The U.S. Geological Survey said the strike-slip earthquake has already caused thousands of deaths and severe damage in the affected regions, and the final toll could be worse. The initial earthquake was one of the largest strike-slip earthquakes to occur on a continent in recent times. The first shock occurred at 4:17 a.m. local time on Monday and was 11 miles below the surface near the town of Gaziantep, Turkey, the USGS said.