"Fault lines dating back hundreds of millions of years in Oklahoma that have been recently reactivated could lead to a devastating quake in the state where many structures were not built to withstand major seismic activity, a report said.

The state, which has seen several hundred seismic events over the past five years, has 'a high degree of potential earthquake hazards,' according to the study accepted for publication this month whose authors include researchers from the U.S. Geological Survey (USGS).

'The majority of the recent earthquakes in central Oklahoma define reactivated ancient faults at shallow depths in the crust' of less than 3.7 miles (6 km), said the report for the American Geophysical Union."

Jon Herskovitz reports for Reuters March 17, 2015. [2]