Koyna, India: A very prominent site of artificial water reservoir-triggered seismicity

Anthropogenic activities such as gold and coal mining, oil and gas production, filling of artificial water reservoirs, harnessing of geothermal energy, etc., have induced/triggered earthquakes. Koyna dam, located in the Deccan volcanic province of India, was impounded in 1962, and soon after tremors were reported from the vicinity of Koyna dam. The largest triggered earthquake of magnitude (M) 6.3 occurred on 10 December 1967. The triggered earthquakes have continued until now and the region has experienced 22 events of an M similar to 5, over 200 events of an M similar to 4 and several thousand smaller events. The reservoir-triggered seismicity has continued until 2021, which is unique. Some of the early investigations, leading to drilling of a 3 km deep pilot borehole at Koyna for near-field studies of earthquakes, and a few recent results are summarised in this paper.