Analysis of the Cross-Correlation between Seismicity and Water Level in the Koyna Area of India

The main objective of this study is the joint analysis of water level and seismicity recorded at Koyna (India), which is a unique site where reservoir-triggered earthquakes have been continually occurring over the last 50 years. Statistically significant cross-correlation coefficients between the daily water level and the daily number of earthquakes (with magnitudes greater than or equal to 2.2) suggest a time lag of 223 days, indicating reservoir-induced enhanced seismic activity mainly during the drawdown phase of the reservoir. The time lag and the mean earthquake depth provide a vertical hydraulic diffusivity of D similar to 0.2 m(2)/s for the area.