Ronald C. Surdam
Wyoming State Geological Survey
P.O. Box 1347
Laramie, WY 82073
Editor in Chief
307-766-2286, ext. 255
|News Release||January 28, 2010|
More earthquakes felt in Yellowstone
Two earthquakes were felt Jan. 27 and 28 in Yellowstone National Park. They were a continuation of the earthquake swarm that started Jan. 17. No injuries or damage were reported.
The events brought the total number of earthquakes felt to 11, and the seismic activity was ongoing as of 7 a.m. Jan. 28, according to information received by the Wyoming State Geological Survey (WSGS).
The Jan. 27 earthquake occurred at 12:52 p.m. approximately 9 miles southeast of West Yellowstone, Mont., and 19 miles east-northeast of Island Park, Idaho.
The magnitude 2.9, intensity II earthquake occurred 6.2 miles below the surface, according to the U.S. Geological Survey’s National Earthquake Information Center (NEIC) in Golden, Colo.
The second earthquake, magnitude 3.2, happened at 1:46 a.m. Jan. 28 and was felt as intensity II. It occurred 9 miles southeast of West Yellowstone and 18 miles east-northeast of Island Park at a depth of 7.5 miles.
The University of Utah Seismograph Stations (UUSS) reports that there have been approximately 1,500 earthquakes in the swarm, ranging from magnitude 0.5 to 3.8. There have been multiple personal reports of ground shaking from observations inside the park and in surrounding areas for some of the larger events.
UUSS reports that the swarm is likely the result of slip on pre-existing faults rather than underground movement of magma.
An earthquake swarm is a collection of small earthquakes that happen in the same general area and time. Earthquake swarms in Yellowstone do not normally indicate that large, damaging earthquakes are imminent. See http://www.quake.utah.edu/index.shtml for more information about the recent activity in Yellowstone.
The strength of an earthquake at its epicenter is called its magnitude, as measured on the Richter scale. Minor earthquakes – those between magnitude 3 and 3.9 – do not cause structural damage.
The effect of an earthquake on the surface is called its intensity, as measured on the Modified Mercalli Intensity Scale. Intensities range from I (imperceptible shaking) to XII (catastrophic destruction).
The WSGS has compiled seismological characterizations of all Wyoming counties, which include analyses of historic seismicity. See Earthquake Database for more information, or contact Seth Wittke at 307-766-2286, ext. 244, or by e-mail at firstname.lastname@example.org.