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January 28, 2010
Island Park News

ISLAND PARK — The earthquake swarm 19 miles east of here in Yellowstone Park was still occurring on Wednesday, January 27, although not quite as intensely as it has been.

Image: The quakes are at the northeast edge of the ancient caldera outlined here by the red line.

The University of Utah Seismograph Stations reports that a pair of earthquakes of magnitude 3.1 and 3.2 occurred in Yellowstone — the magnitude 3.1 event occurred at 12:52 p.m. on Wednesday, January 27. The magnitude 3.2 occurred on Thursday, January 28 at 1:46 a.m. On Monday this week. the Seismograph Stations reported that a pair of earthquakes of magnitude 3.0 and 3.1 occurred the evening of January 24 in Yellowstone National Park. The first event of magnitude 3.0 occurred at 11:09 p.m. and was followed by a magnitude 3.1 event at 11:21 p.m. Both shocks were located around 9 miles southeast of West Yellowstone and about 10 miles northwest of Old Faithful.

These two earthquakes are part of the ongoing swarm in Yellowstone that began January 17. The largest earthquake in the swarm as of 4 p. m. January 27, had a magnitude 3.8. There have been 1,271 earthquakes in the swarm of magnitude 0.5 to 3.8. This includes 11 events of magnitude larger than 3, with 97 events of magnitude 2 to 3, and 1,163 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 Earthquake swarms are relatively common in Yellowstone.

Scientists at the Yellowstone Volcano Observatory say swarm events are likely the result of slip on pre-existing faults and are called tectonic earthquakes, They are not thought to be caused by underground movement of magma. They say currently there is no indication of premonitory volcanic or hydrothermal activity, but ongoing observations and analyses will continue to evaluate these different sources.

The Yellowstone Volcano Observatory (YVO) is a partnership of the U.S. Geological Survey (USGS), Yellowstone National Park, and University of Utah to strengthen the long-term monitoring of volcanic and earthquake unrest in the Yellowstone National Park region. Yellowstone is the site of the largest and most diverse collection of natural thermal features in the world and the first National Park. YVO is one of the five USGS Volcano Observatories that monitor volcanoes within the United States for science and public safety.