California Alquist-Priolo vs Seismic Hazards Mapping Act

TL;DR

California's two seismic-hazard mapping regimes serve different purposes and require different disclosures. The Alquist-Priolo Earthquake Fault Zoning Act (Public Resources Code §§2621-2630) targets surface fault rupture — the ground literally tearing along a fault trace during an earthquake — and prohibits placing structures for human occupancy across an active fault. The Seismic Hazards Mapping Act (PRC §§2690-2699.6) targets ground behavior during strong shaking: liquefaction, earthquake-induced landslides, and amplified ground motion. Both statutes trigger mandatory seller disclosure through the Natural Hazard Disclosure Statement under Civil Code §1103, but the underlying maps, geologic reports, and building restrictions differ substantially. Understanding which zone a property sits in — and whether one or both apply — is essential to disclosure compliance and buyer risk assessment.

Alquist-Priolo — surface fault rupture only

The Alquist-Priolo Earthquake Fault Zoning Act was enacted in 1972 after the 1971 San Fernando earthquake produced extensive surface fault ruptures that damaged buildings and killed occupants. The Act addresses one specific and narrow hazard: buildings placed directly on the surface trace of an active fault, which can be split or torn during even moderate earthquakes. Ground shaking, landslides, liquefaction, and tsunami are outside AP's scope — they are covered separately by SHMA or other statutes.

Under PRC §2622, the State Geologist delineates Earthquake Fault Zones around the surface traces of active faults. An active fault is one that has ruptured within the Holocene epoch (approximately the last 11,000 years). The zones are typically one-quarter mile wide or less, centered on the mapped fault trace, and vary in precision based on the quality of geological data for each fault. The California Geological Survey publishes zone maps that are provided to cities, counties, and state agencies for planning and permitting purposes, with public notice posted at each county's recorder, assessor, and planning agency offices.

AP disclosure trigger — §2621.9

Public Resources Code §2621.9 imposes the seller disclosure duty for property inside an Alquist-Priolo Earthquake Fault Zone. The duty applies to sellers of real property located within a delineated earthquake fault zone, and to agents acting for such sellers. Disclosure is required when either (a) the seller or agent has actual knowledge that the property is within a delineated zone, or (b) a map has been provided to the city or county under §2622 and public notice of the map's location has been posted at the county's recorder, assessor, and planning agency offices.

The disclosure is made through the Natural Hazard Disclosure Statement under Civil Code §1103.2, which contains a specific line item for Earthquake Fault Zones. In transactions subject to the general real property disclosure duty under Civil Code §1103, the NHD Statement satisfies §2621.9; in transactions using the Local Option Real Estate Transfer Disclosure Statement under Civil Code §1102.6a, that document provides an alternate delivery. A buyer who receives the disclosure late has a rescission right — three days after personal delivery, or five days after delivery by mail or by electronic delivery where electronic delivery is agreed to or authorized — under Civil Code §1103.3.

Seismic Hazards Mapping Act — everything except fault rupture

The Seismic Hazards Mapping Act was enacted in 1990 after the 1989 Loma Prieta earthquake exposed a class of earthquake damage that AP does not cover: catastrophic ground failure through liquefaction, earthquake-induced landslides, and amplified shaking on soft ground. SHMA extends the disclosure and investigation framework to these hazards but through a separate map series and separate statutory citation.

Under PRC §§2695-2696, the State Geologist delineates Seismic Hazard Zones that identify areas susceptible to liquefaction, landslide, and amplified ground shaking during earthquakes. Unlike AP zones which follow the linear traces of faults, SHMA zones cover broader geographical areas — often hundreds or thousands of acres — where the underlying geology creates elevated risk of ground failure during any strong earthquake, regardless of which fault produces the shaking. SHMA zones do not automatically include AP zones — a property can be in an AP zone but not a SHMA zone (built on rock along a fault), in a SHMA zone but not an AP zone (built on unstable soil far from any fault), in both, or in neither.

SHMA disclosure trigger — §2694

Public Resources Code §2694 imposes the parallel seller disclosure duty for property inside a Seismic Hazard Zone. The trigger is again either (a) actual knowledge or (b) map delivery to the local jurisdiction plus public notice posting. Delivery is again through the Natural Hazard Disclosure Statement under Civil Code §1103.2, which contains a separate line item for Seismic Hazard Zones distinct from the AP line item.

The two disclosures appear as separate items on the NHD Statement and must be answered independently. An NHD Statement that discloses AP zone status but says nothing about SHMA status is incomplete if the property is also in a SHMA zone — and vice versa. A seller or agent who has actual knowledge of either designation must disclose it; ignorance is only a defense when neither actual knowledge nor the statutory constructive-notice trigger applies. In practice, professional NHD services (First American, Property I.D., JCP Reports, and similar vendors) generate the disclosure by querying the CGS maps for the specific parcel and populate both line items automatically.

Geologic reports and building restrictions

Beyond disclosure, both statutes create building and permit restrictions that affect development potential and property value. Under AP §2623, cities and counties must require a geologic report before approving any structure for human occupancy within an Earthquake Fault Zone, unless the State Geologist approves waiving the report. The report must show the fault trace does not cross the proposed building envelope, and the standard minimum setback from a known active fault is fifty feet under most local ordinances following AP guidance.

Under SHMA §2697, cities and counties must require a site-specific geotechnical investigation before approving construction in a Seismic Hazard Zone. The investigation must characterize the site's susceptibility to liquefaction, landslide, or amplified shaking and identify mitigation measures if development proceeds. Common mitigations include deep foundations, ground improvement, slope stabilization, or building design that can withstand differential settlement. Both AP and SHMA reports become part of the permanent record and follow the property through subsequent transactions. For related seller-disclosure obligations that appear on the same forms, see our California Natural Hazard Disclosure Statement guide and our Transfer Disclosure Statement guide.

The homeowner's guide requirement for pre-1960 homes

An additional disclosure obligation applies to residential property built before January 1, 1960: the seller must provide the buyer with a copy of the Homeowner's Guide to Earthquake Safety, published by the California Seismic Safety Commission, and must disclose certain known earthquake deficiencies in the structure. This obligation is separate from AP and SHMA disclosure and applies regardless of whether the property is in either zone. The seller's real estate agent must give the seller a copy of the Guide to pass along to the buyer.

The Guide describes common earthquake vulnerabilities in older California housing — unbraced cripple walls, unbolted foundations, unreinforced masonry chimneys, weak parapets, unbraced water heaters — and provides retrofit guidance. Sellers of pre-1960 homes must specifically disclose any known deficiencies in these categories on a supplemental form typically bundled with the NHD Statement. This is a limited-scope disclosure of the seller's actual knowledge, not a required inspection.

Frequently Asked Questions

Can a property be in an AP zone but not a SHMA zone, or vice versa?

Yes. The two zones map different hazards. A property built on stable bedrock along the Hayward Fault might be in an AP zone (surface rupture risk) but not a SHMA zone (no liquefaction or landslide risk on rock). A property on soft bay-margin fill in San Francisco far from any fault might be in a SHMA zone (severe liquefaction risk) but not an AP zone (no fault trace nearby). Many properties in California are in one, both, or neither. The NHD Statement discloses each independently.

Is being in an AP or SHMA zone a deal-killer?

Generally, no. Disclosure is required, and the buyer may need to commission geotechnical investigation before certain construction, but existing homes in zoned areas are common and marketable. AP zones prevent new construction across a fault trace but generally do not prevent purchase, financing, or insurance of existing homes. SHMA zones may increase geotechnical costs for new construction or additions but similarly do not prevent normal sale of existing improvements. Buyers should understand the specific risk profile before proceeding.

Who is responsible for the NHD Statement — seller or agent?

The seller is responsible for the accuracy of the disclosure, but the seller's agent typically arranges for a professional NHD report from a licensed vendor (First American, Property I.D., JCP Reports, etc.) that generates the disclosure based on official map data. The agent has an independent duty of care to ensure the disclosure is complete and accurate. Both seller and agent can be liable for incomplete or inaccurate NHD Statements.

What is the buyer's rescission right if the NHD Statement is delivered late?

Under Civil Code §1103.3, if the NHD Statement or its equivalent is delivered to the buyer after execution of the offer to purchase, the buyer may rescind the offer within three days after personal delivery, or five days after delivery by deposit in the mail or by electronic delivery where electronic delivery is agreed to or authorized. The rescission must be by written notice delivered to the seller or seller's agent. Practical practice is to deliver the NHD Statement as early as possible — often before contract execution — to prevent this rescission window from being triggered.

Does earthquake insurance become mandatory if the property is in an AP or SHMA zone?

No. Unlike FEMA flood zones which can trigger lender-mandated flood insurance, California's AP and SHMA zones do not compel mortgage lenders to require earthquake insurance. Earthquake insurance in California is generally optional and typically purchased through the California Earthquake Authority (CEA) via participating carriers. Being in an AP or SHMA zone does not force insurance but may inform the buyer's decision about whether to purchase coverage.

How can I check whether a specific property is in an AP or SHMA zone?

The California Geological Survey provides an online tool called EQ Zapp (Earthquake Hazards Zone Application) that lets you enter an address and see whether the property sits inside any mapped AP or SHMA zone. Paper maps are also available at county planning departments, the CGS Library, and CGS regional offices in Los Angeles and San Mateo. Professional NHD reports include this information as part of the standard package.

Bottom Line

California operates two distinct seismic-hazard mapping regimes: the Alquist-Priolo Earthquake Fault Zoning Act (PRC §§2621-2630) targeting surface fault rupture, and the Seismic Hazards Mapping Act (PRC §§2690-2699.6) targeting liquefaction, earthquake-induced landslides, and amplified shaking. Both require seller disclosure through the Natural Hazard Disclosure Statement under Civil Code §1103, with the AP disclosure trigger at PRC §2621.9 and the SHMA trigger at PRC §2694. Both statutes also impose geologic-report requirements before new construction. A property can be in either zone, both, or neither, and the disclosures must be answered independently. Buyer rescission rights under Civil Code §1103.3 apply if disclosure is delivered late — three days after personal delivery, or five days after delivery by mail or by electronic delivery where electronic delivery is agreed to or authorized. Pre-1960 homes carry additional Homeowner's Guide to Earthquake Safety disclosure obligations regardless of zone status. For the overall NHD framework, see our California Natural Hazard Disclosure Statement guide. For related seller disclosure obligations that are delivered at the same time, see our Transfer Disclosure Statement guide, and our broker inspection duty guide for how a §2079 visual inspection may surface visible seismic vulnerabilities such as foundation cracks or unbraced cripple walls.

Source: California Public Resources Code §§2621-2630 — Alquist-Priolo Earthquake Fault Zoning Act · California Public Resources Code §§2690-2699.6 — Seismic Hazards Mapping Act · California Geological Survey — Alquist-Priolo Earthquake Fault Zones