Just as a point of interest, it is my understanding that just as people on the open ocean are oblivious to the passage of a tsunami, people in deep mines often are completely unaware of the occurrence of an earthquake which is felt strongly at the surface. It is my understanding, as an amateur, that this counterintuitive factoid results from the fact that surface waves (the ones contributing the most to motion and damage in an earthquake) are just that - surface waves. They only work their magic at a free surface. And this also explains why mine collapses due to earthquakes are extremely rare.

OTOH, the reported magnitude of the quake in Utah that Skywise reported (now set at somewhat below M4.0) does seem quite large for a rockburst or mine collapse. If the seismic event was entirely a mine collapse/rockburst, then it must certainly have been a big one! And the miners are reported to be 4 miles from the entrance. It doesn't look good for them . . .

MW
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