Of dams and earthquakes
Little has been done in India to study dam-induced seismicity despite a lot of environmental heat and dust. To bridge the gap, B K Rastogi and R K Chadha of the National Geophysical Research Institute (NGRI) in Hyderabad have proposed to study the seismicity around the Koyna dam in Maharashtra.
The NGRI scientists claim that earthquakes began to occur soon after the impoundment of the Koyna reservoir in '64. Tragedy struck when about 200 people died in an earthquake of the magnitude of 6.3 on the Richter scale that devastated the Koyna township in '67. Since then, tremors of the damaging magnitude of at least 5 on the Richter scale have been recorded in '73, '80, '93 and '94. More alarming is the fact that seismicity is on the rise ever since the Warna reservoir, 30 km south of the Koyna dam, was filled up in '93. Ground cracks have appeared and walls have collapsed in villages of Satara, Sangli, Kolhapur and Ratnagiri districts.
The scientists point out that it is not possible to predict the location and depth of the earthquakes due to inadequate network of monitoring systems. The NGRI scientists propose to improve the scenario by establishing more monitoring stations and deploying digital seismographs.
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