Low deformation rate in the Koyna–Warna region, a reservoir triggered earthquake site in west-central stable India

Abstract We analyse nine years of GPS measurements of crustal deformation from the Koyna–Warna region within the stable India plate. The Koyna–Warna region experienced a strong earthquake on 10 December 1967 ( M 6.3) that is considered to have been induced by the impoundment of the Koyna reservoir and the continuing earthquake activity in the region is considered to be associated with the Koyna and Warna reservoirs. The earthquakes occur in a very small region of 30 × 10 km 2 in two well defined seismic zones, the NNE–SSW trending Koyna Seismic zone, and the NNW–SSE trending Warna Seismic Zone. These zones are characterised by predominantly left-lateral strike slip motion and normal motion, respectively. In 2003, we initiated campaign-mode GPS measurements in the region. Analysis of the GPS data collected over nine years indicate low to moderate deformation rate (