Level divergences, seismic activity, and reservoir loading in the Lake Mead Area, Nevada and Arizona

In an earlier report [Carder, 1945], maps showing the epicenters of nearly 500 small local shocks in the Lake Mead area, Nevada and Arizona, were published. They showed a concentration of these epicenters along the south border of the basin occupied by the lower lobe of the lake. It was concluded that many of these local earthquakes were caused by a downfaulting of the crustal block occupied by this arm of the Lake against the granitic masses to the southeast and southwest. It was mentioned that this downsettlement was probably a renewal, on a small scale, of pre‐Pleistocene activity under the stimulus of a suddenly added load of 12 billion tons of water. Supporting evidence for this conclusion is the subject of the present paper.