The Kachchh region in western India has seen sustained intra-plate seismicity for the last few decades; many causal mechanisms have been suggested. In this study precise hypodd relocations of 2420 aftershocks delineate the causative fault zone of the 2001 Bhuj mainshock consisting of three main fault segments viz. the south-dipping north as well as south Wagad faults, and north dipping Kachchh mainland fault. Seismicity relocations (during 2001–16) also detect two seismicity clusters beneath the main aftershock zone i.e. Eastern (A1) and Western (A2). Our study also maps two mafic plutons beneath the A1 and A2 seismicity clusters, through local earthquake tomography. A rotation of 44° in the σ1-orientation within the aftershock zone has been detected through stress inversion of P- and T-axes from selected focal mechanism solutions, which could be attributed to large local stresses induced by mafic plutons. Our results suggest the mafic pluton induced crustal seismicity in Kachchh, Gujarat, India, for last 18 years.
Journal of Asian Earth Sciences 190 (2020) 104196