Lake Mead is one of the world's largest reservoirs and was created by the construction of Hoover (formerly Boulder) Dam in the 1930's. Earthquakes were felt in September 1936, a few weeks after Lake Mead had reached its annual peak of about 100 m in maximum water depth. At the request of the Bureau of Reclamation, the Coast and Geodetic Survey began seismic investigations in 1937. A quadripartite net of short-period seismographs was installed in 1942 and operated until the early 1950's. Results of these investigations were reported by Mead and Carder (1941), Jones-(1944), Carder (1945), Carder and Small (1948), and Carder (1970).