Seismic Imaging of Koyna-Warna region using high frequency ambient noise tomography

The Koyna Warna Seismic zone (KWSZ) in the western India is a classic example of Reservoir Triggered Seismicity (RTS). The earthquakes in KWSZ are primarily related with reservoir. Since this region is totally covered by the Deccan basalt, therefore, few studies suggest role of variation in the basalt thickness for the seismicity in the KWSZ. Further, due to poor transmission of seismic energy trough trap, sub-basalt information is difficult. In the present study, we investigate basalt thickness variation in the KWSZ, to be used for further study of seismotectonics and geodynamics of the KWSZ. We conduct high frequency ambient noise tomography using dense network of ~100 short period seismic stations.  The 3-D shear velocity model (~10 km) beneath the KWSZ reveals distinct variation in the basalt thickness and sub-basalt crustal shear velocity structure.