SACRAMENTO -- A
Seismic Hazard Zone map covering a
60-square-mile area that extends from
the Los Altos Hill and Cupertino in the
south to the San Francisco Bay
shorelines becomes official Friday. The
map impacts local planners, developers,
property sellers and real estate agents.
If property is
located in a zone of required
investigation, where liquefaction or
landslides could occur during a large
earthquake, the local building
department must require geologic studies
before projects are issued permits.
Also, property sellers and real estate
agents must inform potential buyers if
property they're selling is in a Seismic
Hazard Zone, as is the case when
property is in a designated flood or
The Seismic Hazard
Zone map for the 60-square-mile Mountain
View quadrangle was released in
preliminary form in December by the
California Department of Conservation.
It is now official after public review
and comment. The map is on file with
local government offices, including the
planning department, building department
and county recorder's office.
The "zone of required
investigation" for liquefaction covers
most of the flat ground that lies east
of the Foothill Expressway and north
from Highway 280 to the bay, including
the Naval Air Station at Moffett Field.
There are narrow
bands of liquefaction zones along Adobe,
Hale, Permanente and Stevens creeks.
Landslide Hazard Zones occur along the
steep stream banks in the Los Altos
Hills area. For more information,
contact your local building department.
Shaking causes most
of the damage during earthquakes, and in
many cases, it is cost effective to
retrofit houses and buildings to
minimize damage caused by severe
shaking. Local public libraries have a
number of publications by the Governors
Office of Emergency Services, American
Red Cross and the Federal Emergency
Management Agency that can be used as
guides to making homes more
Seismic Hazard Zone
maps produced by DOC's California
Geological Survey show areas at risk
from the secondary earthquake hazards of
landslides and liquefaction, which also
can be dangerous. It is generally not as
cost effective to retrofit an existing
building for the impacts of liquefaction
or landslides as it is to build in
safety features at the design stage.
Therefore, design changes are required
before new developments are approved and
constructed in order to be effective.
Changes made during the planning phase
can lessen the impact and better protect
life and property during future
earthquakes. The new maps are an
important tool that land developers will
use to ensure project feasibility.
Nine maps affecting
Northern California are now official.
The effort to identify and map seismic
hazards is ongoing. Preliminary Seismic
Hazard Zone maps for the east Bay Area
are scheduled for release in August. The
Cupertino and Los Gatos quadrangles are
currently being reviewed and will become
official in September.
Color copies of
official maps can be purchased through
DOC's California Geological Survey (415)
904-7707 or (916) 445-5716. The maps
also can be found on the Web
In addition to
studying and mapping earthquakes and
other geologic phenomena, the Department
of Conservation maps and classifies
areas containing mineral deposits;
ensures reclamation of land used for
mining; regulates oil, gas and
geothermal wells; administers
agricultural and open-space land
conservation programs; and promotes
beverage container recycling.