FAULT SEGMENTATION AND EARTHQUAKE HAZARD ZONES IN DECCAN TRAP REGION - GRAVITY EVIDENCE

Detailed structural interpretation of the regional gravity map over th e Deccan traps has brought out a number of major structural discontinu ities (fault/fractures), particularly the E-W features which were not delineated by earlier investigators. The most significant among them i s the major E-W fault from west coast to east coast along Bombay-Latur -Hyderabad-Bhadrachalam-Visakhapatnam (BLHV fault). Several features o f the BLHV fault suggest it to be a major reactivated strike slip faul t. The structural scenario presented in this paper will have great imp lications in earthquake studies in Deccan trap area. Based on some asp ects of fault segmentation technique for earthquake hazard and from th e structural interpretation of the regional gravity map over Deccan tr aps, several zones are identified which could be termed as earthquake hazard zones. These hazard zones are typically located at: (1) the seg ment 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 fault s with other transverse structural trends (fault/fractures). The areas where the major E-W faults terminated against the west coast fault sy stem can also be important in terms of future seismicity. The recent s eismicity in the Deccan trap, area is inferred to be due to the reacti vation 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 ear thquake hazard studies in Deccan trap area, and also the full potentia l of gravity interpretation in such studies.