US Earthquake Faults and Folds Map: Interactive USGS Quaternary Fault Viewer

This interactive map displays known earthquake faults and fault zones across the United States, using data from the USGS Earthquake Hazards Program Quaternary Fault and Fold Database. Fault lines are color-coded by age of last activity, giving an immediate sense of which faults have been most recently active. Shaded zones show broader fault areas where the fault zone is wide or poorly constrained. Use the Fault Type filter to focus on strike-slip, normal, or reverse faults, and the Zoom to dropdown to navigate to major seismic regions.

How to Use This Map

Filtering by Fault Type

Use the Fault Type dropdown to filter the map to a specific type of fault movement: strike-slip (lateral sliding), normal (extensional, crust pulling apart), or reverse and thrust (compressional, crust being pushed together). Selecting All Faults shows the complete dataset.

Reading the Age Colors

Each fault line and shaded zone is colored by the age of its most recent known activity. Red and orange faults have been active most recently and represent the greatest potential seismic hazard. Blue faults are older but still considered geologically active within the last 1.6 million years. The legend in the bottom-right corner shows the full color key.

Zooming to a Region

Use the Zoom to dropdown to jump directly to major seismic regions, including California, the Pacific Northwest, the Basin and Range province, Alaska, the New Madrid Seismic Zone, and the Appalachians.

Clicking a Fault

Click any fault line or shaded zone to open a popup showing the fault name, age of last activity, slip sense, slip rate in millimeters per year, total fault length, and a direct link to the USGS Quaternary Fault Database entry for that fault.

Understanding Fault Age and Earthquake Hazard

The USGS Quaternary Fault and Fold Database contains faults that show geological evidence of movement during the past 1.6 million years. Within this dataset, faults are classified by how recently they were last active:

• Historic / Holocene (<15 ka) – Faults active within the past 15,000 years, including faults that have ruptured in recorded history. These represent the highest potential seismic hazard.
• Latest Pleistocene (<130 ka) – Faults active within the past 130,000 years. Still considered capable of generating significant earthquakes.
• Late Quaternary (<750 ka) – Faults active within the past 750,000 years. Lower but non-negligible hazard.
• Quaternary (<1.6 Ma) – Faults active sometime in the past 1.6 million years. Oldest category in the database; uncertainty is higher for both recurrence interval and location.

Major Fault Systems in the United States

The United States contains several major fault systems spanning different tectonic settings:

• San Andreas Fault System (California) – A right-lateral strike-slip fault system marking the boundary between the Pacific and North American plates. One of the most studied and hazardous faults in the world, running approximately 800 miles through California.
• Cascadia Subduction Zone (Pacific Northwest) – A thrust fault where the Juan de Fuca Plate slides beneath the North American Plate. Capable of generating megathrust earthquakes of magnitude 9+, with the last great rupture occurring in 1700.
• Basin and Range Province (Nevada, Utah, Arizona) – A region of normal faulting caused by crustal extension, producing numerous active fault scarps and fault-bounded mountain ranges.
• Wasatch Fault (Utah) – A major normal fault system running through the populated Wasatch Front, capable of producing magnitude 7+ earthquakes.
• New Madrid Seismic Zone (Central US) – An ancient rift system beneath the Mississippi Valley that produced some of the largest historical earthquakes in North America in 1811-1812.
• Ramapo Fault Zone (Appalachians / Mid-Atlantic) – One of the most significant fault zones in the eastern US, running through New York, New Jersey, and Pennsylvania.

About the USGS Quaternary Fault Database

The data displayed in this map comes from the USGS Quaternary Fault and Fold Database, maintained by the USGS Earthquake Hazards Program. The database contains information on faults and associated folds that demonstrate geological evidence of coseismic surface deformation in large earthquakes during the past 1.6 million years. It is the primary authoritative source for fault data used in the USGS National Seismic Hazard Models.

The dataset is published as a public feature service by ESRI and the USGS. Data was last downloaded in April 2025.

Frequently Asked Questions

Does every fault on this map pose an earthquake risk?

All faults in the USGS Quaternary database have produced earthquakes in the geological past and are considered capable of doing so again. However, recurrence intervals vary enormously — some faults rupture every few hundred years, others every tens of thousands of years. The age color coding gives a rough indication of relative activity level.

Why are there so many faults in the western US?

The western US sits near active tectonic plate boundaries and is in a state of ongoing crustal deformation. The Pacific Plate boundary, subduction zones, and the extension of the Basin and Range Province all generate widespread faulting. The eastern US is more tectonically stable, though significant fault zones do exist.

What does fault class A or B mean?

The USGS assigns faults a class rating based on confidence: Class A faults have well-documented evidence of recent activity (historical surface rupture or clear geomorphic expression), while Class B faults have less certain classification based on indirect evidence or limited data.

Are fault areas different from fault lines?

Fault lines represent a mapped trace of a fault at the surface. Fault areas (the shaded zones) represent broader zones where the fault system is distributed, poorly constrained, or where multiple sub-parallel faults occur close together. The shaded zones are especially common in regions with complex, overlapping fault systems.

Does this map include offshore faults?

The map primarily shows onshore faults. The USGS dataset includes some offshore California faults in a separate layer not currently shown in this map. The Cascadia Subduction Zone megathrust, being an offshore feature, also does not appear as a surface fault trace on this map.