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Re: Building on Fault Lines

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In California, building in proximity to an active fault is based on a state law know as the "Alquist-Priolo Earthquake Fault Zoning Act" (California Public Resources Code, Division 2, Chapter 7.5).  The complete Act can also be found in Appendix A of the downloadable publication at the following link (California Geological Survey website):
The State Geologist is required to publish maps delineating the active fault zones which may be on the order of 1/4 mile wide.  For example, the Hayward Fault zone runnig along the east side of San Francisco Bay has varying widths and sometimes multiple fault traces.  One area I'm familiar with has a water tunnel (the San Pablo Tunnel in Kensington, CA, just north of Berkeley) which is bisected by two active traces of the Hayward fault about 600 feet apart (the two traces are believed to intersect at depth).
Even with the fault zones delineated, there are some significant exceptions. Some single family residences are exempt, renovations are sometimes exempt. In 1991, the Oakland-Berkeley Hills Fire destroyed a number of homes on the Hayward Fault.  The Act contains special exemptions to allow homes to be rebuilt. You can find the exemptions near the start of the Act at the above link.  The Alquist-Priolo Act applies to what are defined as "projects".  The exemptions basically define what is or is not a project. The Act went into effect March 7, 1973 and has been amended several times over the years.  The Act requires enforcement by cities and counties as part of their building permit process.
This is probably more detailed than you were looking for but I hope it helps.
Bill Cain, S.E.
Berkeley CA
-----Original Message-----
From: GSKWY(--nospam--at)
To: seaint(--nospam--at)
Sent: Tue, 18 Apr 2006 08:25:46 EDT
Subject: Building on Fault Lines

What restrictions do California (and other states) have as far as building near fault zones?

I.e.  is there a minimum required distance through the nominal fault line?

Is there a restriction on the type of construction within a certain distance of the fault line?  I.e. you can't build a nuclear reactor on top of a known fault line?

When did restrictions start going into place?

When existing buildings are renovated / converted does there distance to a fault line become an issue?

What document / code are there requirements/restrictions contained in?

At what level of government (city / county / state) is this type of restriction promulgated?

Gail Kelley