EARTHQUAKE FAULT ZONE
A Brief Explanation
California law requires a seller (if acting without an agent) or
the seller's agent to disclose to a prospective transferee of real
property if the property is located within a delineated Earthquake
Fault Zone provided that official maps prepared by the
California State Geologist, or the information contained in the
maps, are "reasonably available." Disclosure
must be made if:
a seller (if acting without an
agent) or the seller's agent has "actual knowledge" (Public
Resources Code Section 2621.9(c)(1)) that the property is located
within a delineated earthquake fault zone, OR
the maps or the information
contained in the maps are deemed "reasonably available" if
a map prepared by the California State Geologist pursuant
to Public Resources Code Section 2622 that includes the property
has been provided to the city or county, and a notice
has been posted at the offices of the county recorder,
county assessor, and county planning agency that identifies
the location of the map, the effective date of the notice,
and any information regarding changes to the map received by
The Alquist-Priolo Special Studies
Zones Act of 1972, renamed the "Alquist-Priolo Earthquake
Fault Zoning Act" in 1994 (hereinafter referred to as the "A-P
Act", regulates development and construction of buildings
intended for human occupancy so as to mitigate hazards associated
with fault rupture and/or fault creep.
The A-P Act resulted in the establishment of Earthquake Fault Zones
that span the "surface traces" of delineated active faults.
A surface trace is the mapped location of a fault based on surface
and/or subsurface geologic information.
Residential structures that lie atop the surface trace of an active fault can
be damaged or destroyed by "surface faultrupture",
where quarter mile in width (i.e, the "typical" zone boundaries are
set back approximately 660 feet on either side of the fault trace). Pursuant
to the A-P Act, the State Mining and Geology Board has classified faults either
(a) "Active" (those faults
having surface displacement within about the last 11,000 years), or (b) "Potentially
Active" (those faults having surface displacement during the
last 1.6 million years).
The A-P Act applies to new or renewed
construction and development projects, including all divisions of
land as well as most structures intended for human occupancy. Certain
types of structures and developments are excluded. The exclusion does not excuse
or limit disclosure obligations.
The A-P Act does not prevent cities
and counties from establishing policies and criteria which are stricter
than those established by the State of California. Local Agencies may develop
and enforce stricter standards, charge extra fees related to these standards,
or disallow exemptions otherwise permitted by the State of California (Public
Resources Code, Section 2624).
A property that lies partially or entirely
within a designated Earthquake Fault Zone may be subject to requirements
for site-specific geologic studies before any new or additional construction
may take place. If an active fault is found on a property, structures generally
will not be allowed to be constructed within 50 feet of the fault trace.
Information portrayed on Earthquake
Fault Zone maps is not a sufficient substitute for geologic and geotechnical
site investigations under the A-P Act.
Earthquake Fault Zone maps
pursuant to the A-P Act only depict known active fault zones.
Because a property located outside a mapped Earthquake Fault Zone may
still be subject to the effect of earthquakes, property owners are encouraged
to take appropriate safety and retrofitting measures to minimize potential
Earthquake Fault Zone maps pursuant to the
A-P Act only depict known active fault zones. Because a property
located outside a mapped Earthquake Fault Zone may still be subject to the effect
of earthquakes, property owners are encouraged to take appropriate safety and
retrofitting measures to minimize potential damage.
For more information, please contact the California
Department of Conservation, Division of Mines and Geology in Sacramento,
San Francisco, or Los Angeles, or via the world wide web at http://www.consrv.ca.gov/dmg/index.html.
Earthquake Fault Zone maps may be reviewed at local public works, planning or