Alquist-Priolo Earthquake Fault Zones in Los Angeles: What Buyers and Sellers Need to Know

What is the Alquist-Priolo Earthquake Fault Zone, and does it affect your Los Angeles property?

The Alquist-Priolo Earthquake Fault Zone Act is a California law requiring sellers to disclose when a property falls within a mapped earthquake fault zone. If your Los Angeles property sits within one of these zones, that disclosure appears in the Natural Hazard Disclosure report delivered to buyers. The designation affects new construction and structural additions but does not require existing homeowners to vacate or retrofit. Buyers and sellers both need to understand what the zone actually means before a transaction moves forward.

By Paul Blair | September 26, 2026

When your Natural Hazard Disclosure report comes back and flags an Alquist-Priolo Earthquake Fault Zone, the instinct is to panic. Don't.

The Alquist-Priolo designation is one of the more misunderstood items in a California real estate transaction. It shows up in the NHD, it sounds ominous, and many buyers treat it like a deal-killer. But the designation doesn't mean the house is sitting on a fault trace ready to rupture. It means the property is close enough to a mapped active fault that California law requires disclosure and, in some cases, a geological study before new construction can happen.

Here's what you actually need to know.

The Alquist-Priolo Act: Where It Came From and What It Requires

California passed the Alquist-Priolo Earthquake Fault Zone Act in 1972, the year after the 1971 Sylmar earthquake killed 65 people and collapsed a hospital. The legislature's goal was straightforward: stop people from building new homes directly on top of active fault traces.

The law assigned the California Geological Survey (CGS) to map special studies zones around active surface fault traces. "Active" in this context means the fault has ruptured in the last 11,000 years. CGS draws a zone extending roughly 50 feet on each side of the mapped fault trace. Any parcel that intersects that zone gets flagged.

What the zone requires depends on what you're trying to do with the property:

• Sell an existing home: You must disclose the designation in the Natural Hazard Disclosure report. That's it.
• Build new construction or add habitable space: A licensed California engineering geologist must confirm no active fault trace runs beneath the proposed structure before permits can be issued.
• Maintain an existing home: No action required. The Alquist-Priolo Act does not require retrofits, inspections, or evacuation for existing structures.

This distinction matters. A buyer purchasing an existing home in an Alquist-Priolo zone is buying a house that was already allowed to be there. The restriction applies to new surface development, not to the house already standing on the lot.

Which Los Angeles Neighborhoods Are Affected?

Los Angeles sits over a dense network of faults. Several are mapped as Alquist-Priolo zones, and the list includes some of the city's most desirable neighborhoods.

The Hollywood Fault is one of the most significant for residential real estate. It runs through the base of the Hollywood Hills from the Los Feliz area westward, passing through parts of West Hollywood and into Beverly Hills. CGS has updated and expanded the Hollywood Fault zone maps in recent years, which means some parcels that previously weren't flagged now are. If you're buying or selling in the Hollywood Hills, the Cahuenga Pass area, or the base of the hills near Franklin Avenue, this fault zone is worth understanding before you go into contract.

The Santa Monica Fault runs roughly east-west, paralleling Wilshire Boulevard from downtown toward the coast. Parts of West Hollywood, Beverly Hills, and the Miracle Mile area sit within or near its mapped zone.

The Malibu Coast Fault affects coastal parcels in Malibu. The Palos Verdes Fault runs along the coast of the Palos Verdes Peninsula. The Newport-Inglewood Fault Zone runs through the South Bay and Culver City corridor.

The Elysian Park fault is often discussed in earthquake risk conversations about Los Angeles. It's a blind thrust fault, meaning it doesn't break the surface. Because of that, it's not mapped under the Alquist-Priolo Act. The same is true for the Puente Hills fault system, one of the faults seismologists watch most closely for potential major Los Angeles earthquake scenarios. Both carry significant seismic risk, but neither triggers an Alquist-Priolo disclosure because they don't reach the surface.

To find out whether a specific property is in an Alquist-Priolo zone, your NHD report will tell you. You can also search the CGS Fault Activity Map by parcel address before making an offer.

If you're buying in the Hollywood Hills, Los Feliz, or anywhere near a mapped fault corridor and want to know what the NHD report is likely to show before you write an offer, reach out. Walking buyers through disclosures before we go into contract is part of how I work.

What It Means for Buyers

Getting an Alquist-Priolo disclosure in your NHD is not a reason to walk away from a house you otherwise want.

What it does mean is that you should read the NHD report carefully and understand what you're being told. The disclosure is binary: the parcel either intersects the mapped zone or it doesn't. It doesn't tell you how close you are to the fault trace, or whether the active trace runs under the house versus under the backyard or the street.

If you want to know more, you have options. A licensed California engineering geologist can review the CGS maps and the parcel's relationship to the fault trace. For existing homes, this isn't required for the purchase, but buyers with significant concerns can commission one.

The bigger practical question for most buyers in a fault zone is about future construction. If you're planning to build an ADU, add habitable square footage, or substantially expand the structure, your permit will trigger a geological investigation requirement before the City of LA or the county will approve it. If the geologist determines an active fault trace runs beneath the proposed footprint, you'll need to redesign around it. For lots where the house already occupies most of the buildable area, this can limit your expansion options in ways worth knowing before you close.

For financing, most conventional lenders don't treat an Alquist-Priolo designation as a dealbreaker on an existing structure. The house was permitted and built, and the lender's collateral question is about current value. Some jumbo lenders may request additional documentation; your lender is the right person to ask directly.

Earthquake insurance is a separate conversation entirely. CEA policies and private earthquake coverage are worth evaluating for any Los Angeles home, regardless of whether it's in an Alquist-Priolo zone.

What It Means for Sellers

If your property is in an Alquist-Priolo zone, your NHD company will flag it in the Natural Hazard Disclosure report. You don't need to do anything extra to comply beyond delivering that report to the buyer within the required timeframe.

California law requires NHD delivery before close of escrow. Buyers have three days after delivery to rescind if they received the report before signing, or five days if it was delivered after signing. This is the same rescission window that applies to all NHD hazards.

What you want to avoid is being surprised. If you're listing in the Hollywood Hills, West Hollywood, or along any of the fault corridors above, order your NHD report early. Know before your buyer does. That way you can factor it into your listing conversation, your pricing, and your disclosure packet.

One thing worth flagging: the CGS has been updating fault zone maps, and some recent updates have expanded existing zones. Properties that weren't in a fault zone when the seller originally purchased them may now be. The NHD company pulls from the current CGS maps, not the maps from when you bought. If your property is near a mapped fault, confirm the current designation before you list.

Selling in Hollywood Hills, Los Feliz, or the Santa Monica corridor? The disclosure picture is part of what I walk sellers through before we go to market. Get your home value estimate and we can talk through the full picture.

Frequently Asked Questions

Does an Alquist-Priolo designation affect my home's value?

The designation alone doesn't automatically reduce value, but it can affect a buyer's decision-making and their comfort level with future construction limitations. Homes in established neighborhoods inside fault zones transact regularly in Los Angeles, and buyers familiar with how the disclosure works are not typically deterred by it. Where value can be affected is when the fault zone limits ADU construction or significant additions that buyers were planning.

Can I build an ADU on a property in an Alquist-Priolo zone?

Possibly, but the permitting process will require a geological investigation. A licensed California engineering geologist will evaluate whether any active fault trace runs beneath the proposed structure's footprint. If the trace avoids the proposed building site, you may be cleared to proceed. If it runs beneath where you planned to build, you'll need to redesign around it. The investigation typically costs $3,000 to $8,000 depending on scope and site conditions.

How do I find out if a specific property is in a fault zone before making an offer?

You can check the California Geological Survey's Fault Activity Map online by address before writing an offer. The official determination in an escrow context comes from the NHD report ordered through escrow, which uses the same CGS data. If you want to know informally before going into contract, I can often provide that from the CGS map or from prior NHD history on properties in the same corridor.

Does the Alquist-Priolo disclosure cover all earthquake risks in Los Angeles?

No. The Alquist-Priolo Act covers only properties within the mapped zone of an active surface fault trace. Seismic hazard more broadly, including liquefaction and landslide risk, is covered by a separate NHD category called Seismic Hazard Zones. Some of the faults most capable of causing a major Los Angeles earthquake, including the Elysian Park and Puente Hills faults, are blind faults that don't reach the surface, so they don't trigger an Alquist-Priolo designation at all.

What happens if CGS expands the fault zone map after I've already purchased?

A map expansion affects future NHD reports and future construction approvals. It doesn't retroactively change your existing home's permit status or require you to take any action as an existing homeowner. If you sell the property after a map expansion, the new NHD report will reflect the current designation, and that's what your buyer will receive.

Alquist-Priolo disclosures come up regularly in Hollywood Hills, Los Feliz, West Hollywood, and along the fault corridors threading through the city. Most transactions involving fault-zone properties close without complications. What matters is understanding the designation before you make a decision, not after.

If you're buying in a fault-zone neighborhood and want to think through what the NHD is likely to show, or if you're selling and want to understand your disclosure picture before you list, I'm happy to walk through it with you.

For sellers: Get your home value estimate For buyers and anyone with questions: Contact Paul Blair

About Paul Blair Paul Blair is the founder and broker of Grey Square, a virtual real estate brokerage representing buyers and sellers across Dallas and Los Angeles. With 22 years in the business and more than $200 million in closed transactions, Paul works the full range of the market, from luxury homes in the Park Cities and Preston Hollow to estates in the Hollywood Hills and across the Westside. Connect with Paul and the Grey Square team at greysq.com. TX TREC #9011505 · CA DRE #01792671.