Stress drop variations of triggered earthquakes at Koyna–Warna, western India: A case study

Study of the corner frequencies and stress drops of a new earthquake sequence that occurred during 1 May25 June 2017 has been conducted, along with dependency of stress drop with increasing seismic moment of these earthquakes. A total of 689 P-wave spectra of earthquakes recorded by a short-period borehole and a broad-band surface seismic network are utilized for this purpose. We found that the corner frequency varies from 1 to 25 Hz and stress drops vary from 0.01 to 14 MPa for earthquakes of both the clusters. The combined trend of median stress drop from both the clusters follows a constant stress drop scaling as widely accepted for natural tectonic earthquakes. The comparative low median stress drop value of earthquakes at the new cluster is possibly a consequence of heterogeneous slip due to the formation of micro-fractures on the fault, which was not active earlier.


C R MAHATO and D SHASHIDHAR (2022) J. Earth Syst. Sci. (2022)131:106; external link