A Borehole Geophysics Research Laboratory (BGRL) is being established by the Ministry of Earth Sciences at Karad to address challenging seismological problems of societal relevance through drilling investigations. BGRL was conceptualized as part of the Ministry’s programme of Scientific Deep Drilling in the Koyna Intra-plate Seismic Zone for geological investigations and modelling, dedicated to earthquake research in the area.
Reservoir triggered earthquakes have been occurring persistently in the Koyna region since the impoundment of the Shivaji Sagar Lake in 1962. The 6.3 magnitude Koyna earthquake in 1967 is the largest triggered earthquake in the world. Till date, 22 earthquakes of magnitude 5 and above and several thousand smaller earthquakes have occurred in the region. All earthquakes are restricted to an area of 30 km x 20 km only. A strong correlation between continued earthquake activity and the annual loading and unloading cycles of the Koyna and nearby Warna reservoirs has been established. However, a model to comprehend the genesis of reservoir triggered earthquakes is elusive, due to lack of observations from near-field.
It is proposed to drill deep boreholes to reach the depths of earthquakes and set-up a deep borehole observatory. Direct observations in the source zone of the earthquakes will provide new and critical information to model these earthquake mechanisms.