Large Earthquake Forces on Gravity Dam

Abstract

ON December 10, 1967, at 22 h 5 min (GMT), western India was shaken by a severe earthquake. The epicentre of the shock was computed by the US Coast and Geodetic Survey at about 17.7° N.–73.9° E. and it lies in the Deccan Trap, an area so far considered to be seismically quiescent. This earthquake, which had a magnitude 6.5, belongs to a series of shocks that commenced after the first filling of the Koyna reservoir in 1962, and culminated in the December shock, followed by numerous strong aftershocks. The reservoir has a storage capacity of 2,000 million m³ and it has been created by the construction of a 100 m high concrete gravity dam^1,2. The occurrence of a destructive earthquake associated with the filling of a large artificial reservoir has been observed at Kremasta in Greece³, and the occurrence of smaller earthquakes accompanying the filling of a reservoir or rapid fluctuations of its level has been observed in other cases (Marathon Dam in Greece, Contra Dam in Switzerland, Kariba Dam in Rhodesia, Boulder Dam in the United States)⁴.