An earthquake is a release of energy within the Earth’s crust creating seismic waves that can cause significant damage. Earthquakes are triggered when unexpected movement along a fault occurs, volcanic activity increases, or along the boundaries of tectonic plates. Although ground shaking can occur by many processes, such as volcanic eruptions, the majority of earthquakes are related to movement along faults.
The largest earthquake recorded to date in Wyoming occurred on Aug. 18, 1959 in Yellowstone National Park. The earthquake registered as a magnitude 6.5 and is considered to be an aftershock of the magnitude 7.5 Hebgen Lake earthquake in southwestern Montana.
The WSGS maintains a database and catalog of earthquake events in Wyoming. Below are website links for additional earthquake information.
A fault is a shear fracture or a zone of fractures in the Earth’s crust that show evidence of displacement along blocks of crust. Sudden movement on a fault will release energy causing an earthquake.
Quaternary faults are recognized on the surface that have evidence of movement in the last 1.6 million years and are considered to have the greatest potential to be the sources of future earthquakes. Quaternary faults that show movement during the past 10,000 years are considered active. Approximately 80 Quaternary faults are mapped in Wyoming, with 26 considered active.
Quaternary Faults and Folds in Wyoming
Earthquake activity can be triggered by a number of sources. Volcanic activity, landslides, and movement along a fault are examples of natural causes of earthquakes. In rare instances, anthropogenic (human) influences can also cause an earthquake; these events are referred to as “induced seismicity.” Induced seismicity can potentially be triggered by a variety of industry processes used in the extraction of energy resources, including mine subsidence and blasts, oil and gas field depletions, fluid injection for secondary oil recovery, waste-water disposal, groundwater extraction, and reservoir impoundment.
WSGS hazards geologists completed a study on the potential link between injection/disposal well activities by industry and earthquakes in Wyoming. Computer-based subsurface modeling software allowed geologists to map wells operating between 1984 and 2013 along with recorded earthquake events during the same time period to identify potential relationships. The report can be downloaded here:
Relationships Between Injection and Disposal Well Activities and Known Earthquakes in Wyoming, from 1984 to 2013 (Open File Report 2014-05)
USGS Quaternary Faults and Folds of Wyoming map and database
Interpreting Seismic Records
Seth Wittke (307) 766-2286 Ext. 244