The findings suggest that even small man-made earthquakes, such as those of just a magnitude 1 or magnitude 2, can trigger damaging quakes, said study co-author Elizabeth Cochran, a seismologist with the U.S. Geological Survey.

 

"Even if wastewater injection only directly affects a low-hazard fault, those smaller events could trigger an event on a larger fault nearby," she told Live Science.

 

The Prague earthquake was the largest of thousands of quakes that rattled Oklahoma in late 2011. Three were magnitude-5 or stronger.