More than 30 small quakes have struck just during the last week, said Ken Smith, seismic network manager for the Nevada Seismological Lab.
Most of the quakes occurred 18 miles or more below the surface, and are so minor – the largest was about magnitude 1.8 – that Smith thinks they have little chance of being felt at the surface.
Seismologists can’t say with certainty what is happening, but it appears the quakes are being caused by moving magma.
These quakes appear similar to the swarm of quakes that struck under Lake Tahoe in 2003, which were later determined likely to be deep magma injection, Smith said.
Thanks to Wanda for this link