Artificial Water Reservoir-Triggered Seismicity (RTS): Most Prominent Anthropogenic Seismicity

Under certain suitable geological conditions, anthropogenic seismicity due to gold/coal mining, geothermal and natural gas/oil production, filling of artificial water reservoirs, and high-pressure fluid injection has been reported globally. The reservoir-triggered seismicity (RTS) is most prominent, having been reported from hundreds of with at least five sites where earthquakes exceeding M 6 occurred, claiming human lives and destruction of properties. The most important correlate for RTS to occur is the height of water column in the reservoir. Certain common characteristics of the RTS sequences have been identified, which discriminate them from normal earthquake sequences. Factors influencing RTS include the highest water levels reached in the reservoir, duration of the retention of high-water levels and rate of loading/unloading. The mechanism of RTS is reviewed. The absence of knowledge of physical properties of rocks and fluids in the fault zone does not permit us to comprehend the RTS mechanism. Koyna, India, is found to be a very suitable site for such investigations as the earthquakes have been occurring in a small region of 20 x 30 km, at shallow depths (mostly within 8 km), with no other seismic source in the vicinity, and the region being accessible for all kinds of observation and investigations. The suitability of Koyna for setting up of a deep borehole laboratory was discussed during International Continental Drilling Program (ICDP) workshop in 2011 and accepted. Suggestions were made for some additional scientific works, which were completed during 2011-2014. The second ICDP workshop in 2014 approved of going ahead. A 3-km-deep Pilot Borehole has been completed in the vicinity of Donachiwada fault that hosted the main 10 December 1967 M 6.3 earthquake and several earthquakes of M similar to 5. The investigations being carried out are providing the necessary input to set up the proposed similar to 7-km-deep borehole laboratory. In this article, an overview of RTS globally and at Koyna, India, specifically is focused.

Automated summary

Under certain geological conditions, human-induced seismicity can occur due to activities such as gold/coal mining, geothermal and natural gas/oil production, filling of artificial water reservoirs, and high-pressure fluid injection. Reservoir-triggered seismicity (RTS) is the most prominent, with reported earthquakes exceeding M 6 and causing casualties and property destruction. The height of water column in the reservoir is the most important factor for RTS to occur.