Observations Made during and Immediately after the Earthquake

K oyna Earthquake of December 11, I967: Report of the Expert Committee on Electrical and Mechanical Equipment. UNESCO, No. 1489/BMS.RD/SCE, Paris , September, 1969, 52 pp. Hydroelectr ic power generators are common in seismic regions th roughou t the world and the i r abi l i ty to w i th s t and ea r thquakes is i m p o r t a n t to public welfare. There is very l i t t le informat ion in the l i te ra ture about the effects of ea r thquakes on such ins ta l la t ions ; hence, the repor t of the Exper t Commit tee should be of special in te res t to all who are responsible for designing and opera t ing hydroelectr ic plants . The repor t describes what happened at the power s t a t ion dur ing and af ter the ea r thquake and makes recommendat ions for improving the ea r thquake resistance. The magni tude 6.5 ear thquake , t hough t to have been tr iggered by the reservoir loading, centered about 3 km sou th of the dam. A s t rong-mot ion aecelerometer ins ta l led wi th in the 338-ft high, concrete g rav i ty dam recorded a peak accelerat ion of about 50 per cent g, wi th the frequencies in the mot ion being appreciably higher t h a n those shown by U. S. ear thquakes . The 540-MW electricgenerat ing s t a t i on was located about 8 km WNW of the dam. The effect of the ea r thquake on the dam has been described in a paper by G. V. Berg et al., The Koyna, Ind ia Ear thquakes , Proceedings of the Fifth World Conference on Earthquake Engineering, Santiago, Chile, 1969, and also in UNESCO Report of the Committee of Experts on Koyna Earthquake of December 11, 1967, New Delhi, 1968. The effect of the ea r thquake on the power genera t ing s t a t ion is summarized in the following descr ip t ion which has been abs t r ac t ed from the report .