High precision earthquake locations in Koyna‐Warna seismic zone reveal depth variation in brittle‐ductile transition zone

Abstract

The Koyna‐Warna region located in the southwestern part of Deccan Volcanic Province is known for sustained seismicity during the last four decades. Catalog P and S phase data of local earthquakes recorded by the Koyna‐Warna digital network were used to relocate 609 earthquakes using double difference algorithm. The relocated seismicity patterns delineate the presence of three fault segments and variation in the brittle–ductile transition depths amongst the individual faults as the earthquake foci in the north are limited up to 11 km depth whilst in the south they are confined up to 6–8 km. The focal mechanism solutions also indicate distinct styles of faulting amongst the three inferred fault segments. The variation in brittle‐ductile transition zone is probably controlled due to the geometry of the fault system and the effective stress.