Structural fabric over the seismically active Kachchh rift basin, India: insight from world gravity model 2012

The Kachchh rift basin (KRB), located in the western continental margin of India, is very important due to repeated large magnitude occurrence of intraplate earthquakes. The present study elucidates the subsurface structural features using wavelength filtering, total horizontal derivative (THD) and 2.5 dimensional (2.5D) density modelling of the gravity data. Power spectrum analysis of the gravity data gives the cut-off wavelength of 100 km that has been used for wavelength filtering for regional-residual separation. The residual gravity anomaly significantly enhances the shallow features (like Allah-Bund fault, Kachchh mainland uplift, Wagad uplift, and Pachham uplift) and gives an NW-SE subsurface structural trend. The predominant direction for major lineaments derived by the THD of gravity data shows the ENE-WSW as well as NE-SW and NW-SE directions. The 2.5D density model of the regional gravity anomaly reveals the presence of high-density magmatic underplating layer and intrusive mafic body in the lower crust that is in accordance with the previous studies. The regional slope of the Moho in the KRB is towards the SW direction. An intrusive mafic body in the lower crust and volcanic plugs in the upper crust act as stress concentrator which is responsible for seismicity in the KRB. Several new lineaments have been identified based on the present study, which may be accountable for seismicity over the different part of KRB.