Old fault scars showed that earthquakes had occurred here before, and geologists recognized the faults were still active and predicted that the earth’s crust could break again in the same location as the last prehistoric quake. On Friday, October 28, 1983, the crust ruptured there, producing a 7.3 shock on the Richter Scale that spread 500 miles from the epicenter. The quake created the visible scar, or scarp, and dropped Thousand Springs Valley about 7 1/2 feet while the Lost River Range rose about a foot, both in a tilted manner.