An earthquake is an abrupt release of energy from strain that has accumulated within the earth’s crust. Earthquakes produce seismic waves that can cause motion of the ground surface and lead to significant damage. Most earthquakes are triggered by movement along subsurface faults or by volcanic activity.

The largest earthquake recorded to date in Wyoming occurred Aug. 18, 1959, in Yellowstone National Park. The earthquake registered as a magnitude 6.3 and is considered to be an aftershock of the magnitude 7.2 Hebgen Lake earthquake in southwestern Montana.

Rock Creek fault
Rock Creek fault, Lincoln County, Wyoming [Credit: Seth Wittke, WSGS]

Quaternary Faults

A fault is a fracture or fracture zone along which blocks of the earth’s crust have been displaced relative to each other. Sudden movement on a fault will release energy causing an earthquake.

To understand patterns of earthquake activity across a longer time interval than the historic record can provide, geologists document and characterize faults that have offset geologically young deposits at the ground surface. These Quaternary faults, so named because they have been active in the last 2.6 million years, can be studied to provide information on when and where large, surface-rupturing earthquakes occurred in the past, and they highlight areas where large earthquakes may occur in the future.

Quaternary Faults and Folds in Wyoming (pdf)

Induced Seismicity

Earthquakes are most commonly triggered by natural sources, such as movement along a fault or volcanic activity. In rare instances, anthropogenic (human) influences can also cause an earthquake; these events are referred to as induced seismicity. Induced seismicity can stem from a variety of activities related to the energy and mining industries, including mine subsidence and blasts, oil and gas field depletions, fluid injection for secondary oil recovery, wastewater disposal, groundwater extraction, and reservoir impoundment.

WSGS hazards geologists completed a study on the potential link between injection/disposal well activities and earthquakes in Wyoming. Subsurface modeling software allowed geologists to map and compare recorded earthquake events and wells operating between 1984 and 2013. The report can be downloaded here:

Helpful Links

USGS Quaternary Faults and Folds of Wyoming Map and Database

Earthquake Preparedness

The WSGS participates in the Great Wyoming ShakeOut drill each October and encourages you to do the same.

Interpreting Seismic Records

Teton Fault scarp
Teton Fault scarp, Teton County, Wyoming [Credit: James Mauch, WSGS].


James Mauch,