EarthMapped Fault lines map
Map of the 50 United States with 141,413 km of Quaternary faults drawn as colored lines by age of last movement. Faults crowd California, Nevada, Utah, Oregon and southern Alaska; the eastern states have almost none.

Fault Lines Map

This map shows 141,413 km of US faults that moved in the past 1.6 million years, colored by age, from the USGS Quaternary Fault and Fold Database.

Data source: USGS Quaternary Fault and Fold Database of the United States, Public domain (US Government work). Download: GeoJSON .

Last updated

What the map shows

Each line is a Quaternary fault Quaternary fault. A fault with evidence of surface movement during the Quaternary, the past 1.6 million years, as mapped in the USGS Quaternary Fault and Fold Database. Source : a fault or fold where geologists found evidence that the ground broke or bent at the surface sometime in the past 1.6 million years. The USGS keeps these in its Quaternary Fault and Fold Database, built from thousands of studies, many of them trenches dug across faults to date prehistoric earthquakes. The same database feeds the National Seismic Hazard Model.

Colors show how recently each fault last moved, by the age classes the database uses. Turn a class off with the switches. The lines are simplified for the web; for detailed work, use the USGS files.

Key facts

  1. The USGS database maps 141,413 km of faults and folds in 112,516 line pieces, under 2,134 fault numbers. USGS, Quaternary Fault and Fold Database
  2. Every fault on the map shows geologic evidence of surface movement in the Quaternary, the past 1.6 million years. USGS, Quaternary Fault and Fold Database
  3. California has the most, 42,000 km (30%), then Nevada (26,293 km) and Alaska (15,327 km).
  4. 88% of the length is in the western states from the Rockies to the Pacific. Alaska and Hawaii add 16,393 km.
  5. Normal faults, where one block drops down, make up 52% of the length. Strike-slip faults, which slide sideways, make up 22%; thrust and reverse faults 16%.
  6. The San Andreas fault zone is about 1,300 km long. Along it the Pacific Plate has slid past the North American Plate for 10 million years, at about 5 cm a year. USGS, Understanding plate motions
  7. In 1906 the San Francisco earthquake ruptured a 430 km long segment of the San Andreas. USGS, Plate tectonics and people

Fault length by state

Quaternary faults by state, km of mapped line
StateFault length (km)Share
California 42,000 30%
Nevada 26,293 19%
Alaska 15,327 11%
Oregon 12,064 9%
New Mexico 9,163 6%
Utah 8,919 6%
Washington 5,892 4%
Arizona 4,534 3%
Washington (offshore) 4,401 3%
Wyoming 3,023 2%
Idaho 2,837 2%
Colorado 2,679 2%
Montana 2,208 2%
Hawaii 1,066 1%
Texas 890 1%
Oklahoma 73 0%
Kansas 44 0%

Data source: USGS Quaternary Fault and Fold Database of the United States, Public domain (US Government work).

By age of last movement

Quaternary faults by age class
Age classFault length (km)Share
Historic 10,438 7%
Latest Quaternary 37,219 26%
Late Quaternary 23,546 17%
Middle and late Quaternary 10,545 7%
Undifferentiated Quaternary 50,771 36%
Class B 8,894 6%

The two youngest classes, Historic and latest Quaternary, cover 47,657 km, 34% of the total.

Data source: USGS Quaternary Fault and Fold Database of the United States, Public domain (US Government work).

By type of slip

Normal faults pull the crust apart. Thrust and reverse faults push it together. Strike-slip faults, right lateral or left lateral, move sideways, like the San Andreas, a transform boundary.

Quaternary faults by slip sense
Slip senseFault length (km)Share
Normal 72,981 52%
Right lateral 22,231 16%
Thrust 17,870 13%
Left lateral 5,771 4%
Reverse 5,405 4%
Unspecified 4,844 3%
Strike slip 2,888 2%
Anticline 473 0%
Thrust; Strike slip 260 0%
Syncline 214 0%
Monocline 191 0%
Left lateral; Normal 147 0%

Data source: USGS Quaternary Fault and Fold Database of the United States, Public domain (US Government work).

The world's biggest fault lines: plate boundaries

Outside the US, the longest faults are plate boundaries, where plates spread apart, sink under each other or slide past. The plate boundaries map draws all of them, and the Ring of Fire map shows the band of subduction zones around the Pacific.

Download

us-quaternary-faults.geojson holds the lines on this map, one feature per age class, in longitude and latitude. It is simplified from the USGS Quaternary Fault and Fold Database (2020 files), which is public domain. Lengths on this page are measured on the sphere from the USGS lines.

Related: the earthquake map, the Cascadia subduction zone off the Pacific Northwest, the North American Plate and the plate boundaries map.

Glossary

Quaternary fault
A fault with evidence of surface movement during the Quaternary, the past 1.6 million years, as mapped in the USGS Quaternary Fault and Fold Database. Source
Transform boundary
Plates slide horizontally past each other. Crust is neither made nor destroyed. Source
Epicenter
The point on the surface directly above the focus, the place underground where an earthquake rupture starts. Source
Ring of Fire
The belt of volcanic arcs and ocean trenches that partly rings the Pacific Ocean, where earthquakes and eruptions are frequent. Source

All terms in the glossary

Fault lines map FAQ

Where are the fault lines in the United States?
Mostly in the West. California, Nevada, Alaska, Oregon and Utah hold most of the 141,413 km in the USGS database. The East has very few mapped faults that moved in the past 1.6 million years.
What is the biggest fault line in the US?
The San Andreas fault zone in California, about 1,300 km long. It is the boundary where the Pacific Plate slides past the North American Plate, at about 5 cm a year on average, USGS reports.
Is a fault line the same as a plate boundary?
Not always. A plate boundary is where two plates meet, and it is often made of many faults. Most faults on this map are inside the North American Plate, far from any plate boundary. The plate boundaries map shows the boundaries themselves.
Can earthquakes happen away from fault lines on this map?
Yes. Faults that are buried or not yet found can break, and earthquakes can happen inside plates. The New Madrid earthquakes of 1811-1812 and the 1886 Charleston earthquake happened inside the North American Plate, USGS notes.
What do the colors mean?
They show the age of the most recent movement the database records for each fault, from Historic (youngest) to undifferentiated Quaternary. Class B is a separate class the database uses; we show it in gray.

Sources: USGS, Quaternary Fault and Fold Database; USGS, Understanding plate motions; USGS, Where earthquakes occur.