Utah Fault Lines

Why Utah Has So Many Faults

Western Utah is part of the Basin and Range, where the Earth's crust is being stretched east to west. As it thins, the crust breaks into blocks along faults. Mountain blocks, such as the Wasatch Range, rise while the valley blocks beside them drop. Most of Utah's active faults are this kind, called normal faults, and the steep fronts of its ranges are their work.

The earthquakes that come with this stretching follow a band called the Intermountain Seismic Belt. It runs more than 800 miles from Arizona to Montana, up to 120 miles wide, straight down the spine of Utah and through the Wasatch Front, where most Utahns live. The Wasatch Fault marks the eastern edge of the Basin and Range in northern Utah.

Which Utah Faults Matter Most?

Utah has 211 known Quaternary faults and fault sections: faults that have produced large earthquakes, about magnitude 6.5 or bigger, in the last 2.6 million years. The ones that matter most are those that have moved in the last 10,000 years or so, the Holocene. Only 33 of the 211 had been studied in trenches by 2022, so many remain poorly known.

The Utah Geological Survey names the Wasatch Fault, the Hurricane fault and the Needles fault zone in Canyonlands National Park among the most active. It estimates that a large earthquake strikes about once every 120 years somewhere on the faults of the Wasatch Front region, and once every 5,000 to 20,000 years or more on each of Utah's other Holocene faults.

Lengths and dates are compiled values from the USGS Quaternary Fault and Fold Database and Utah Geological Survey studies; dates are estimates, often with wide uncertainty.

Faults Near Utah's Cities

Salt Lake Valley

Two fault systems face each other across the valley. The Salt Lake City segment of the Wasatch Fault runs along the east bench. The West Valley fault zone crosses the west side of the valley floor; its most recent large earthquake was about 400 years ago, and its large earthquakes have come every 800 years on average over the last 2,000 years. It appears to move along with the Wasatch, and the 2020 Magna earthquake showed the link: the mainshock broke a gently sloping part of the Salt Lake City segment deep underground, and its aftershocks concentrated on the West Valley fault zone. Track it on the Salt Lake City earthquake map.

Ogden and Davis County

The Weber segment of the Wasatch Fault runs about 40 miles from North Ogden to North Salt Lake. Offshore to the west, the Great Salt Lake fault zone runs about 103 km (64 miles) beneath the lake in three sections, Promontory, Fremont Island and Antelope Island, and may connect to the Oquirrh fault zone. Its large earthquakes have come every 3,800 to 5,600 years.

Provo and Utah Valley

The Provo section of the Wasatch Fault runs about 59 km (37 miles) through Salt Lake and Utah counties, along the foot of the mountains above Alpine, Orem, Provo and Springville.

Logan and Cache Valley

Faults line both sides of Cache Valley. The East Cache fault zone separates the valley from the Bear River Range; a trench less than a mile south of Logan Canyon dates its central section's last large earthquake to 4,000 to 4,200 years ago, with 9,000 to 11,500 years between them. The West Cache fault zone runs along the west side of the valley into Idaho. The 1962 Cache Valley earthquake damaged homes in Richmond and Logan.

Tooele

The Oquirrh fault zone runs along the western foot of the Oquirrh Mountains in eastern Tooele Valley, with the Southern Oquirrh Mountains fault zone to the south and the Stansbury fault zone on the west side of the Stansbury Mountains. Their large earthquakes are rare, about every 20,000 years on the Oquirrh faults by the best estimate.

St. George and Cedar City

The Hurricane fault runs about 238 km (148 miles) from just east of Cedar City into Arizona, in six sections. The magnitude 5.8 St. George earthquake of 1992 was likely on the Hurricane fault. The Washington fault reaches into the St. George basin from the south, though no clear evidence of a large earthquake in the last 10,000 years has been found on it.

North of the Great Salt Lake

The short Hansel Valley fault produced Utah's only historical surface-faulting earthquake, the magnitude 6.6 of March 12, 1934. The ground broke for about 11 km (7 miles), with up to half a meter (about 20 inches) of vertical offset. More in our guide to Utah earthquake history.

Southern and Eastern Utah

The Sevier fault runs about 250 km (155 miles), with the Toroweap fault, from south of the Grand Canyon to north of Panguitch. In Canyonlands National Park, the Needles fault zone is among the state's most active, though few people live near it.

The Odds of a Big Earthquake on Utah's Faults

The 2016 forecast by the Working Group on Utah Earthquake Probabilities gives the Wasatch Front region a 43% chance of at least one magnitude 6.75 or larger earthquake in the next 50 years, counting all its faults. Split by fault, the Wasatch Fault zone alone has an 18% chance, and the Oquirrh and Great Salt Lake fault zones together about 6%.

The odds are spread across many faults, which is why the region's chance is higher than any single fault's. No one can predict when or where the next one will strike, so the useful step is to know what to do during an earthquake.

How to Check the Faults Near Your Home

The Utah Geological Survey publishes every mapped fault in its Utah Quaternary Fault and Fold Database, an interactive map, and its Utah Geologic Hazards Portal shows fault traces along with other hazards, such as liquefaction. Search for either by name.

Distance to a fault is only part of the picture. Shaking from a large earthquake reaches far beyond the fault itself, and how a home holds up depends on the ground beneath it and how it was built. For a specific property, a site investigation by a qualified professional is the way to know.