Utah Faults

Utah has experienced many earthquakes, large and small, because of its abundance of faults and fault zones. Some of the most active faults in Utah include the Wasatch fault along the Wasatch Front, the Hurricane fault in Southern Utah, and the Needles fault zone in Canyonlands National Park.

Exposing the Wasatch Fault

Past large earthquakes on the central, most active segments of the fault and how geologists interpret evidence of large, prehistoric earthquakes, with footage from the North Creek trench investigation.

North Creek Trench on Wasatch Fault

Time-lapse video of the excavation and investigation of the North Creek trench on the Nephi segment of the Wasatch fault zone.

Wasatch Fault Flyby

The Salt Lake City segment of the Wasatch fault and related geologic features.

Survey Notes: Glad You Asked - Earthquake Early Warning System
Wasatch Front Earthquake Early Warning System

Earthquake early warning (EEW) systems work on the principle that an alert signal can be transmitted almost instantaneously, whereas seismic waves take longer to travel through the Earth’s crust. Sensors detect the first-arriving P wave and trigger the sending of an alert signal, which can give people and automated systems some time to take action before the arrival of stronger S waves and surface waves. This diagram illustrates a conceptual EEW system in the Wasatch Front urban corridor.

Fault Information

What is a fault?

A fault is a break in the earth’s crust along which movement can take place causing an earthquake. In Utah, movement along faults is mostly vertical; mountain blocks (for example, the Wasatch Range) move up relative to the downward movement of valley blocks (for example, the Salt Lake Valley).

Why are faults a concern?

Faults with evidence of Holocene (about 10,000 years ago to present) movement are the main concern because they are most likely to generate future earthquakes. If the earthquake is large enough, surface fault rupture can occur.

What is a surface fault rupture?

With a large earthquake (about magnitude 6.5 and greater), the fault rupture can reach and displace the ground surface, forming a fault scarp (steep break in slope). The resulting fault scarp may be several inches to 20 feet in height, and up to about 40 miles in length, depending on the size of the earthquake.

What are the effects of surface fault rupture?

An area hundreds of feet wide can be affected, called the zone of deformation, which occurs chiefly on the downthrown side of the main fault and encompasses multiple minor faults, cracks, local tilting, and grabens (downdropped blocks between faults). Buildings in the zone of deformation would be damaged, particularly those straddling the main fault.

Also, anything crossing the fault, such as transportation corridors, utilities, and other lifelines, both underground and above ground, can be damaged or broken. The ground can be dropped below the water table on the downdropped side, resulting in localized flooding.

Surface fault rupture can also cause tectonic subsidence, which is the broad, permanent tilting of the valley floor down toward the fault scarp. Tilting can cause flooding along lake and reservoir shorelines nearest the fault; along altered stream courses; and along canals, sewer lines, or other gravity-flow systems where slope gradients are lessened or reversed.

Where and when is surface fault rupture likely to occur?

On the Holocene fault on which a magnitude 6.5 (approximate) or larger earthquake occurs. On average, these earthquakes may occur once every 120 years on various faults in the Wasatch Front region; once every 350 years somewhere along the central part of the Wasatch fault (between Brigham City and Nephi); once every 2,000 years at any specific locality along the central Wasatch fault; and once every 5,000 to 20,000 years or more on other Holocene faults in the state.

What can be done to protect homes?

Faults can be avoided by setting homes back a safe distance. Special-study areas have been delineated along faults where geologic studies are recommended to assess the hazard, locate faults, and recommend setbacks. However, the use of special-study areas in land-use ordinances varies by county and city, as does the level of enforcement.

Therefore, buyers, particularly of older homes (pre-1985), should personally check available fault maps to see if the home is near a fault (within a few hundred feet) and, if so, may want a geological site investigation performed. For newer homes, buyers should check with the county or city to determine whether geologic studies were performed for the site or subdivision and, if so, look at a copy of the geologic report.

Earthquake Articles

Search:
TitleTopicPublished
Investigating Earthquake Hazard on the Southern Wasatch Fault Zone Earthquakes 2019
The Wasatch Fault from Above: Re-mapping the Wasatch Fault Zone Using Airborne High-Resolution Topographic Data Faults 2017
Liquefaction Hazards in Utah Hazards 2016
Paleoseismic Investigation of the Taylorsville Fault, West Valley Fault Zone, Utah Faults 2016
What geologic hazards should I be aware of as a homeowner in Utah? Hazards 2016
Glad You Asked: What is an Earthquake Early Warning System, and does Utah Have One? Earthquakes 2015
Liquefaction in the April 15, 2010, M 4.5 Randolph Earthquake Hazards 2011
Putting down roots in earthquake country – your handbook for earthquakes in Utah, Utah Seismic Safety Commission (pdf) Earthquakes 2008
UGS Responds to the Magnitude 6.0 Wells, Nevada, Earthquake Earthquakes 2008
UGS Excavates New Fault Trenches on the Weber Segment of the Wasatch Fault Zone Faults 2008
Earthquakes – Wasatch Fault Earthquakes 2007
Glad You Asked: I am thinking of buying a house at “X” address… is it near a fault? Faults 2007
Protecting Utah Homes Hazards 2005
Earth Fissures near Beryl Junction in the Escalante Desert Earth Fissures 2005
Earthquake Fault Map of a Portion of Tooele County, Utah Maps 2004
Earthquake Fault Map of a Portion of Washington County, Utah Maps 2004
Improving Our Understanding of Earthquake Hazards in Utah Hazards 2004
The Mapleton Megatrench Hazards 2004
New Guidelines for Evaluating Surface- Fault-Rupture Hazards in Utah Hazards 2004
What are seismic surveys and how much “shaking” do they create? Earthquakes 2004
Maps Show Potential Geologic Effects of a Magnitude 7 Earthquake Hazards 2003
Triggered Seismicity in Utah from the Denali Fault Earthquake Hazards 2003
Ground-Shaking Map for a Magnitude 7.0 Earthquake on the Wasatch Fault Salt Lake City, Utah Metropolitan Area Hazards 2002
Photo essay of four Utah earthquakes, 1921-1972 (pdf) Earthquakes 2001
What is the Grand Staircase? (pdf) Landforms 1999
Earthquakes & Utah (pdf) Earthquakes 1997
Homebuyers guide to earthquake hazards in Utah (pdf) Earthquakes 1996
The Wasatch Fault (pdf) Earthquakes 1996
Earthquake Ground Shaking in Utah Hazards 1994
Earthquake Fault Map of a Portion of Utah County, Utah Maps 1991
Earthquake Fault map of a Portion of Weber County, Utah Maps 1990
Earthquake Fault Map of a Portion of Salt Lake County, Utah Maps 1990
Earthquake hazards and safety in Utah (pdf) Earthquakes 1990
Earthquake Fault Map of a Portion of Davis County, Utah Maps 1989
Landforms Presentation (PowerPoint) Landforms

Earthquake Articles: 35

Earthquake Fault Maps (pdf)

Utah earthquakes (1850–2016) and Quaternary faults (pdf)
Map 277

Earthquake fault map of a portion of Cache County, Utah
Public Information Series #83

Earthquake Fault Map of a portion of Davis County, Utah
Public Information Series #2

Earthquake Fault Map of a portion of Salt Lake County, Utah
Public Information Series #3

Earthquake fault map of a portion of Tooele County, Utah
Public Information Series #84

Earthquake Fault Map of a portion of Utah County, Utah
Public Information Series #11

Earthquake fault map of a portion of Washington County, Utah
Public Information Series #85

Earthquake Fault Map of a portion of Weber County, Utah
Public Information Series #1

Technical geologic-hazard maps organized by county