Fault Line Map of the United States

How to read this fault map

Each colored line is a mapped fault — a fracture in the Earth's crust where rock on either side has moved. The lines come from the U.S. Geological Survey's Quaternary Fault and Fold Database, the national catalog of faults believed to have been active in the last 2.6 million years. This map draws the whole database: all 112,809 mapped fault sections across 2,107 named fault systems, colored by how fast each one moves.

Dark red is the fastest class, more than 5 mm per year — the San Andreas, the Cascadia megathrust offshore of the Pacific Northwest, the Denali fault in Alaska. Red is 1 to 5 mm per year, including much of the Wasatch fault, the San Jacinto zone, and the Newport–Inglewood fault under Los Angeles. Orange and amber are the slower classes, and grey means the USGS has not published a measured rate for that section at all. Click any line to see its name and slip rate, then jump straight to a full seismic risk report for that exact spot.

A slow fault is not a safe fault

Slip rate is how fast strain accumulates, which sets how often a fault ruptures — not how hard. In the Basin and Range province, which covers Nevada, western Utah, and parts of Idaho, Oregon, Arizona and California, most range-front normal faults slip well under 1 mm per year and are still capable of magnitude 6.5–7.5 surface-rupturing earthquakes. The 1983 Borah Peak earthquake (Mw 6.9) broke the Lost River fault zone, which the USGS rates at under 0.2 mm/yr, and the 1954 Fairview Peak–Dixie Valley sequence in Nevada (Ms 7.2, Mw ~7.1–7.3) came off faults in the 0.1–0.5 mm/yr range. The main exception runs the other way: the central Wasatch segments move at 1.1–2.0 mm/yr, which is fast for the province.

Until 19 August 2026 this map showed only sections slipping at least 1 mm per year. That threshold quietly deleted most of the Intermountain West: in Utah it kept 380 of 4,681 mapped sections, and it left the West Valley fault zone — an intrabasin fault antithetic to the Wasatch, whose Granger and Taylorsville traces run beneath west-central Salt Lake Valley under tens of thousands of homes — off the map entirely, because all fourteen of its mapped sections are classed below 1 mm per year. The Utah Geological Survey wrote to tell us so, and they were right. The threshold is gone.

Why some famous faults don't appear as lines

The most important seismic zone in the central United States — the New Madrid Seismic Zone, source of the violent 1811–1812 earthquakes — does not show up as a bold line here. That is not an omission: New Madrid's faults are buried thousands of feet beneath the sediment of the Mississippi embayment and have almost no expression at the surface, so the USGS does not map them as continuous Quaternary fault traces. Earthquakes do not require a visible fault line at the surface. Large parts of the eastern U.S. carry real seismic hazard from faults that have never broken the ground in a way geologists can map.

The reverse is also true: parts of the West are dense with mapped Quaternary faults, and at a national zoom level they crowd together. That density is real, and it is the reason the old version filtered: a threshold makes a cleaner picture by leaving hazard off it. Zoom in and the individual traces separate.

Check the faults near you

Click any fault on the map, or enter an address above, to generate a free seismic risk report: peak ground acceleration, seismic design category, the nearest mapped faults, and recent earthquakes within 100 km. You can also browse by state for geological background and notable historic earthquakes.

About this data

Fault geometry is sourced from the USGS Quaternary Fault and Fold Database of the United States (National Database layer), which compiles mapping contributed by state geological surveys. Faults are colored by their documented slip rate, and every slip-rate class is drawn, including sections with no measured rate.

Traces here are simplified to about 400 m of tolerance so the whole national database can load in a browser in one request. On phones the same traces ship in a lighter encoding — sections that meet end-to-end drawn as one line, coordinates rounded to about 100 m — every fault, same picture. All of it is a display compromise, not the mapped geometry: real traces are more detailed and more sinuous than the lines drawn here. For engineering, surveying, permitting, or legal use, go to the source — the USGS database above, or your state survey's own portal, which serves the geometry at the resolution it was mapped. In Utah that is the Utah Geologic Hazards Portal.

State surveys also update their fault mapping faster than it propagates into the national USGS compilation, so for any given state the authoritative and most current version is the state survey's own. This map is for informational purposes only and is not a substitute for a site-specific geotechnical or seismic hazard assessment.