A University of Utah study says the Crandall Canyon mine collapse that trapped six miners last summer covered 50 acres and probably only lasted a few seconds.
Nine men died as a result of the Aug. 6 collapse and another cave-in 10 days later the six trapped miners and three who died trying to rescue them.
The study by university seismologists says the collapse began near where miners were excavating coal and quickly grew to a 50-acre cave-in.
Seismologists say the miners probably wouldn't have had any time to escape the collapse.
Following the disaster, the federal Mine Safety and Health Administration launched an investigation into what happened. Utah also formed an Office of Coal Mine Safety.