Analysis suggests no quake in Utah mine collapse

By Dan Whitcomb

LOS ANGELES (Reuters) - Seismic activity detected in Utah at the same time a mine collapsed there, trapping six men deep underground, was probably caused by the cave-in itself and not an earthquake, U.S. geologists said on Tuesday.

But Harley Benz, scientist in charge of the National Earthquake Information Center in Golden, Colorado, said a final conclusion was still several days away.

The mine's owner has insisted that an earthquake was responsible for the collapse and lashed out at experts and members of the media who have said otherwise.

"To date our analysis of the seismic data really suggests that what we observed was a mine collapse," Benz told Reuters in a telephone interview. "The simplest explanation, based on the seismic observations, was a mine collapse."

The earthquake center detected a tremor with a 3.9 magnitude at 2:48 a.m. MDT (0848 GMT) Monday, centered about 1 mile below the surface, a shallow depth for an earthquake.

Benz said the reasons to suspect that the Crandall Canyon Mine's cave-in was responsible for the seismic activity included the epicenter's proximity to the mine and shallow depth and the nature of the signal itself.

"The character of the seismic signal is not really consistent with what we see in a naturally occurring event (like an earthquake)," Benz told Reuters.

Benz said further modeling would be required because of the complex nature of the signals and that, along with collecting additional data, would take at least several more days and possibly weeks.

The question of whether an earthquake triggered the collapse has become a key issue as rescuers race to reach the six men, who have not been heard from since the mine collapsed early on Monday morning.