The U.S. Bureau of Reclamation conducted studies on dams in 1976 and determined that Jackson Lake Dam was susceptible to failure in case of an earthquake of magnitude 5.5 or greater . Following the Borah Peak earthquake of 1983 in Idaho , the dam was upgraded during 1986 – 1989 , and the Bureau of Reclamation believed it could withstand the " maximum credible earthquake , " a magnitude 7.5 quake on the Teton fault . Since then various studies have cast doubt on this belief
Borah Peak earthquake
1983 Borah Peak earthquake
Jackson Lake Dam