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The earthquake was centered about 3 miles southwest of Wayan along the eastern flank of the Grays Range. The focal point was fixed at a depth of 5.0 km below the surface and the fault plane solutions from NEIC and Harvard indicated nearly pure normal-slip (extension motion) along a moderate dipping and generally north-south or north-northeast trending plane. This type of fault motion is common for earthquakes along the eastern margin of the Basin and Range.

Preliminary reports indicate the quake was widely felt in the region and as far away Idaho Falls, Pocatello, Montpelier and Malad City. It was also felt at Teton Village, and Star Valley, Wyoming.

Although we do not have reports from the epicentral area, tectonic action at this magnitude and location may have caused items to topple from tables and shelves, knocked pictures from walls, and cracked some walls. We do not expect any structural damage.

Most people in outlying areas describe the shaking as a mild rumbling of the ground lasting for a few seconds.

It was preceded five minutes earlier (17:13:48 - UTC) by a M3.5 foreshock and there have been a few small aftershocks detected but data has not been processed at this time.

It was the largest earthquake in this area since the February 2, 1994 Draney Peak M5.8 earthquake. That quake was centered about 17 miles to the southeast and caused light to moderate damage in Star Valley, Wyoming. It was followed by a robust aftershock sequence, which lasted for several months and included dozens of M3s and M4s and a few in the M5 range.

Micro- and macroseismic activity is relatively common in southeastern Idaho, consisting mostly of a couple M1s and M2s per week with an occasional moderate jolt. In 1992, a series of light to moderate earthquakes struck the Grays Lake area located slightly north of the 2001 earthquake series. Suzette Jackson of INEL, Idaho National Engineering and Environmental Laboratory, summerizes the Grays Lake series here.

The geology of the region is fascinating and earthquakes have played an important role in its development. See the links below for more information:

Additional Seismic information links:

• Recent Earthquakes in the Intermountain Seismic Belt - UUSS
  • Detail map of the area
• United States Geological Survey - Earthquake Hazards
• Idaho Falls Chamber of Commerce
• Idaho Geological Survey
• Boise State University Geology Department
  • BSU Earthquake Seismology
• Utah Geological Survey
  • Earthquake Hazards
• University of Utah Seismological Stations

Seismograms of the Wayan earthquake from nearby stations:

• Black Mountain, UT- UUSS
• Hansel Valley, UT - UUSS
• Grizzly Peak, UT- UUSS
• Salt Lake City, UT- UUSS
• Old Faithful, Yellowstone Park, WY- UUSS
• Bozman, MT - MBMG

News Reports:

There have been no national wire news reports at this time

Report update: 8:00 a.m., Monday, April 23, 2001