PSI derived measurements of monsoon induced anomalous deformation before the earthquake swarm activity: a case study in the Saurashtra, Western India

The Saurashtra region, located south of the Kachchh M7.7 (2001) epicentre, has seen a few M5.0 earthquakes with dispersed seismicity over the past two decades. In the Amreli area, a sudden triggering of earthquake activity was noticed in the month of October 2021 - March 2022, and 172 earthquakes of M ≤ 3.0 were recorded within a radius of 10 km. Persistent Scatterer Interferometry (PSI) time-series results of Sentinel 1 A dataset (2017–2022) show the seasonal variation in the displacement and indicate anomalous behaviour with a displacement amplitude, up-to 8 mm, before the earthquake activity. The coefficient correlation (R²) of 0.78 between precipitation and Land Water Storage (LWS) accomplish that the risen displacement amplitude is directly linked with the high LWS which change the pore pressure as well as the stress level of the existing faults in the subsurface and ultimately triggers the earthquake swarm activity in this part of the Indian plate.