Re: Yellowstone Earthquake Update for February 3

Earthquake Update for February 3
Date: February 3, 2010
Contact: Al Nash, 307-344-2015

Press Release
University of Utah Seismograph Stations
Released: February 03, 2010 10AM MST

This release is a continuation of information updates building upon our five previous press releases on the ongoing earthquake swarm on the west side of Yellowstone National Park.

The University of Utah Seismograph Stations reports that a period of increased seismic activity occurred on February 2, 2010 beginning at ~3:30 PM MST. This period of increased activity lasted about 6 hours and included at least 2 events that were reported felt in Yellowstone National Park. The two largest earthquakes during this sequence were magnitude 3.1 and 2.8 that occurred at 7:31 PM and 7:44 PM respectively.

These earthquakes are part of an ongoing swarm in Yellowstone National Park that began January 17, 2010 (1:00 PM MST). The largest earthquake in the swarm as of 7 AM MST, February 03, 2010, has been a magnitude 3.8.

There have been 1,719 located earthquakes in the swarm of magnitude 0.3 to 3.8. This includes 14 events of magnitude larger than 3, with 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 (for felt reports, please visit http://earthquake.usgs.gov/eqcenter/dyfi/). Earthquake swarms are relatively common in Yellowstone.

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.

Seismic information on the earthquake can be viewed at the University of Utah Seismograph Stations: http://www.seis.utah.edu/.

Seismograph recordings from stations of the Yellowstone seismograph network can be viewed online at: http://quake.utah.edu/helicorder/yell_webi.htm.

Anyone who has felt earthquakes in the swarm are encouraged to fill out a form on the USGS Community Felt reports web site: http://earthquake.usgs.gov/eqcenter/dyfi/.

This press release was prepared by the Yellowstone Volcano Observatory partners of the U.S. Geol. Survey, the University of Utah, and the National Park Service: http://volcanoes.usgs.gov/yvo/

The January-February, 2010, earthquake swarm at Yellowstone National Park has diminished in terms of earthquake-occurrence rate and magnitudes. A few small events continue to be recorded each day at the University of Utah Seismograph Stations (UUSS), the YVO partner responsible for earthquake monitoring at Yellowstone National Park. Seismologists cannot state that the swarm has ceased, but the rate of earthquake occurrence in the Madison Plateau area is now at background levels for this area of Yellowstone. As such, UUSS and YVO will cease to issue daily updates unless conditions change.

As of February 8, 2010 14:00 MST, there have been 1799 events recorded by the automatic earthquake system of the University of Utah. Of those, 827 have been verified by seismic analysts and forwarded to the National Earthquake Information Center (NEIC) for incorporation in the permanent listing of earthquakes. Seismologists of the University of Utah will continue to analyze data from the past several weeks to finalize the earthquake information.

The largest events were 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. Other smaller events were also reported as felt.

The earthquakes were on the Madison Plateau along the northwest side of the Yellowstone caldera, in an area where previous swarms had occurred over the past 30 years. Visual observation of landforms and geothermal features by Yellowstone National Park personnel did not show any changes that could be attributed to the earthquakes.

Yellowstone National Park is in a region of active seismicity associated with regional Basin and Range extension of the Western U.S., as well as youthful volcanism of the Yellowstone volcanic field. Pressurization due to crustal magma bodies of the Yellowstone hotspot and associated shallow geothermal reservoirs can also contribute to earthquakes. Scientists will continue to research the origin of these and other Yellowstone earthquakes.

Any new information will be posted to: http://volcanoes.usgs.gov/yvo/activity/index.php

A summary of the swarm and links to additional information can be found at: http://volcanoes.usgs.gov/yvo/publications/2010/10swarm.php

Seismic information on the earthquake can be viewed at the University of Utah Seismograph Stations: http://www.seis.utah.edu/

Seismograph recordings from stations of the Yellowstone seismograph network can be viewed online at: http://quake.utah.edu/helicorder/yell_webi.htm