` As seismologists , we 're as certain as we can be that the seismic event registered as a magnitude-3.9 shock was due to the collapse of the mine and not a naturally occurring earthquake , '' said Walter Arabasz , director of the university 's Utah Seismograph Stations , in a written statement . Feds : Violations by the mine 's operator led to 2007 explosions that killed six . Bad design , improper mining led to the mine collapse , feds charged . Mine operator fined more than $ 1.5 million .
Feds : Violations by the mine 's operator led to 2007 explosions that killed six . Bad design , improper mining led to the mine collapse , feds charged . Mine operator fined more than $ 1.5 million .