Yellowstone Swarm Slows

Yellowstone Earthquake Swarm Summary as of 5 February 2010

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 5. Image by Jamie Farrell
and Robert B. Smith (University of Utah), data from the University of Utah
Seismograph Stations. Click on the image for a full-size version.

The current swarm at Yellowstone National Park has slowed considerably. Yesterday, there were 7 earthquakes recorded by the University of Utah Seismograph Station (UUSS) automatic earthquake system. All were beneath magnitude 2.0. As of February 5, 2010 9:00 AM MST there have been 1,771 earthquakes located. The swarm began January 17, 2010 around 1:00 PM MST about 10 miles (16 km) northwest of the Old Faithful area on the northwestern edge of the Yellowstone Caldera. Swarms have occurred in this area several times over the past two decades.
This swarm has been longer (in time) and with more earthquakes than last year's swarm beneath Yellowstone Lake (December '08/January '09). The total seismic energy released is still somewhat less. The largest recorded swarm at Yellowstone remains the Fall 1985 swarm, which was located in a similar location, in the NW corner of the Yellowstone Caldera.
The current swarm has included 14 events with a magnitude larger than 3, 136 events of magnitude 2.0 to 2.9, 1,098 events with a magnitude of 1.0 to 1.9, and 530 events of magnitude 0.0 to 0.9. The largest events so far have been a pair of earthquakes of magnitude 3.7 and 3.8 that occurred after 11 PM MST on January 20, 2010. Both events were felt throughout the park and in surrounding communities in Wyoming, Montana, and Idaho.
See the University of Utah Seismograph Stations for the most recent earthquake data. Analysts are now working through all the automatic earthquake locations, and are refining hypocenter locations, depths and magnitudes for inclusion in the earthquake catalog. As the events are refined, they are listed on the UUSS website and loaded into the ANSS catalog . Seismograph recordings are also available online by clicking on the station of interest on the Yellowstone seismograph network station map.

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