Each time an earthquake occurs in Wyoming, the news media and public asks, “Does Wyoming have earthquakes?” Short answer: Yes!
In comparison with California, Nevada, and Utah, major earthquakes here are infrequent. But each year, hundreds of earthquakes do occur in and around Wyoming. Taking steps now to prepare your family and home will help mitigate the effects of moderate to severe earth shaking.
The Great Wyoming ShakeOut is an annual opportunity to practice how to be safer during big earthquakes: "Drop, Cover and Hold On." The ShakeOut has also been organized to encourage you, your community, your school, or your organization to review and update emergency preparedness plans and supplies, and to secure your space in order to prevent damage and injuries.
Learn more below, or read answers to frequently asked questions.
Register today so that you or your organization will:
Earthquakes are common in Wyoming. Historically, earthquakes have been felt in each Wyoming county, with most earthquakes occurring in the western third of the state. The first reported earthquake occurred in Yellowstone National Park in 1871 and the most recent likely occurred there. Yellowstone National Park is one of the more seismically active areas in the United States. In fact, during the third week of January 2010 there was a swarm of more than 1,200 earthquakes with magnitudes between 0.5 and 3.8 in Yellowstone National Park.
A dynamic magma chamber beneath Yellowstone, combined with regional tectonic forces, results in significant seismic activity. Many of Wyoming’s earthquakes are associated with movement within or around the magma chamber. Others are associated with active faults.
Yellowstone is a super-volcano, and explosively erupted 0.64 million, 1.3 million, and 2.1 million years ago. The explosive eruptions led to the formation of giant calderas, the collapse of which led to the formation of faults in the vicinity. In addition, after the major eruptions, resurgent domes formed within the calderas. The doming process led to the formation of other faults.
Faults in Wyoming are capable of generating damaging earthquakes anywhere in the state. Historically, Wyoming earthquakes are tied to faults that are buried. Buried faults are faults that have never broken the surface and are generally considered to be capable of generating up to magnitude 6.5 earthquakes. Since the distribution of buried faults is not well known and many faults remain unmapped in Wyoming, it is assumed that earthquakes up to magnitude 6.5 can occur anywhere in the state.
In 1959 a magnitude 7.5, intensity X earthquake occurred just west of Yellowstone National Park, near Hebgen Lake, Montana. The Hebgen Lake earthquake is a model for the types of earthquakes that can occur in western Wyoming.
Wyoming’s earthquake history spans only 130 years and there are gaps in the record for the late 19th Century and first half of the 20th Century. Even though Wyoming has not experienced an earthquake epicenter with a magnitude 7.5 within its borders in the last 130 years, the potential does exist. After the Hebgen Lake earthquake in 1959, monitoring in Wyoming started to improve. Prior to the 1950s most earthquakes were detected and located by personal reports. After the 1950s, earthquakes were more commonly located by seismometers.
Recent earthquake activity in Wyoming prompted the Wyoming State Geological Survey Office to develop 16 earthquake scenarios. The scenarios include four earthquakes based on data from historic earthquakes occurring near Casper, Gillette, Laramie Peak, and Estes Park, Colorado. The scenarios can be found on line at http://www.wsgs.uwyo.edu/data/gis/ims-projects.aspx.
A detailed description by county of recorded earthquakes in Wyoming can be found on line at www.wrds.uwyo.edu/wrds/wsgs/hazards/quakes/seischar/seischar.html. Following is a table of Wyoming’s ‘Top Ten Recent Earthquakes’ which either caused damage or concern for Wyoming residents, listed in chronological order with the most recent first:
|February 3, 1995||Near Little America||5.3 / V|
|February 3, 1984||Draney Peak Idaho near Star Valley||5.9 / VII|
|November 3, 1984||Atlantic City||5.1 / VI|
|October 18, 1984||Albany County||5.5 / VI|
|June 30, 1975||Yellowstone National Park||6.4 / VII|
|August 17, 1959||Hebgen Lake, just outside Yellowstone National Park||7.5 / X|
|March 26, 1932||Jackson||Unknown / VI|
|June 12, 1930||Near Grover in Star Valley||Estimated 5.8 / VI|
|November 14, 1897||Casper||Unknown / VI-VII|
|November 7, 1882||Bewtween Laramie and Estes Park, Colorado||6.2-6.5 / VII|
Please visit the following links for more information on earthquakes hazards and preparation:
Why is it important to do a Drop, Cover, and Hold On drill? To react quickly you must practice often. You may only have seconds to protect yourself in an earthquake, before strong shaking knocks you down--or drops something on you. Practicing helps you be ready to respond.
Ground shaking during an earthquake is seldom the cause of injury. Most earthquake-related injuries and deaths are caused by collapsing walls and roofs, flying glass and falling objects. It is extremely important for a person to move as little as possible to reach the place of safety he or she has identified because most injuries occur when people try to move more than a short distance during the shaking.
Look around you now, before an earthquake. Identify safe places such as under a sturdy piece of furniture or against an interior wall in your home, office or school so that when the shaking starts you can respond quickly. An immediate response to move to the safe place can save lives. And that safe place should be within a few steps to avoid injury from flying debris.