![Liquefaction at Niigata](https://upload.wikimedia.org/wikipedia/commons/4/42/Liquefaction_at_Niigata.JPG)
The Wasatch Fault is an
active fault
An active fault is a fault that is likely to become the source of another earthquake sometime in the future. Geologists commonly consider faults to be active if there has been movement observed or evidence of seismic activity during the last 10,0 ...
located primarily on the western edge of the
Wasatch Mountains
The Wasatch Range ( ) or Wasatch Mountains is a mountain range in the western United States that runs about from the Utah-Idaho border south to central Utah. It is the western edge of the greater Rocky Mountains, and the eastern edge of the G ...
in the
U.S.
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
states of
Utah
Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...
and
Idaho
Idaho ( ) is a state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Montana and Wyom ...
. The fault is about long, stretching from southern Idaho, through northern Utah, before terminating in central Utah near the town of
Fayette. The fault is made up of ten segments, five of which are considered active.
On average the segments are approximately long, each of which can independently produce earthquakes as powerful as local magnitude 7.5. The five active segments from north to south are called the
Brigham City Fault Segment, the
Weber
Weber (, or ; German: ) is a surname of German origin, derived from the noun meaning " weaver". In some cases, following migration to English-speaking countries, it has been anglicised to the English surname 'Webber' or even 'Weaver'.
Notable pe ...
Fault Segment, the
Salt Lake City
Salt Lake City (often shortened to Salt Lake and abbreviated as SLC) is the Capital (political), capital and List of cities and towns in Utah, most populous city of Utah, United States. It is the county seat, seat of Salt Lake County, Utah, Sal ...
Fault Segment, the
Provo Fault Segment and the
Nephi Fault Segment.
The Wasatch Fault is a
normal Normal(s) or The Normal(s) may refer to:
Film and television
* ''Normal'' (2003 film), starring Jessica Lange and Tom Wilkinson
* ''Normal'' (2007 film), starring Carrie-Anne Moss, Kevin Zegers, Callum Keith Rennie, and Andrew Airlie
* ''Norma ...
(vertical motion) fault which forms the eastern boundary of the
Basin and Range
Basin and range topography is characterized by alternating parallel mountain ranges and valleys. It is a result of crustal extension due to mantle upwelling, gravitational collapse, crustal thickening, or relaxation of confining stresses. The e ...
geologic province which comprises the geographic
Great Basin
The Great Basin is the largest area of contiguous endorheic basin, endorheic watersheds, those with no outlets, in North America. It spans nearly all of Nevada, much of Utah, and portions of California, Idaho, Oregon, Wyoming, and Baja California ...
. The Wasatch Mountains have been uplifted and tilted to the east by movement of the fault.
The average vertical displacement rate of the fault over its history is approximately 0.8–1.2 mm/yr.
Geological history
During the past 10,000 years, major earthquakes (magnitude 7.0 or greater) occur about every 900–1,300 years along any one of the five central segments of the Wasatch Fault. However, the average time-span between earthquakes along the entirety of the central segments is about 300 years. The segment that underlies
Salt Lake City
Salt Lake City (often shortened to Salt Lake and abbreviated as SLC) is the Capital (political), capital and List of cities and towns in Utah, most populous city of Utah, United States. It is the county seat, seat of Salt Lake County, Utah, Sal ...
produced a major earthquake approximately 1,200–1,300 years ago, the
Weber
Weber (, or ; German: ) is a surname of German origin, derived from the noun meaning " weaver". In some cases, following migration to English-speaking countries, it has been anglicised to the English surname 'Webber' or even 'Weaver'.
Notable pe ...
,
Provo, and
Nephi segments each produced one about 200–700 years ago and the
Brigham City fault segment has not produced a major earthquake in about 2,200–2,800 years.
[
]
Earthquake assessment
Statistically, the Wasatch Fault is overdue for another major earthquake. Experts have given a 57% probability of an earthquake magnitude 6.0 or greater occurring within the next 50 years. However, statistical frequency does not necessarily imply periodic behavior, though it can serve as a good indicator. Liquefaction
In materials science, liquefaction is a process that generates a liquid from a solid or a gas or that generates a non-liquid phase which behaves in accordance with fluid dynamics.
It occurs both naturally and artificially. As an example of the ...
due to a strong earthquake is of particular concern because many highly populated areas along the Wasatch Front
The Wasatch Front is a metropolitan region in the north-central part of the U.S. state of Utah. It consists of a chain of contiguous cities and towns stretched along the Wasatch Range from approximately Provo in the south to Logan in the north ...
lie on soft lake sediments, remnants of Lake Bonneville
Lake Bonneville was the largest Late Pleistocene paleolake in the Great Basin of western North America. It was a pluvial lake that formed in response to an increase in precipitation and a decrease in evaporation as a result of cooler temperature ...
.
A strong earthquake on the Wasatch Fault could trigger landslides, cause mass liquefaction, and flooding of low-lying areas forming near lakes due to subsidence
Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope move ...
and tilting. The quake may also rupture the surface causing displacement of up to , and severely damage gas, electric, water, communication, and transportation lifelines. A report released by Bob Carey of Utah's Office of Emergency Services and published by the ''Deseret News
The ''Deseret News'' () is the oldest continuously operating publication in the American west. Its multi-platform products feature journalism and commentary across the fields of politics, culture, family life, faith, sports, and entertainment. Th ...
'' in April 2006 predicts that a strong earthquake occurring in Salt Lake City could kill up to 6,200 people, injure 90,000, and cause US$40 billion in economic losses. Due to the earthquake danger not being well known when many structures were built in the area, at least 42% of the buildings along the Wasatch Front are at risk of moderate to severe damage in the event of a strong earthquake. Many buildings, such as hospitals and schools, are located directly atop the Wasatch Fault. Approximately 50% of hospital beds in Salt Lake City are at risk. Currently, about 80% of Utah's population live along the Wasatch Fault, representing the largest earthquake threat in the interior Western U.S.
On the west end of Salt Lake Valley is another fault zone called the West Valley fault zone that spans 9 miles (16 km) north-northwest. Recent trench studies have shown that the West Valley fault tends to rupture simultaneously with the Wasatch Fault, compounding issues such as liquefaction, landslides and flooding. The two faults likely converge into a single fault deep underneath Salt Lake Valley. On March 18, 2020, a 5.7 magnitude earthquake occurred just north of Magna, causing moderate damage. In March 2021, a new study based on evaluations of the 2020 earthquake and aftershocks determined that the Wasatch Fault undercuts the Salt Lake Valley at a shallower depth than previously thought. This means that a large earthquake on the Salt Lake section of the Wasatch Fault would likely cause more ground shaking and greater damage than previously expected.
Public awareness
As awareness has increased since the 1980s, many key structures in the region have been undergoing extensive seismic retrofitting
Seismic retrofitting is the modification of existing built environment, structures to make them more resistant to seismology, seismic activity, ground motion, or soil failure due to earthquakes. With better understanding of seismic demand on stru ...
, reservoirs on the fault have been drained, and development in at-risk areas curtailed
The Utah Earthquake Program
(a partnership between The Utah Geological Survey
The Utah Geological Survey is based in Salt Lake City, Utah, United States. It also has an office in Cedar City, Utah.
It is a division of the , University of Utah
The University of Utah (U of U, UofU, or simply The U) is a public research university in Salt Lake City, Utah. It is the flagship institution of the Utah System of Higher Education. The university was established in 1850 as the University of De ...
Seismograph Stations, and Utah Division of Emergency Management) has been actively working to educate communities in Utah, conduct research, and investigate technologies that can mitigate the damage caused by a strong earthquake along the Wasatch Fault. Salt Lake City is currently utilizing federal grant funds to run a ''Fix the Bricks'' program targeting seismic safety upgrades in unreinforced masonry buildings.
References
USGS factsheet
External links
Utah Geological Survey Public Information Series 40: The Wasatch Fault
Utah Geological Survey presentation about the fault
Utah Geological Survey Quaternary Fault and Fold Database
Salt Lake City Emergency Management
{{DEFAULTSORT:Wasatch Fault
Geology of Utah
Geology of Idaho
Seismic faults of the United States
Wasatch Front