Remobilization of the palaeoconvergent corridors hidden under the Deccan trap cover and some major stable continental region earthquakes

Intraplate seismicity over the Indian region seems to be highly correlated with the reactivated mobile belts -which, in turn, represent tectonic boundaries (TBs) or palaeoorogenic corridors - as evidenced from the fact that during the past 200 years most of the large earthquakes (M 6) over the subcontinent have occurred in the region strongly influenced by the Deccan trap (DT) eruption, Reunion plume activity and rifting during the Cretaceous and Tertiary periods. In this context, highly destructive Koyna and Latur earthquake regions, however, seem enigmatic because of being situated over the stable Indian shield. The present study examines and compares the results of some recent deep geophysical probings (including magnetotelluric, deep seismic sounding, teleseismic tomography, gravity and magnetic surveys) over both exposed parts of the Greater Dharwar Terrain (GDT) and its northern part hidden under the DT cover. This allows delineation of the northward extensions of the TBs of the GDT under the Deccan flood basaltic layer, and suggests that the Koyna and Latur regions may also be parts of the weak tectonic corridors along which different domains of the GDT (for example Western and Eastern Dharwar cratons, etc.) have accreted. It implies that parts of even the late Archaean TBs may also get reactivated if subjected to intense thermotectonic event (e.g. flood basaltic eruption). Thus like other intraplate earthquakes, those at Koyna and Latur too appear to be associated with reactivated TBs.