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The original item was published from 10/24/2023 2:00:35 PM to 10/24/2023 4:50:47 PM.

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Planning & Economic Development

Posted on: October 23, 2023

[ARCHIVED] State of California Seeks Preliminary Review of Revised Maps of Earthquake Fault Zones

News Flash_Revised Fault Zones

The State Mining and Geology Board has announced an opportunity for residents to provide public comments on the preliminary review maps of revised Alquist-Priolo Earthquake Fault Zones before November 22, 2023.

The State Mining and Geology Board has announced an opportunity for residents to provide public comments on the preliminary review maps of revised Alquist-Priolo Earthquake Fault Zones were released to the City of Santa Rosa and Sonoma County by the California Geological Survey (CGS) on August 24, 2023.

These maps are released under the authority of the Alquist-Priolo Earthquake Fault Zoning (AP) Act that was passed following the 1971 San Fernando earthquake. The AP Act is a state law designed to reduce the hazard from surface fault rupture during an earthquake. More information about the state’s maps can be found on the CGS Preliminary Release web page: conservation.ca.gov/cgs/preliminary-releases

Earthquake Fault Zones are regulatory zones that encompass surface traces of active faults that have a potential for future surface fault rupture. The index maps below (Figure 1) shows the general location of maps delineating the proposed Earthquake Fault Zones within the affected counties.  

Announcement_Preliminary_EFZ_2023_08_24

Figure 1. Index of Preliminary Review Maps of Revised Earthquake Fault Zones issued August 24, 2023.

Comments should be sent to the State Mining and Geology Board before November 22, 2023, and addressed to:  

Jeffrey Schmidt, Executive Officer  

  • State Mining and Geology Board  
  • 710 P Street, MS 1909  
  • Sacramento, CA 95814  
  • [email protected] 

The State Mining and Geology Board will hold a public hearing near the end of the 90-day review period. For more information on the date and location of the public hearing, contact the State Mining and Geology Board.

Additional Information:

FAQs:

What do the revised maps mean for Santa Rosa residents and businesses?

  • The Alquist-Priolo Earthquake Fault Zoning Act requires that the State Geologist delineate earthquake fault zones that encompass all potentially and recently active faults in California that the State Geologist determines to be sufficiently active and well-defined as to constitute a potential hazard to structures from surface faulting or fault creep. 

    The City of Santa Rosa’s Municipal Code requires a 50 foot minimum building setback from the trace of an active or potentially active fault. State code exempts the following project types from meeting this setback requirement: 

    • Residential dwellings (including manufactured homes) on existing parcels 
    • Residential Subdivisions of 4 lots or less


Additional Info...
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