The intent of the Alquist-Priolo Act is to prohibit the location of developments and structures for human occupancy across the trace of active fault, thus avoiding the hazard of surface fault rupture.

Earthquake Fault Zones encompass hazardous faults, which are defined as those faults that are sufficiently active and well-defined:

       *  Sufficiently active - faults that exhibit evidence of Holocene displacement

         (approximately last 11,000 years)

       *  Well-defined - trace detectable by trained geologist

NOAA Natural Hazards Image Database

1906 San Fransisco Earthquake. M = 8.2

1979 El Centro Earthquake. M = 6.9

1971 San Fernando Earthquake. M = 6.6

NOAA Natural Hazards Image Database

Youd, T.L & Olsen H.W  in Geological Survey Professional Paper 733

ALQUIST-PRIOLO EARTHQUAKE FAULT ZONING ACT