Lessons from Bhuj

Sir, - Although the latest Bhuj earthquake of Gujarat was not unexpected, its timing and magnitude could not be predicted by the Indian experts. The Kutch quake of 1956 of magnitude 7 on the Richter scale produced an intensity of 10 magnitude on the Modified Mercalli scale as it had a shallow depth of 23 kilometres and naturally produced high peak ground accelerations. The Koyna earthquake of 6.5 magnitude also caused havoc due to high peak ground accelerations due to its shallow depth. The Nahanni quake of Canada of magnitude 6.6 produced ground accelerations 1.25 to 2 times the acceleration due to gravity in 1985 due to low focal depth.

In the light of destructive impacts of Uttarkashi, Chamoli, Kobe and El Salvador earthquakes, the Government of India must not blindly believe the assurances given on the safety aspects of the designs of Sardar Sarovar, Tehri, Koyna and Mullaperiyar dams because they are underdesigned by using low seismic coefficients even though they are located in close proximity to the major earthquake highways.

Karnataka made an assessment of the dam-burst scenario due to the failure of Koyna dam and found that Hippargi, Almatti and Narayanpur dams in Karnataka and Srisailam and Nagarjuna Sagar in AP may be damaged due to maximum credible accident to Koyna. Since the Mullaperiyar dam was not designed to withstand the maximum credible earthquakes, the proposal to raise its height must be stopped as requested by Kerala.

Since comprehensive environmental impact and disaster management reports have not been prepared and subjected to public hearing, the proposed increase in the height of Sardar Sarovar and Almatti dams should be suspended and the Tehri dam project be converted into a run-off river scheme. The western countries should not only render financial assistance to India during these natural calamities but they should help the Indian Government to design its major irrigation and hydro-power projects with sound scientific and technical data for ensuring their safety and sustainable development of the country.

T. Shivaji Rao,

An environmentalist

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