction an d a few persistent wide-angle reflection phases, was carried out to build, a first order two-dimensional velocity model of this segment of the profile . This model brings out a simple crustal velocity structure consisting of a n upper and lower crust. The upper crust (velocity 6.0-6.2 km/s) is on aver age 23 km thick, which is underlain by a lower crust of velocity 6.8-7.0 km /s. The average Moho depth in this part is about 37-40 km, with higher-than -normal P-n velocity of 8.4 km/s. A relatively deep Moho in this part of th e Archean peninsular shield is associated with relatively low velocities in the lower crust, perhaps indicating absence of underplating in this region . Present results bring out the fact that the crust of WDC is not so typica l as many other Archean crusts, in terms of both thickness and velocities. (C) 2001 Elsevier Science Ltd. All rights reserved.