A period of increased activity
Posted by JAC on 2/3/2010, 1:27 pm



Map of Yellowstone National Park showing recent swarm earthquakes in red,
previous swarms from 1995-2009 in green, and volcanic vents with yellow
stars. Caldera boundaries are shown in orange. Mallard Lake Resurgent dome,
to the southwest, and Sourcreek Resurgent dome, to the northeast, are shown
with yellow lines. The histogram at the top right shows the number of
earthquakes per day from January 15 to February 3. Image by Jamie Farrell
and Robert B. Smith (University of Utah), data from the University of Utah
Seismograph Stations.


Earthquakes continue to be felt in Yellowstone National Park as part of a recent ongoing swarm that now includes 1,719 quakes.

On Tuesday, Feb. 2, a period of increased seismic activity occurred, staring at 3:30 p.m., according to the University of Utah Seismograph Stations.  This period of increased activity lasted about six hours and included at least two events that were reported felt in Yellowstone National Park.  The two largest earthquakes during this sequence were a magnitude 3.1 quake at 7:31 p.m. and a magnitude 2.8 quake at 7:44 p.m.

These earthquakes are part of an ongoing swarm in the park that started on Jan. 17. The largest earthquake in the swarm as of 7 a.m. Wednesday, Feb. 3 was a magnitude 3.8.

There have been 1,719 located earthquakes in the swarm of magnitude 0.3 to 3.8, including 14 events of magnitude larger than 3, 135 events of magnitude 2 to 3, and 1,570 events of magnitude less than 2.  There have been multiple personal reports of ground shaking from observers inside the park and in surrounding areas for some of the larger events.

Earthquake swarms are relatively common in Yellowstone, according to the park.

"Yellowstone Volcano Observatory scientists still consider that the swarm events are likely the result of slip on pre-existing faults and are not thought to be caused by underground movement of magma. Currently there is no indication of premonitory volcanic or hydrothermal activity, but ongoing observations and analyses will continue to evaluate these different sources," the park said in a news release.



http://www.seis.utah.edu/EQCENTER/PRESS/yell_press.htm#20100203


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Large pickup of Yellowstone Swarm - JAC, 2/2/2010, 10:12 pm
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