The United States sits atop some of the most seismically active real estate on Earth. From the plate-boundary faults of California and the Pacific Northwest to the ancient structures of the eastern seaboard, fault lines crisscross the nation in a complex web that reflects hundreds of millions of years of tectonic activity. The USGS locates approximately 20,000 earthquakes per year across the country — roughly 55 per day — though the vast majority are too small for anyone to feel.
Understanding where these faults are, how they behave, and what risk they pose is foundational to earthquake preparedness. This guide provides a comprehensive overview of every major fault system in the United States, explains how to determine whether you live near a fault, and links to detailed pages on the most significant individual fault systems.
Whether you're researching a specific fault line near your home, studying U.S. seismic hazards for professional purposes, or simply want to understand the geological forces shaping the American landscape, this is the starting point.
What Is a Fault Line?
A fault is a fracture in the Earth's crust along which blocks of rock have moved relative to each other. When stress in the crust exceeds the frictional strength of a fault, the fault slips and releases energy in the form of seismic waves — an earthquake.
Not all faults produce earthquakes. Many faults are ancient structures that have been inactive for millions of years. Seismologists focus on faults that show evidence of geologically recent movement, which the USGS defines as movement within the Quaternary period (approximately the last 1.6 million years). These are the faults most likely to produce future earthquakes.
For an in-depth explanation of the physical processes that generate earthquakes, see What Causes Earthquakes.
Types of Faults
Faults are classified by the direction of movement along the fracture surface. The three primary types are:
Strike-Slip Faults
On a strike-slip fault, blocks of rock slide horizontally past each other. The fault surface is approximately vertical. Strike-slip faults are further divided into right-lateral (the block on the opposite side moves to the right) and left-lateral (opposite side moves left). The San Andreas Fault is the most famous right-lateral strike-slip fault in the world.
Strike-slip faults tend to produce strong horizontal shaking and are associated with elongated rupture zones. They are common at transform plate boundaries, where tectonic plates slide past one another.
Normal Faults
On a normal fault, the block above the fault surface (the "hanging wall") moves downward relative to the block below (the "footwall"). Normal faults occur in extensional tectonic settings — where the crust is being pulled apart. The Wasatch Fault in Utah and the Basin and Range faults of Nevada are prominent examples.
Normal faults create distinctive topography: the down-dropped block forms a valley (graben), while the uplifted block becomes a mountain front. The dramatic escarpment of the Wasatch Range rising above Salt Lake City is a direct product of normal faulting.
Reverse (Thrust) Faults
On a reverse fault, the hanging wall moves upward relative to the footwall, driven by compressive forces. When the fault surface is at a low angle (less than approximately 45 degrees), the structure is called a thrust fault. The Cascadia Subduction Zone is a megathrust fault where the oceanic Juan de Fuca Plate is being pushed beneath the North American Plate.
Thrust faults are responsible for some of the world's largest earthquakes. The 1960 Valdivia, Chile earthquake (M9.5) — the largest recorded earthquake in history — occurred on a subduction zone thrust fault, as did the 2011 Tohoku earthquake (M9.1) in Japan. In the U.S., the Cascadia Subduction Zone is the most significant thrust fault.
Table: Fault Types Compared
| Characteristic | Strike-Slip | Normal | Reverse/Thrust |
|---|---|---|---|
| Motion | Horizontal (lateral) | Hanging wall down | Hanging wall up |
| Stress regime | Shear (transform) | Extensional | Compressional |
| Fault plane angle | Near vertical | Typically 45–60° | Variable; thrusts < 45° |
| U.S. examples | San Andreas, Hayward, San Jacinto | Wasatch, Basin and Range faults | Cascadia, Puente Hills Thrust |
| Typical max magnitude | M7–8 | M6.5–7.5 | M8–9+ (subduction) |
| Topographic signature | Offset streams, ridges | Mountain front/valley | Mountain uplift, folding |
The USGS Quaternary Fault and Fold Database
The most comprehensive catalog of U.S. fault lines is the USGS Quaternary Fault and Fold Database. This database documents more than 2,000 faults and folds that show evidence of movement during the Quaternary period (approximately the last 1.6 million years).
For each fault, the database provides:
- Fault name and location: Geographic coordinates and mapped trace
- Fault type: Strike-slip, normal, reverse, or other
- Slip rate: How fast the fault is moving (ranging from less than 0.2 mm/yr to more than 5 mm/yr)
- Age of most recent activity: Categorized by geological time period
- Paleoseismic data: Information from trenching studies, where available
The database is searchable by state, fault name, slip rate, and other parameters. It powers the USGS Interactive Fault Map, which allows anyone to view fault locations relative to their home, workplace, or community.
How to Find Faults Near You
To determine whether you live near an active fault:
- USGS Interactive Fault Map: Visit the Quaternary Fault and Fold Database and use the interactive map to search by location.
- State geological surveys: Many states publish detailed fault maps and seismic hazard assessments. California's California Geological Survey, Utah's Utah Geological Survey, and Oregon's Oregon Department of Geology are among the most comprehensive.
- USGS Seismic Hazard Maps: The National Seismic Hazard Maps show the probability and intensity of ground shaking across the U.S., regardless of whether a specific fault has been mapped.
- Local planning departments: In many seismically active areas, local governments maintain fault zone maps that influence building codes and land-use decisions.
Earthquake Risk Assessment Tool can help you evaluate the seismic hazard for your specific location.
[MAP: United States map showing all major fault lines from the USGS Quaternary Fault and Fold Database, overlaid with seismic hazard zones from the National Seismic Hazard Model. Color-coded by slip rate category: red (>5 mm/yr), orange (1–5 mm/yr), yellow (0.2–1 mm/yr), green (<0.2 mm/yr).] Data source: USGS Quaternary Fault and Fold Database, 2023 National Seismic Hazard Model. Features: All cataloged Quaternary faults, seismic hazard shading (probability of exceeding 0.1g in 50 years), state boundaries, major cities, labeled major fault systems.
High-Risk Seismic Regions of the United States
California
California is the most seismically active of the contiguous 48 states, with thousands of earthquakes detected annually. The state sits astride the Pacific–North American plate boundary, which accommodates approximately 50 mm/year of relative motion. This motion is distributed across multiple fault systems, including the San Andreas, San Jacinto, Hayward, Elsinore, and numerous smaller faults.
The Third Uniform California Earthquake Rupture Forecast (UCERF3) estimates a 93% probability of at least one M6.7+ earthquake in Southern California between 2014 and 2043, and a 72% probability in the San Francisco Bay Area over the same period.
California Earthquake History and Risk
Pacific Northwest
The Cascadia Subduction Zone, stretching from northern California to British Columbia, is capable of producing M9+ megathrust earthquakes. The last such event, the M~9.0 earthquake of January 26, 1700, generated a devastating tsunami that struck both the Pacific Northwest coast and Japan. Research published by the USGS estimates approximately a 7–15% probability of a M9+ Cascadia earthquake in the next 50 years.
Alaska
Alaska is the most seismically active state overall. It has produced three of the ten largest earthquakes recorded worldwide, including the 1964 M9.2 Great Alaska Earthquake — the second-largest earthquake ever recorded. Alaska's seismicity is driven by the subduction of the Pacific Plate beneath the North American Plate along the Aleutian Trench.
Intermountain West
The Basin and Range Province, stretching from Utah to Nevada and into parts of adjacent states, is characterized by extensional tectonics and numerous normal faults. The Wasatch Fault in Utah is the most prominent, running approximately 350 km along the base of the Wasatch Range directly through Salt Lake City, Provo, and Ogden.
New Madrid Seismic Zone
The New Madrid Seismic Zone, centered in southeastern Missouri and extending into adjacent states, produced a series of three M7–7.5 earthquakes during the winter of 1811–1812 — among the largest earthquakes in U.S. history. The zone remains seismically active, with hundreds of small earthquakes detected annually.
South Carolina (Charleston Seismic Zone)
The Charleston area experienced a devastating M~7.0 earthquake in 1886 that killed approximately 60 people and caused widespread damage. The Charleston seismic zone remains active at a low level, and the 1886 event demonstrates that large, damaging earthquakes can occur in the eastern United States.
Hawaii
Hawaii's seismicity is driven by volcanic activity rather than tectonic plate boundaries. The Big Island experiences thousands of earthquakes annually, most related to magma movement beneath Kilauea and Mauna Loa volcanoes. The largest recent event was the 2018 M6.9 earthquake associated with Kilauea's lower East Rift Zone eruption.
Major U.S. Fault Lines: Detailed Profiles
San Andreas Fault
The San Andreas Fault is the most recognized fault in the world. Extending approximately 1,300 km from the Salton Sea to Cape Mendocino, it forms the primary boundary between the Pacific and North American tectonic plates. The fault accommodates roughly 20–28 mm/year of right-lateral slip, depending on the segment.
The San Andreas has produced two of California's most devastating earthquakes: the 1857 M7.9 Fort Tejon earthquake (which ruptured approximately 350 km of the southern and central segments) and the 1906 M7.9 San Francisco earthquake (which ruptured approximately 477 km of the northern segment and killed an estimated 3,000 people). UCERF3 estimates approximately a 59% probability of a M6.7+ earthquake on the southern San Andreas Fault within the 30-year period from 2014 to 2043.
The San Andreas is divided into three major sections: the creeping central section (which releases strain through continuous slow movement), the locked northern section (last major rupture: 1906), and the locked southern section (last major rupture: 1857). The southern section is of particular concern because it has not produced a great earthquake in over 165 years, despite accumulating strain at approximately 25 mm/year.
Read the full San Andreas Fault guide
Cascadia Subduction Zone
The Cascadia Subduction Zone extends approximately 1,000 km from Cape Mendocino, California to Vancouver Island, British Columbia. It is a megathrust fault where the Juan de Fuca Plate subducts beneath the North American Plate at a rate of approximately 30–40 mm/year.
The Cascadia is capable of producing M9+ earthquakes with accompanying tsunamis. Paleoseismic research — particularly tree-ring and coastal subsidence studies — has identified at least 19 M8.7–9.2 earthquakes over the past 10,000 years, with an average recurrence interval of roughly 500 years for full-margin ruptures. The last such event occurred on January 26, 1700. Cities at risk include Seattle, Portland, Eugene, and virtually every coastal community from northern California to British Columbia.
Read the full Cascadia Subduction Zone guide
Hayward Fault
The Hayward Fault runs approximately 74 km through the heavily urbanized East Bay of the San Francisco Bay Area, from San Pablo Bay through Oakland, Hayward, and Fremont to the south. It has been called by the USGS the single most dangerous fault in the United States based on the combination of high earthquake probability and dense urban exposure.
The Hayward Fault has a slip rate of approximately 9 mm/year and last ruptured in the 1868 M6.8 earthquake, which devastated the then-small communities of the East Bay and was called "the Great San Francisco Earthquake" until the 1906 event. UCERF3 estimates approximately a 33% probability of a M6.7+ earthquake on the Hayward Fault by 2043. More than 2.4 million people live directly along the fault trace.
Read the full Hayward Fault guide
San Jacinto Fault
The San Jacinto Fault is the most seismically active fault in California, producing more M3+ earthquakes per year than any other fault in the state. It extends approximately 210 km from San Gorgonio Pass southeast to the Mexican border, running parallel to and east of the southern San Andreas Fault.
With a slip rate of approximately 12–15 mm/year, the San Jacinto has produced multiple M6+ earthquakes in the historical record, including the 1918 M6.8 San Jacinto earthquake. Paleoseismic evidence indicates the fault is capable of M7+ events. The Anza seismic gap — a 50 km section that has not ruptured in over 200 years — is one of the most closely monitored fault segments in the world. Major cities at risk include San Bernardino, Riverside, Hemet, and Temecula.
Read the full San Jacinto Fault guide
Wasatch Fault
The Wasatch Fault extends approximately 350 km along the western base of the Wasatch Range in Utah, passing directly through the state's most populated corridor: Salt Lake City, Provo, Ogden, and surrounding communities. Approximately 80% of Utah's population lives within 25 km of the fault.
The Wasatch is a normal fault with a slip rate of approximately 1–2 mm/year. Paleoseismic studies have identified approximately 24 large surface-rupturing earthquakes on various segments over the past 7,000 years, with the most recent occurring approximately 1,000 years ago on the central segments. The Utah Geological Survey and USGS estimate the Wasatch is capable of producing M7.0–7.5 earthquakes, with a recurrence interval of roughly 1,000–1,300 years for individual segments.
New Madrid Seismic Zone
The New Madrid Seismic Zone is not a single fault but a complex zone of buried faults in the central Mississippi River valley. During the winter of 1811–1812, this zone produced a sequence of at least three M7+ earthquakes (estimated M7.0–7.5) that rank among the largest in U.S. history. The events caused the Mississippi River to temporarily run backward, created Reelfoot Lake in Tennessee, and were felt as far away as the East Coast.
The New Madrid zone remains active. The USGS estimates a 25–40% probability of a M6.0+ earthquake and a 7–10% probability of a M7.5–8.0 earthquake in the New Madrid region within the next 50 years (though these estimates are subject to significant uncertainty and ongoing scientific debate). The zone underlies parts of Missouri, Arkansas, Tennessee, Kentucky, Illinois, Indiana, and Mississippi.
Read the full New Madrid Seismic Zone guide
Ramapo Fault
The Ramapo Fault is a roughly 300 km fault system in New Jersey, New York, and Pennsylvania — the most significant seismic feature in the northeastern United States. The fault passes within approximately 40 km of Manhattan, placing it in close proximity to the nation's largest metropolitan area.
The Ramapo is an ancient structure reactivated under modern tectonic stresses. Its seismicity rate is very low compared to western U.S. faults, but the 2024 M4.8 New Jersey earthquake — felt by an estimated 42 million people — demonstrated the outsized impact that even moderate events can have in this densely populated, seismically unprepared region. The 1884 M~5.2 earthquake near New York City remains the largest known historical event in the area.
Read the full Ramapo Fault guide
Ring of Fire
The Ring of Fire is not a single fault but a roughly 40,000 km horseshoe-shaped zone of tectonic plate boundaries encircling the Pacific Ocean. Approximately 81% of the world's largest earthquakes and about 75% of the world's volcanic eruptions occur along the Ring of Fire. Alaska and the Pacific Northwest are the U.S. regions most directly situated on the Ring.
Read the full Ring of Fire guide
Tectonic Plates
For a comprehensive overview of how Earth's tectonic plates create fault lines and drive earthquake activity worldwide, see Tectonic Plates: The Complete Guide.
Additional Notable U.S. Faults
Several additional fault systems in the United States warrant attention, though they may not yet have dedicated detailed pages.
Denali Fault (Alaska)
The Denali Fault is a major right-lateral strike-slip fault extending approximately 2,000 km across interior Alaska. It produced the 2002 M7.9 Denali Fault earthquake — the largest strike-slip earthquake in North America in nearly 150 years. The event ruptured approximately 340 km of the fault surface and was felt across most of Alaska. Despite the large magnitude, the remote location of the rupture resulted in no deaths and relatively limited structural damage.
Newport-Inglewood Fault (California)
The Newport-Inglewood Fault runs approximately 75 km through the densely populated Los Angeles Basin, from Culver City through Inglewood, Signal Hill, and south to Newport Beach. It produced the 1933 M6.4 Long Beach earthquake, which killed 120 people and led directly to the passage of California's Field Act — the state's first mandatory seismic building code for schools.
The fault passes directly beneath some of the most densely populated neighborhoods in Southern California, including parts of the city of Inglewood and the areas surrounding SoFi Stadium. Its proximity to major population centers makes it one of the most consequential faults in the Los Angeles region.
Puente Hills Thrust Fault (California)
The Puente Hills Thrust is a blind thrust fault (one that does not reach the surface) beneath the Los Angeles metropolitan area. Discovered in the 1990s, it extends approximately 40 km beneath downtown Los Angeles, the San Gabriel Valley, and surrounding communities. SCEC research has estimated that a M7.0+ earthquake on the Puente Hills Thrust could be among the most costly natural disasters in U.S. history, producing intense shaking directly beneath the urban core.
The 1987 M5.9 Whittier Narrows earthquake occurred on the western portion of the Puente Hills system and caused approximately $360 million in damage.
Cheraw Fault (Colorado)
The Cheraw Fault in southeastern Colorado is one of the few well-documented active faults on the Great Plains. Paleoseismic studies have identified at least three surface-rupturing earthquakes in the past 25,000 years, with estimated magnitudes of M6.5–7.0. The fault extends approximately 46 km and has a very low slip rate (approximately 0.1 mm/yr), resulting in very long recurrence intervals (approximately 8,000–14,000 years).
Meers Fault (Oklahoma)
The Meers Fault in southwestern Oklahoma is one of the very few faults in the central United States with visible surface expression — a clear fault scarp approximately 26 km long. Paleoseismic evidence indicates at least two surface-rupturing earthquakes within the past several thousand years, with estimated magnitudes of approximately M6.5–7.0.
The Meers Fault is distinct from the recent surge of induced seismicity (earthquakes triggered by wastewater injection from oil and gas operations) that has affected central Oklahoma since approximately 2009. The induced earthquakes occur on different faults and at different depths.
Charleston Seismic Zone (South Carolina)
The August 31, 1886 Charleston earthquake — estimated at approximately M7.0 — remains the most damaging earthquake in the history of the eastern United States outside the New Madrid zone. The event killed approximately 60 people, destroyed or severely damaged roughly 2,000 buildings, and was felt across most of the eastern United States.
The specific fault responsible for the 1886 earthquake has never been definitively identified, though research has proposed several candidate structures. The area continues to produce occasional small earthquakes, and the USGS seismic hazard maps account for the possibility of future large events in the Charleston area.
Seattle Fault (Washington)
The Seattle Fault is a series of east-west trending reverse faults that pass directly through the city of Seattle. Research published in Science by Atwater and Moore (1992) identified evidence of a M7+ earthquake on the Seattle Fault approximately 1,100 years ago (around 900–930 CE) that produced both significant ground deformation and a tsunami in Puget Sound.
The Seattle Fault is of particular concern because it passes directly beneath Seattle's urban core, including the waterfront, downtown, and several major infrastructure corridors. A repeat of the ~1,100-year-ago event would have catastrophic consequences for the modern city.
Major U.S. Fault Lines: Summary Table
| Fault/Zone | Type | Length | Slip Rate | Last Major Event | Max Credible Magnitude | Population at Risk (approx.) |
|---|---|---|---|---|---|---|
| San Andreas | Strike-slip | ~1,300 km | 20–28 mm/yr | 1906 M7.9 (N); 1857 M7.9 (S) | M8.0+ | ~10 million+ |
| Cascadia Subduction Zone | Megathrust | ~1,000 km | 30–40 mm/yr | 1700 M~9.0 | M9.0+ | ~10 million |
| Hayward | Strike-slip | ~74 km | ~9 mm/yr | 1868 M6.8 | M7.0+ | ~2.4 million |
| San Jacinto | Strike-slip | ~210 km | 12–15 mm/yr | 1918 M6.8 | M7.5 | ~2+ million |
| Wasatch | Normal | ~350 km | 1–2 mm/yr | ~1,000 years ago | M7.5 | ~2 million |
| New Madrid Zone | Complex | ~250 km zone | <1 mm/yr | 1811–12 M7.0–7.5 | M7.5–8.0 | ~3 million |
| Ramapo | Complex/ancient | ~300 km | <0.1 mm/yr | 1884 M~5.2 | M6.0–6.5 | ~20 million (metro) |
| Denali (AK) | Strike-slip | ~2,000 km | 8–12 mm/yr | 2002 M7.9 | M8.0 | Low (remote) |
| Newport-Inglewood (CA) | Strike-slip | ~75 km | ~1 mm/yr | 1933 M6.4 | M7.0+ | ~3 million |
| Puente Hills Thrust (CA) | Blind thrust | ~40 km | 0.5–2 mm/yr | 1987 M5.9 (partial) | M7.0+ | ~4+ million |
| Seattle Fault (WA) | Reverse | ~70 km | ~1 mm/yr | ~900 CE M7+ | M7.0+ | ~4 million (metro) |
| Charleston Zone (SC) | Unknown | Diffuse zone | Unknown | 1886 M~7.0 | M7.0+ | ~800,000 |
[CHART: Horizontal bar chart — Annual Slip Rates of Major U.S. Faults] Data: Cascadia: 30–40 mm/yr; San Andreas: 20–28 mm/yr; San Jacinto: 12–15 mm/yr; Denali: 8–12 mm/yr; Hayward: ~9 mm/yr; Wasatch: 1–2 mm/yr; Newport-Inglewood: ~1 mm/yr; Seattle: ~1 mm/yr; New Madrid: <1 mm/yr; Ramapo: <0.1 mm/yr. Source: USGS Quaternary Fault and Fold Database.
Understanding Seismic Hazard vs. Seismic Risk
Two terms that are frequently confused deserve clarification:
Seismic hazard refers to the probability and intensity of earthquake shaking at a given location. It is a property of the geology. California and Alaska have the highest seismic hazard in the United States.
Seismic risk is the potential for loss — deaths, injuries, property damage, economic disruption. Risk depends on hazard, but also on exposure (how many people and structures are in the area) and vulnerability (how resistant those people and structures are to earthquake shaking).
A location with moderate hazard but very high exposure and vulnerability — such as New York City near the Ramapo Fault, or Memphis near the New Madrid Seismic Zone — can have higher seismic risk than a high-hazard location with low exposure (such as remote portions of the Alaska-Aleutian subduction zone). Understanding this distinction is essential for making informed decisions about earthquake preparedness and building standards.
Earthquake Preparedness by Region
No matter which fault system is nearest to you, the fundamental preparedness actions remain the same:
- Know your hazard: Use the USGS seismic hazard maps and the Quaternary Fault Database to understand the earthquake potential for your area.
- Assess your building: Understand whether your home or workplace is vulnerable. Unreinforced masonry, soft-story apartments, and structures on soft soil are highest risk.
- Prepare supplies: Maintain an emergency kit with water, food, medications, and communication tools for at least 72 hours.
- Practice Drop, Cover, and Hold On: This is the recommended protective action during shaking in the United States, per the USGS and FEMA.
- Consider earthquake insurance: Standard homeowner's policies do not cover earthquake damage in most states. Separate earthquake insurance is available through private carriers and, in California, the California Earthquake Authority.
Check your earthquake risk with our risk assessment tool.