Of the 162 Texas earthquakes with magnitudes of 3 or greater between 1975 and 2015, the study categorized 42, or 26 percent, as “almost certainly” human-caused, and 53, or 33 percent, as “probably” human-caused. Only 13 percent of earthquakes were natural. The study was based on a review of journals and the historical catalog of Texas earthquakes from 1847 to 2015.
For Texas, the most noteworthy cases are the series of earthquakes at the Dallas-Fort Worth International Airport, and another series of quakes in the cities of Timpson and Azle. All three cases occurred in regions where prior seismic activity was unknown, according to the study, and all three had accurately determined epicenters some 1.2 miles from active injection wells.