Researchers have devised a technology that can distinguish mine collapses from other seismic activity.

New calculations show that the deadly Crandall Canyon mine collapse – which registered as a magnitude-3.9 earthquake – began near where miners were excavating coal and quickly grew to a 50-acre cave-in, University of Utah seismologists say in a report on the tragedy.

A 3.9 magnitude temblor recorded at the time of a mine collapse in southern Utah on Monday, Aug. 6, was not from an earthquake, but more likely the result of the collapse itself, according to an analysis by University of California, Berkeley, seismologists.