[S02-3] Studies of seismicity at Koyna, India

[S02-3-03] Crustal Configuration beneath Koyna-Warna Seismicity Region, Western India

^○Vm Tiwari¹, S Mishra², CP Dubey³ (1.CSIR-National Geophysical Research Institute, Hyderabad, India, 2.BGRL- Ministry of Earth Science Karad, India, 3.ESSO-National Centre for Earth Science Studies, Thiruvananthapuram, India)

invited

We present a 3D upper crustal configuration beneath Koyna-Warna region, western India, a site of continued seismicity over five decades in the continental interior. Seismic activities in the region are considered as a consequence of triggering of critically stressed regime due to artificial reservoirs. In order to delineate subsurface density and susceptibility models, Airborne Gravity Gradiometer and high-sensitivity Magnetic data (AGGM) are jointly inverted with constrained from several boreholes drilled through basalt exposed in this region. Model suggests an anomalous N-S oriented high density zone bound by low density rocks on either side in the north of Warna reservoir. Other prominent features are NW-SE oriented high and low density zones, south of Warna reservoir. The densities of sub-basalt rocks vary from 2650 to 2800 kg/m3. Interestingly, the majority of earthquakes are located at the contacts between rocks of contrasting densities.