Crustal structure from deep seismic soundings along the Koyna II (Kelsi-Loni) profile in the Deccan Trap area, India

The crustal depth section obtained from deep seismic soundings along the Koyna II (Kelsi-Loni) profile, which lies near latitude 18°N roughly in the east-west direction in that part of the Deccan Trap Maharashtra State, India, shows a number of reflection segments below the Deccan Traps down to the Moho discontinuity. A deep fault below the Deccan Traps 13 km east of Mahad divides the entire cross-section including the Moho boundary into two crustal blocks. The reflection segments show updip towards the west coast in the western block. The Moho discontinuity which is at a depth of 39 km near the deep fault starts rising towards the coast, reaching a depth of 31.5 km at the west coast. The eastern block is thrown up by 1.5 km with respect to the western block along the deep fault. A structural contour map of the Moho discontinuity for the Koyna reservoir area has been prepared from the present results and the crustal information obtained along the Koyna I profile (Kaila et al., 1979a), shows that the deep fault in the Koyna area is aligned in the NNW-SSE direction.