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SACRAMENTO – An
eight-year project to protect public
safety by zoning seismic hazards in Los
Angeles, Ventura and Orange Counties
took a major step toward completion
today as the California Department of
Conservation released five official and
nine preliminary maps.
Compiled by DOC’s
California Geological Survey, the maps
impact local planners, developers,
property sellers and real estate agents.
If property is
located in a Zone of Required
Investigation, where liquefaction or
earthquake-induced 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
buyers if property they're selling is in
a Seismic Hazard Zone, as is the case
when property is in a designated flood
zone.
Orange County became
the first county to be completely mapped
for those seismic hazards in December.
Four maps in
northeastern Los Angeles County – the
Condor Peak, Agua Dulce, Hi Vista and
Lovejoy Buttes quadrangles -- and the
Matilija quadrangle in Ventura County
became official today. The quadrangles
are about 60 square miles in size.
Fifteen other maps
for northeastern Los Angeles County are
in various stages of public review. The
newest – the final eight for the county
-- will become official in October. In
Ventura County, the last two preliminary
maps – covering the Ventura and Santa
Paula Peak quadrangles – will become
official in June and October,
respectively.
While the mapping
work in Los Angeles, Orange and Ventura
counties will soon be complete, zoning
continues in Northern California. The
California Geological Survey plans to
map parts of the Inland Empire, San
Diego and other Southern California
areas in the future.
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 Governor’s
Office of Emergency Services, American
Red Cross and the Federal Emergency
Management Agency that can be used as
guides to making homes more
earthquake-ready.
Seismic Hazard Zone
maps show areas at risk from the
secondary earthquake hazards of
landslides and liquefaction. 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
to better protect life and property
during future earthquakes are required
before new developments are approved and
built.
“The structures that
have been built in zoned areas since the
program began will be safer in the next
major earthquake than they would
otherwise have been,” Department of
Conservation Director Darryl Young said.
“With the knowledge of where
liquefaction and landslides are most
likely to occur, local officials can
require special engineering steps on new
construction that enhance public
safety."
Color copies of
official maps can be purchased through
DOC's California Geological Survey at
(213) 239-0878, (916) 445-5716, or (415)
904-7707. The maps also can be viewed
and downloaded
on the Web here.
Following is a brief
description of the seismic hazards shown
in each map:
LOVEJOY BUTTES:
This quadrangle consists of
unincorporated Los Angeles County land.
The center of the quadrangle is about 18
miles east of Palmdale and 45 miles
northeast of the Los Angeles Civic
Center. The liquefaction zone covers a
broad region in the western half of the
quadrangle in the vicinity of Big Rock
Wash and extends into the central part
of the quadrangle. There is a very small
landslide zone.
HI VISTA: Part
or all of the rural communities of Lake
Los Angeles, Wilsona Gardens and Hi
Vista are within the quadrangle, which
is 18 miles east of Lancaster and 50
miles northeast of the Los Angeles Civic
Center. There is a small landslide zone
and no liquefaction zones in the
quadrangle.
CONDOR PEAK: Small portions of
the cities of Los Angeles, Glendale and
Pasadena are in the southwestern quarter
of this map. The quadrangle is 15-20
miles north of the Los Angeles Civic
Center. Most of it is in the Angeles
National Forest, which cannot be
developed and thus was not evaluated.
The liquefaction zone covers the bottoms
of Big Tujunga Canyon and Mill Creek
Canyon near Hidden Springs. Landslides
and large rockslides are widespread and
abundant. The earthquake-induced
landslide zone covers about 74 percent
of the area evaluated in the quadrangle.
AGUA DULCE:
The quadrangle is centered 13 miles east
of Santa Clarita and 25 miles north of
Los Angeles. The unincorporated rural
communities of Agua Dulce and Soledad
are in the northern half; the Angeles
National Forest is in the southern half.
Zoning was limited to developable areas.
At present, development is limited to
rural homes and small ranches, aggregate
mining in Soledad Canyon, and
recreational facilities in Soledad
Canyon. Liquefaction zones exist in the
bottom of canyons, especially along the
Santa Clara River and Agua Dulce Canyon.
Although actual landslides are scarce,
steep slopes are common, and the
earthquake-induced landslide zone covers
about a third of the evaluated portion
of the quadrangle.
MATILIJA: This
quadrangle includes mostly mountainous
terrain in southern Ventura County. Most
of the City of Ojai, the only
incorporated land within the quadrangle,
lies along the eastern boundary. Several
unincorporated communities – Meiners
Oaks, Mira Monte, Live Oak Acres and Oak
View – are shown. Much of the land in
the quadrangle is being converted from
orchards to residential development.
About one-third of the quadrangle was
not evaluated for zoning because it lies
within the Los Padres National Forest.
Liquefaction zones cover the areas
around the Ventura River, San Antonio
Creek, Santa Ana and Poplin creeks north
of Lake Casitas, and a small portion of
the Ojai Valley. The earthquake-induced
landslide zone covers more than a third
of the evaluated portion of the
quadrangle.
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