Earthquake Hazards
Utah has experienced 17 earthquakes greater than magnitude (M) 5.5 since pioneer settlement in 1847, and geologic investigations of our region’s faults indicate a long history of repeated large earthquakes of M 6.5 and greater prior to settlement. Seismic activity can often trigger a succession of additional potentially destructive hazards. The seismic-related hazards listed below all possess their own potential for destruction. Some areas of the state are more susceptible than others when it comes to being at risk.
While Utah is not on a boundary between tectonic plates where most of the world’s earthquakes occur, it is in the tectonically extending western part of the North American plate. Thus, earthquakes in Utah are related to interactions with the Pacific plate along the plate margin on the west coast of the United States. Also, many small earthquakes in east-central Utah are induced by underground coal mining.
Utah Earthquakes Virtual Field Trip from the Natural History Museum of Utah.
View all their virtual field trips here.
Ground Shaking
A sudden motion or trembling of the earth as stored elastic energy is released by fractures and movement of rocks along a fault.
Surface Fault Rupture
Displacement (rupture) of the ground surface along a tectonic fault during an earthquake that often results in a a steep scarp.
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Liquefaction
A sudden, large decrease in shear strength of a saturated sandy soil caused by a temporary increase in soil pore water pressure during an earthquake.
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Landslides and Rockfalls
Landslides and/or rockfalls can be triggered by earthquake ground shaking.
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Tsunamis
A series of waves in the ocean or lake caused by the displacement of a large volume of water. Displacement may be due to underwater fault rupture or landslides into the water.
Seiches
A standing (oscillating) wave in a body of water that is at least partially enclosed and can be induced by earthquakes and other energy sources.
Tectonic Subsidence
The lowering and tilting of a valley floor on the down-dropped side of a fault during an earthquake. This commonly causes localized flooding and gravity flow utility failure.
Quick Clays
Typically marine-type clays that significantly lose strength when subjected to sufficient stress.
Utah Earthquakes (1850 to 2016) and Quaternary Faults Map
This map shows earthquakes known to have occurred within and surrounding Utah from 1850 through December 2016 and mapped Quaternary faults considered to be earthquake sources. The faults shown on the map have been sources of large earthquakes (about magnitude 6.5 or greater) during the Quaternary Period (past 2.6 million years) and are the most likely sources of large earthquakes in the future. Most small to moderate size earthquakes plotted on the map are “background” earthquakes not readily associated with known faults and of a size generally below the threshold of surface faulting (about magnitude 6.5). Buried or unmapped secondary faults are likely sources of much of the background seismicity.
Home damaged by the Springdale landslide caused by the 1992 St. George earthquake.
Costs of Earthquake Hazards
Although only two fatalities (ground shaking-related) from earthquakes have occurred in Utah since 1847, scenario modeling predicts 2000 to 2500 fatalities, 7400 to 9300 life-threatening injuries, 55,400 buildings completely damaged, 21 million tons of debris, and $33.2 billion in estimated short-term, direct economic losses from a major M 7.0 earthquake on the Salt Lake City segment of the Wasatch fault zone. Short-term financial losses and long-term economic costs include damages, cleanup, closed businesses, lower productivity and economic output, and other costs. It is projected that 61% of the total number of buildings in the 12 county area in northern Utah will be moderately damaged or totally destroyed. Such an event will likely take decades to recover from and will be the single most costly geologic hazard event to affect Utah.
Related Information:
Geologic Hazards and Insurance – Are You Covered?
Highlighted Scientific Publications
Circular 122
Guidelines for Investigating Geologic Hazards and Preparing Engineering-Geology Reports, with a Suggested Approach to Geologic-Hazard Ordinances in Utah
Open File Report 667
Earthquake Database for Utah Geological Survey Map 277—Utah Earthquakes (1850–2016) and Quaternary Faults
Public Information Series 100
Liquefaction Hazards in Utah
Special Study 163
Surface Fault Rupture Map - Geologic Hazards of the Tickville Spring Quadrangle, Salt Lake and Utah Counties, Utah
Map 277
Utah Earthquakes (1850-2016) and Quaternary Faults
Data file (zip)
Special Study 162
Geologic Hazards of the Moab Quadrangle, Grand County, Utah
Public Interest Articles
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Earthquake Articles: 53
