California Geological Survey

This site answers the question "What is an Earthquake Fault Zone?" and provides a guide for determining if a property lies within an Earthquake Fault Zone. The Natural Hazards Disclosure Act, effective June 1, 1998 (as amended June 9, 1998), requires that sellers of real property and their agents provide prospective buyers with a "Natural Hazard Disclosure Statement" when the property being sold lies within one or more state-mapped hazard areas, including an Earthquake Fault Zone.

Index

What is an Alquist-Priolo Earthquake Fault Zone?

Alquist-Priolo Earthquake Fault Zones are regulatory zones that encompass surface traces of active faults that have a potential for future surface fault rupture. What does it mean to be located within an Earthquake Fault Zone? It means that an active fault is present within the zone and the fault may pose a risk of surface fault rupture to existing or future structures. If property is not developed, a fault study may be required before the parcel can be subdivided or before most structures can be permitted. If a property is developed, the Alquist-Priolo Act requires that all real estate transactions within an Earthquake Fault Zone be disclosed by the seller to prospective buyers.

How does the Act work?

The law requires the State Geologist to establish regulatory zones (known as Earthquake Fault Zones) around the surface traces of active faults and to issue appropriate maps. ["Earthquake Fault Zones" were called "Special Studies Zones" prior to January 1, 1994.] The maps are distributed to all affected cities, counties, and state agencies for their use in planning and controlling new or renewed construction. Local agencies must regulate most development projects within the zones. Projects include all land divisions and most structures for human occupancy. Single family wood-frame and steel-frame dwellings up to two stories not part of a development of four units or more are exempt. However, local agencies can be more restrictive than state law requires.

Before a project can be permitted, cities and counties must require a geologic investigation to demonstrate that proposed buildings will not be constructed across active faults. An evaluation and written report of a specific site must be prepared by a licensed geologist. If an active fault is found, a structure for human occupancy cannot be placed over the trace of the fault and must be set back from the fault (generally 50 feet).

How can I find out if a property is located in an Earthquake Fault Zone?

There are 544 Official Maps of Earthquake Fault Zones statewide. Earthquake Fault Zones are located within the jurisdiction of 36 counties and 100 cities. Counties are required to post notices at the offices of the county assessor, recorder, and planning agency that advise the public of the availability and location of Earthquake Fault Zones that affect that county (Public Resources Code 2621.9c2 ).

The first step in determining if a property is located in an Earthquake Fault Zone (EFZ) is to consult Table 4 listing affected cities and counties. You must know the name of the county where the property is located and whether or not the property lies within the boundaries of an incorporated city.

For a property that is not located in an incorporated city:

For a property that is located in an incorporated city:

Earthquake Fault Zones are relatively narrow zones and will not exist throughout all of the area within an affected city or county. Therefore, if you think a property may be located within an EFZ, you must consult the appropriate Official Map of Earthquake Fault Zones. These maps can be inspected at Public Information Offices of the Department of Conservation, California Geological Survey. The planning agency or building department of the affected city or county also has copies of zone maps located within their jurisdiction. In most cases, it should be obvious whether or not a property is located in an EFZ. Consult the appropriate local lead agency if you are uncertain that a property lies within an EFZ.

How can I be certain that the map I have is an Official Map of Earthquake Fault Zones?

The following text appears on all Alquist-Priolo Earthquake Fault Zone Maps for which disclosure under Public Resources Code Section 2621.9 is required:

STATE OF CALIFORNIA
EARTHQUAKE FAULT ZONES

Delineated in compliance with
Chapter 7.5, Division 2 of the California Public Resources Code
(Alquist-Priolo Earthquake Fault Zoning Act)

OFFICIAL MAP/REVISED OFFICIAL MAP

[Signature of State Geologist releasing map]
STATE GEOLOGIST

Please note that, prior to January 1, 1994, Alquist-Priolo Earthquake Fault Zones were known as "Special Studies Zones." Maps issued prior to June 1, 1995 will have "SPECIAL STUDIES ZONES" in the title block instead of "EARTHQUAKE FAULT ZONES." A notification and labels to be placed on the official maps noting the name change were sent to affected lead agencies in early 1994.

Information on Disclosure Requirements

Effective June 1, 1998, the Natural Hazards Disclosure Act, requires that sellers of real property and their agents provide prospective buyers with a "Natural Hazard Disclosure Statement" when the property being sold lies within one or more state-mapped hazard areas. If a property is located in an Official Earthquake Fault Zone issued by the State Geologist (California Geological Survey), the seller or the seller's agent must disclose this fact to a potential buyers. The law specifies two ways in which this disclosure can be made. One is to use the new Natural Hazards Disclosure Statement as provided in Section 1102.6c of the California Civil Code. The other way is to use the Local Option Real Estate Disclosure Statement as provided in Section 1102.6a of the California Civil Code. The Local Option Real Estate Disclosure Statement can be substituted for the Natural Hazards Disclosure Statement only if the Local Option Statement contains substantially the same information and substantially the same warning as does the Natural Hazards Disclosure Statement.

In addition to Earthquake Fault Zones, information shown on Official Maps of Seismic Hazard Zones and other state and federal maps of natural hazards also must be disclosed. See CERES for links to other web sites that address these disclosure requirements.

Map Availability

Official Maps of Earthquake Fault Zones are issued periodically by the California Department of Conservation, California Geological Survey in compliance with the Alquist-Priolo Earthquake Fault Zoning Act. These maps are available for reference at all California Geological Survey public information offices (listed below) and at offices of cities and counties affected by the zones. Counties are required to post notices at the offices of the county assessor, recorder, and planning agency that advise the public of the availability and location of Earthquake Fault Zones that affect that county (Public Resources Code 2621.9c2). The planning department of each affected city and county has been provided with a reproducible master of each map affecting its jurisdiction. Copies of the zone maps are available for purchase from some of these local agencies. An index map with names of the Official Maps of Earthquake Fault Zones, lists of affected cities and counties, and additional information are provided in Special Publication 42 (see below).

Arrangements have been made with BPS Reprographic Services to provide bond copies of Official Maps of Earthquake Fault Zones. Orders for Earthquake Fault Zones maps should be directed by phone or by mail to:

EACH MAP MUST BE ORDERED BY NAME AS SHOWN ON THE INDEX MAP IN SPECIAL PUBLICATION 42. There is a $7.00 minimum charge per order. Each order will be charged $4.09 for handling regardless of the number and type of maps ordered. Sales tax and shipping charges will be added. The first copy of each map will cost $1.90. Additional copies of the same map are $1.32. Prices are subject to change.

Special Publication 42, "Fault-rupture Hazard Zones in California, is available for $6.00 per copy plus shipping and handling at any California Geological Survey public information office or it may be ordered by mail from CGS, P.O. Box 2980, Sacramento, California 95812. Special Publication 42 is not available from BPS Reprographic Services.

For More Information

For more information on Earthquake Fault Zones and the Alquist-Priolo Act, consult Special Publication 42, Fault-rupture Hazard Zones in California. Special Publication 42 is published by the California Department of Conservation, California Geological Survey. This publication is revised when new Earthquake Fault Zones Maps are issued or when changes are made to the Alquist-Priolo Act. Special Publication 42 contains a detailed index map showing 544 Official Earthquake Fault Zone maps issued by the State Geologist, an explanation of the Alquist-Priolo Act, and a description of the California Geological Survey’s Fault Evaluation and Zoning Program. Also included are technical guidelines for evaluating surface fault rupture hazard (DMG Note 49) and for reviewing geologic reports (DMG Note 41). The most recent edition of Special Publication 42, published in late 1997, is available for $6.00 per copy plus shipping and handling at any California Geological Survey Public Information Office or it may be ordered by mail from CGS, P.O. Box 2980, Sacramento, California 95812.

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