Researchers: Rakesh Dumka and Pallabee Choudhury, Institute of Seismological Research, India; V. K. Gahalaut, National Center for Seismology, India; Kalpna Gahalaut, CSIR-National Geophysical Research Institute, India; and Rajeev Kumar Yadav Indian Institute of Technology, India.
Written by Linda Rowan
6 December 2019
GPS measurements of surface motion, vertical and horizontal, near four dams in India, show that the surface moves when the water volume of the dam changes. These observations show that the water volume of the dam affects the stress of the surrounding rock. Thus the dams may contribute to stress changes and deformation, particularly triggering earthquakes nearby.
Four dams in India, Tehri, Koyna, Dharoi and Ukai reservoirs, were investigated for surface deformation related to dam activity over seven years. Four permanent and continuously operated GPS sites (KUNR, GOKL, DHAR and SAGB), one near each dam, are maintained by CSIR-National Geophysical Research Institute, Hyderabad and Institute of Seismological Research, Gandhinagar, India. Using standard analysis, the authors evaluated the surface displacement at each site relative to information about the changing water volume of each dam. The GPS sites were corrected for atmospheric, hydrospheric and plate tectonic affects as well as seasonal changes that are not related to the dams. The GPS sites were also compared with other GPS sites that are farther away from each reservoir. The sites that are farther away and used for reference did not show as much movement as the sites near the dams.
The four reservoirs caused surface deformation that was measured by vertical and horizontal changes in the GPS sites when the water volume of each reservoir changed. Thus there is a direct correlation between the dams and changes in the near field stress. Other studies have documented earthquakes triggered by at least three of the dams and these new results contribute to the concern that dams in tectonically active regions can trigger earthquakes by increasing and changing the stress regime near the reservoirs.
Dumka et al., GPS Measurements of Deformation Caused by Seasonal Filling and Emptying Cycles of Four Hydroelectric Reservoirs in India, Bulletin of the Seismological Society of America, Vol. 108, No. 5B, pp. 2955–2966, November 2018, doi: 10.1785/0120170355.
stress, triggered earthquake, reservoir, dam
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