Written records from local monasteries refer to strong ground-shaking over the past several thousand years. But the researchers don't have much evidence as to how frequent major earthquakes occur on the fault, or when it may happen again. "The Riasi fault isn't prominent on hazard maps for earthquake activity, but those maps are usually based more on the history of seismic activity rather than the potential for future events," said Andrew Meigs, a geology professor in OSU's College of Earth, Ocean, and Atmospheric Sciences and co-author on the study. "In actuality, the lack of major earthquakes heightens the likelihood that seismic risk is high.