Studies on the performance of carth dams in past carthquakes (Ambrasseys 1960, Seed et al. 1978) show very few fhilures, sruggesting. that the designs of most existing earth dams are qnite conservative. Conservatism is provide mainly by using gentle slopes, which may not be economical and may be impractical under the limitations of some new site conditions. Such an approach to the design of larger dams at seismically active sites, which are unsatisfactory in terms of foundation and abutment rock conditions, goemetry of the valley, and distance from borrow sites for fill material, will make their construction costs prohibitive. Clearly, the need for rational and economical design of earth dams is greater now than ever before.