rediff.com: Koyna dam is safe: PTI

The Koyna dam, in one of the most seismic-prone zones of Maharashtra, suffered no damage due to the earthquake which struck parts of Maharashtra early on Tuesday, according to Koyna hydroelectric project chief engineer N Huddar.

The accelerograph on Koyna dam recorded an acceleration of 0.13 G (gravitational acceleration) in the body of the dam, he told PTI. The accelerograph measures the rate of change of velocity in the dam due to earthquakes. The acceleration recorded by the accelerograph is an important parametre regarding the dam's safety, he said. Accelerations are recorded only in cases of quakes of high intensity.

The shock is the eighth highest intensity quake since 1963, whose magnitude exceeded five on the Richter scale. This region has witnessed over one lakh earthquake shocks since 1963.

The dam, at Koyna Nagar in Patan taluka of Satara district, is a highly active seismic zone and its Shivajisagar reservoir has a capacity of 2797 million cubic metres of water.

According to a report from Hyderabad, Tuesday's earthquake in Maharashtra did not cause any major damage, but Indian geologists say the fault zone under the Koyna dam has been weakened by the annual reservoir filling.

They warned that with the passage of time the region would experience earthquakes even with slight fluctuations in reservoir level.

Kusala Rajendran and C M Harish at the Centre for Earth Sciences in Thiruvanathapuram claimed that the spatial and temporal patterns of recurring earthquakes in Koyna region suggest the possibility of the fault zone becoming further unstable, progressively lowering the stress needed to trigger an earthquake.

Their conclusion is based on an analysis of earthquakes in the region since Koyna experienced the first earthquake in 1967 five years after water was impounded in the reservoir.

Reporting their findings in Current Science, they said that seismicity associated with the Koyna reservoir was unique in the world as it is one of the few sites where earthquakes of magnitude greater than five continue to occur three decades after the initial spurt of activity.

Reservoir-induced earthquakes have occurred in other parts of the world, but seismicity in these regions had tapered off with time, the scientists said. Persistence of moderate seismicity at Koyna is enigmatic as the Indian peninsular shield is a relatively stable region, they said.


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