Characteristic features of June 14, 2020 earthquake (Mw5.3) of Kachchh Rift Basin in the Deccan Volcanic Province of Western India: a case of complex intraplate event

The Kachchh Rift Basin (KRB) is a very peculiar region in the Indian subcontinent mostly due to the intense seismic activity and intricate tectonics that is located far from the active plate boundaries. The KRB region is located in the Deccan Volcanic Province of Western India. Recently, a moderate earthquake (Mw5.3) occurred in this region on June 14, 2020, that was followed by ~ 22 earthquakes (M ≤ 4.6) until June 23, 2020. This moderate-size event falls about 12 km SSE from the 2001 Bhuj earthquake (Mw7.6). The mainshock and aftershocks are found to be located in an area of ~ 20 × 20 km2 that is orienting NE-SW indicating the rupture area of the mainshock. Several pertinent questions arose for the recent moderate event as it was located in the vicinity of the 2001 mainshock. The estimated focal mechanism solution of the current event depicts reverse faulting with a small strike-slip component. The current seismic activity matches well with the south-dipping nodal plane that is akin to the South Wagad Fault (SWF) in the region. The Coulomb failure stress change (∆CFS) caused due to the 2020 mainshock, considering the source as a receiver fault, clearly demonstrates the locations of aftershocks in the zone of compression that corroborates well with the south-dipping source. Such a strong correlation between the static stress changes and the aftershocks indicated SWF as the causative source. Interestingly, we found that the recent earthquake sequence has occurred in the shadow zone of the 2001 Bhuj mainshock. The coseismic deformation due to the 2020 mainshock was also obtained using an InSAR interferogram that demonstrated coseismic subsidence of ~ 3.6 cm close to the source zone, which is found to be consistent with the activity along with the south-dipping SWF. In addition, the low seismic velocities (Vp, Vs), high Vp/Vs ratio, and positive Coulomb stress changes suggest entrapped magma fluid in the seismogenic rock matrix, which probably played a significant role in triggering earthquakes in the study region. We validated our observations with the earlier seismological, geophysical, and geological shreds of evidence.