Tsunami Zones in California

A tsunami hazard zone is a coastal area that could be inundated by a tsunami — a series of waves generated by an earthquake, submarine landslide, or other sudden displacement of ocean water. In California, these zones are mapped by the California Geological Survey (CGS) in partnership with Cal OES (the Governor's Office of Emergency Services).

The maps are based on worst-case modeling: they show the maximum extent of flooding from the largest reasonably expected tsunami sources, including both distant earthquakes (such as a Cascadia subduction zone event) and local sources (submarine faults and landslides off the California coast). The zones are designed for evacuation planning and public awareness, not as predictions of frequent events.

• Mapped by: CGS and Cal OES using hydrodynamic modeling of multiple tsunami source scenarios.
• Covers: low-lying coastal areas, harbors, estuaries, and areas along tidal channels that could see tsunami wave inundation.
• Updated: as modeling improves and new geological data refines source parameters — the statewide mapping effort continues to expand.

Tsunami hazard zones exist along the entire California coast, but the highest-risk areas include:

• Crescent City and the North Coast — closest to the Cascadia Subduction Zone and historically California's most tsunami-affected area (the 1964 Alaska tsunami killed 11 people in Crescent City).
• San Francisco Bay and the East Bay shoreline — low-lying fill areas and bayfront neighborhoods sit within mapped zones.
• Santa Cruz and Monterey Bay — harbor areas and beachfront properties are within the mapped inundation zone.
• Southern California harbors — Marina del Rey, Long Beach, Newport Beach, and San Diego harbor areas carry tsunami risk from both distant and local sources.

The zones often extend only a few blocks inland, but in flat, low-lying areas they can reach farther. Elevation is the primary factor — properties above the modeled wave height are outside the zone even if they are near the coast.

Tsunami zones are not one of the six original statutory hazard categories under Civil Code §1103, which predates the statewide tsunami mapping program. However, professional NHD providers increasingly include tsunami zone screening as a supplemental determination because the CGS maps are publicly available and the information is material to buyers of coastal property.

Verity NHD includes tsunami zone screening in every NHD report and flags the result with a plain-English explanation — including whether the zone is based on a local or distant tsunami source. The report also notes the distinction between tsunami zones and dam inundation zones, which are a separate statutory determination despite both involving potential water inundation.