The seismograph stations' data also shows that between Jan. 1 and the Aug. 6 collapse, 28 other seismic events occurred within about two miles of the Crandall Mine.

If, in fact, there were a number of bumps prior to the Aug. 6 accident, Ferriter said that does not necessarily mean mining operations should have been shut down at that time. It would simply tell mine operators they should "be more careful."

"What the bump is is a sign that you are overstressing your pillars as you are extracting materials — the pillars or abutment," Ferriter said. "And when it's in the Utah coal fields, the coal actually compresses the energy. And then when it gets to a certain point, it releases that energy in an explosive manner."

Ferriter said bumps observed in the Crandall Canyon Mine earlier this year prompted managers to stop working the northern section of the mine in March. According to the university's seismograph stations, two seismic events were recorded within about two miles of the mine on March 10, five more occurred March 11 and one took place March 14.

Ferriter said the width of pillars is a "mine-specific thing," and not subject to a standardized width. However, he said the resulting investigation into the Crandall Canyon Mine likely will result in more stringent regulations.

"There will be tighter regulations on the industry and maybe some changes to MSHA (the Mine Safety and Health Administration), too, because they approved the roof-control program" at the mine, he said.

"This is a major disaster, obviously. Congress is looking at it."

And while the end result of the scrutiny and tighter regulations should be increased safety for miners, it also may result in higher prices for coal, he said.

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E-mail: zman@desnews.com