New Online Maps Show California Homes On Active Faults

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An Alquist-Priolo Earthquake Fault Zone Maps (California Geological Survey)

An Alquist-Priolo Earthquake Fault Zone Maps (California Geological Survey)

SAN FRANCISCO (KCBS/AP) – Anyone with an Internet connection can now find out whether the house they want to buy is on one of California’s earthquake faults.

The California Geological Survey announced Thursday that it was posting its fault zone maps online for the first time. The 547 maps were previously available only in paper or CD formats.

California state geologist John Parish says the agency uses Google Maps’ address-matching technology to link users to the right map for a property’s location.

The maps compile nearly 40 years worth of data to show which addresses lie on an active fault line, said geologist Bill Bryant.

“It can displace the ground as small as a few centimeters or it can displace the ground as large as maybe 20 feet,” he said.

KCBS’ Barbara Taylor Reports:

The Alquist-Priolo Zoning Act prohibits new construction on active faults and requires disclosure if a property is sold. But a homeowner curious whether a house lies on an active fault typically had to do some legwork.

There are no active fault lines in San Francisco, though they are common in more than half the state.

In the Bay Area, the California Geological Survey has identified active fault lines in Alameda, Contra Costa, Marin and Santa Clara counties.

Bryant cautioned that just because an address is not on or near a fault line does not mean the home is not in danger.

“Typically you’re going to get about 95 percent of damage from a large earthquake from shaking and only about five percent damage due to fault rupture.”

View the searchable Alquist-Priolo Fault Zone Maps on the Website of the California Geological Survey.

(© 2011 CBS Broadcasting Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)

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