Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

Abstract

Detailed structural interpretation of the regional gravity map over the Deccan traps has brought out a number of major structural discontinuities (fault/fractures), particularly the E-W features whlch were not delineated by earlier investigators. The most significant among them is the major E-W fault from west coast to east coast along Bombay-Latur-Hyderabad-Bhadrachalam-Visakhapatnam (BLHV fault). Several features of the BLHV fault suggest it to be a major reactivated strike slip fault. The structural scenario presented in this paper will have great implications in earthquake studies in Deccan trap area. Based on some aspects of fault segmentation technique for earthquake hazard and from the structural interpretation of the regional gravity map over Deccan traps, several zones are identified which could be termed as earthquake hazard zones. These hazard zones are typically located at: (1) the segment boundaries or fault steps of BLHV and other major E-W faults, (2) in many cases are associated with gravity low nosings which possibly reflect buried granite intrusions (regarded as asperities or barriers in the context of seismicity), and (3) intersection of major E-W faults with other transverse structural trends (fault/fractures). The areas where the major E-W faults terminated against the west coast fault system can also be important in terms of future seismicity. The recent seismicity in the Deccan trap, area is inferred to be due to the reactivation of the major E-W faults due to the still continuing convergence of India with Asia.

The present work, for the first time, demonstrates the importance and application of fault segmentation technique in earthquake hazard studies in Deccan trap area, and also the full potential of gravity interpretation in such studies.

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