Earthquakes
California earthquake fault zones
A practical first stop for Alquist-Priolo fault zones, seismic hazard zones, disclosure, and local planning-office checks before you buy or build.
A fault-zone map is not a prediction that a home will fall down. It is a regulatory map that says surface fault rupture needs a closer look.
Alquist-Priolo zones are about active fault traces. Seismic hazard zones are a different map family for liquefaction and earthquake-triggered landslides.
The simple rule is to use the state map for a first check, then confirm with the city or county what it means for the exact parcel before buying, building, or remodeling.
First moves
- 1
Use CGS EQ Zapp or official CGS regulatory maps for the parcel.
- 2
Check whether the parcel is in an Alquist-Priolo fault zone or a separate seismic hazard zone.
- 3
If you are buying, review the natural hazard disclosure documents and any reports already on file.
- 4
If you are building, adding, or remodeling, call the local planning or building office before design work gets expensive.
- 5
If the map line is close, use a licensed professional or the local office instead of guessing from a screenshot.
Watch for
- 1
Alquist-Priolo is about surface fault rupture, not shaking intensity, tsunami, fire, or every earthquake risk.
- 2
Seismic hazard zones can raise liquefaction or landslide review even away from an Alquist-Priolo line.
- 3
Map tools are a starting point; local permit files, old geologic reports, and parcel-specific studies can matter.
- 4
Disclosure, insurance, lending, remodel permits, and new construction can each treat the map differently.
Go deeper
Outdoor weather and hazard checks
A last-check guide for weather, smoke, fire, heat, surf, rivers, snow, roads, earthquakes, and the live sources to trust before you leave.
Wildfire defensible space around the home
Start here before clearing plants, moving firewood, changing mulch, or checking whether a home is in a wildfire hazard zone.