Geologic mapping and earthquakes in southeastern Idaho

On April 14, 1973, a magnitude 4.75 earthquake occurred in Oneida County, Idaho. The intensity of ground motion was too slight to cause damage, and local interest in this event was so slight that it was not even noted in the weekly newspaper, the Idaho Enterprise, published in Malad City, the county seat. Two years later, an earthquake of magnitude 6.1 and three shocks, each of a magnitude greater than 4, occurred in nearly the same place under Pocatello Valley (fig 1). The main shock on March 27, 1975, was the strongest in the United States since the 1971 San Fernando Valley, Calif., event and was reported in newspapers across the country.