Reservoir-Triggered Seismicity: Its Relevance to North East India- A Review

Abstract

The OFT NEGLECTED issue of Reservoir Triggered Seismicity (RTS) received attention following the earthquake in Wenchuan County, Sichuan Province, China (12th May 2008). Following the event, a major question raised was whether the earthquake was related to impoundment of nearby Zipingpu reservoir or the Three Gorges reservoirs on the river Yangtze. The accepted explanation relates to (i) extra water pressure created in the micro-cracks and (ii) fissures in the ground under and near a reservoir. This means when the pressure of the water in the rocks increases, it lubricates the faults that are already under tectonic strain, but are prevented from slipping by the friction of the rock surfaces. There have been number of cases of RTS around the world including India and numerous studies have been conducted to relate RTS with dam height (more height means more impoundment). As far as Brahmaputra basin is concerned, there is cause of concern because China intends to build twenty (20) dams to generate about 60,000 MW of power in Tsangpo/Brahmaputra and eleven (11) out of twenty (20) projects are to be located between the source of Tsangpo and the Great Bend. Dams on the straight course will generate 20,000 MW, while the balance of 40,000 MW will be generated at the Great Bend itself. Most of these are large projects with potential to trigger earthquake during impoundment. Like China, India too is planning to have around 170 dams on the tributaries of Brahmaputra, most having potential for RTS.