The search for six missing miners was abruptly halted after a second cave-in killed three rescue workers and injured at least six others who were trying to tunnel through rubble to reach them.
The cave-in at 6:39 p.m. was believed to be caused by what seismologists call a “mountain bump,” in which shifting ground forces chunks of rock from the walls. Seismologists say such a bump caused the Aug. 6 cave-in that trapped the six men more than 3 miles inside the central Utah mine.
The force from the bump registered a 1.6 at the University of Utah seismograph stations in Salt Lake City, said university spokesman Lee Siegel. It was the 20th reading at the university since the original collapse, which registered a 3.9 on Aug. 6.
“These events seem to be related to ongoing settling of the rock mass following the main event,” Siegel said Friday morning. “I don’t think I’m going too far to say that this mountain is collapsing in slow motion.”