Mid-continent gravity 'high' and seismic activities in central India

摘要

The epicenter of Jabalpur earthquake on 22 May 1997 coincides with a NE-SW oriented gravity gradient at the northern margin of Satpura Mobile Belt (SMB) extending from west coast of India up to central India. The width and amplitude of this gravity gradient coincide with Narmada-Son lineament (NSL) and suggest a system of faults north and south of Jabalpur, which is also confirmed by similar gradients in airborne and ground total intensity maps. The epicenter of several other seismic activities such as those around Khandwa during 1993-1996 and near west coast of India including Broach earthquake also coincides with this gravity gradient indicating its active nature. Significantly there are intersections of cross trends with the gravity gradient in the epicentral areas of the above-referred seismic activities. The epicenter of Jabalpur earthquake coincides exactly where this gravity gradient changes its direction from NE-SW to NNE-SSW which appears to be an intersection of two similar oriented faults. The gravity gradient is the northern margin of the mid-continent linens gravity high which in Jabalpur section is caused by the high density body in the middle crust. This high density body may represent magmatism related to paleorifts such as Mahakoshal Proterozoic rift exposed in the surrounding regions. As the hypocenter of Jabalpur earthquake is in the lower crust at the northern margin of the inferred high density body, it appears to be related to it. [References: 14]