Koyna-Warna is a region of low tectonic deformation and normal surface heat flow (~40 mW/m 2) in the Deccan volcanic province, India, where low-to-moderate-magnitude earthquakes have continued to occur in the last 60 years. These earthquakes are uniquely restricted to an 11×16 km 2 area and confined to the upper crust at 3-9 km depth. Located at the last phase of the interaction of India with the Reunion mantle plume ~65 Ma ago and responsible for extensive volcanism, the cause of sustained seismicity is a subject of academic debate. Using the shear wave velocity model derived through the joint inversion of the receiver function and surface wave data from a location of intense seismicity in the region, we propose that earthquakes in the Koyna region occur due to stress concentration arising because of the high density (velocity) magma intrusion at 3-9 km and 20-28 km depths. The high-density mafic/ultramafic body exerts a downward pull on the elastic upper crust, causing stress loading and earthquake occurrences in the shallow crust. The continuation of earthquakes in the deeper part is inhibited by the possible fluid-filled mush zone imaged as a low-velocity layer at a 9-15 km depth. The magma intrusion as dyke can induce a cycle of normal faulting in the overlying rock mass, as observed in the Koyna-Warna region. We present the first evidence of an extremely high velocity (>4.7 km/s) layer at 40-50 km below Moho, interpreted as the presence of eclogite-peridotite responsible for producing Deccan magma in large volume.
