Recent Mount Hood earthquake swarm is typical for Oregon volcano.
May 16, 2016
At Mount Hood, a swarm of small earthquakes was detected May 15-16, 2016. Swarms are not uncommon in the Mount Hood area, which typically experiences one or two swarms per year that last for several days to weeks.
The earthquakes in this swarm are located 2-3 miles south of the summit of Mount Hood at depths of 2-3 miles below sea level. The largest event was a magnitude 1.8. Earthquake rates reached as many as 20 earthquakes per hour, peaking between 6-7 am on May 16 before decreasing later in the day. The Pacific Northwest Seismic Network located nearly 40 earthquakes; many more events occurred that were too small to be located.
This swarm is very typical for Mount Hood because it is located several miles away from the summit vent – it is rare to see swarms occur directly beneath the summit. The most energetic swarm recorded to-date occurred in June-July of 2002, which included a magnitude 4.5 that was broadly felt in the Government Camp area. The current swarm is much, much smaller than the 2002 swarm, both in terms of earthquake size and in number.
Studies of past swarms in the Mount Hood area have concluded that they likely are occurring on pre-existing regional faults and are best thought of as regional “tectonic” earthquakes, rather than earthquakes directly linked to magmatic processes. This is in contrast to the recent uptick in seismicity at Mount St. Helens, which we DO believe is caused by magmatic processes (specifically magma recharge).
May 18, 2016.Mont Hood , United States :
Source : CVO