Earthquake swarm in southern Nevada

There's been what looks like an unusual swarm of 40+ earthquakes in southern Nevada, near the Utah border that began yesterday (Jan. 28).     The swarm seems to have begun with a magnitude 4.1 earthquake yesterday morning with dozens of small quakes since then as well as with another, M=4.0 event early last evening.   [Map credit, USGS]

Our colleagues at the Utah Geological Survey blogged about it earlier in the day when there had been about two dozen earthquakes.