|
SACRAMENTO -- The
California Department of Conservation
today released six maps for the
Lancaster-Palmdale area that help
protect public safety in the event of a
large earthquake.
“Once we know where
the potential problems are most likely
to occur, we can improve public safety
by requiring builders to take
preventative steps to minimize the
hazard,” Acting State Geologist Michael
Reichle said.
These Seismic Hazard
Zone Maps identify areas that are
subject to liquefaction and landslides.
Those hazards are potential side effects
of earthquakes in the magnitude 5.5 or
greater range. Landslides and
liquefaction can cause destruction over
and above the damage done by shaking.
Liquefaction occurs when
water-saturated, sandy soil is violently
shaken and temporarily loses its ability
to support structures. Liquefaction was
a major cause of damage in Kings Harbor
area of Redondo Beach during the
Northridge earthquake of 1994. The
Northridge earthquake also caused more
than 11,000 landslides, some of which
damaged structures or blocked roads.
The new maps, created
by DOC’s California Geological Survey,
establish Zones of Required
Investigation. If property is located in
a zone, the local building department
must require -- before permits are
issued -- that a registered geologist
investigate the site to determine
whether mitigation steps are necessary.
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.
“The structures that
have been built in zoned areas since the
program began will be safer in the next
big earthquake than they otherwise would
have been,” said Chuck Real, the
Supervising Geologist in charge of the
Seismic Hazard Zone Mapping Program.
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.
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. Thus, the Seismic Hazard Zone
maps are aimed primarily at new
construction. They require that design
changes - such as deep foundations in
liquefaction zones and slope
stabilization in landslide zones - be
made in the planning stage.
Each map covers about
a 60-square mile area known as a
“quadrangle.” Here's a closer look at
what each map shows:
♦ Rosamond
Quadrangle: This map shows land in both
Los Angeles and Kern counties in the
central Antelope Valley, centered about
10 miles north of Lancaster. The Kern
County portion was not evaluated.
Portions of Lancaster and Edwards Air
Force Base are covered in this map. No
earthquake-induced landslide zones were
identified. The liquefaction zone covers
an area along the eastern margin of the
quadrangle, where recent groundwater
depths have been less than 40 feet; an
area occupied by the wash of Amargosa
Creek; and the sewage treatment facility
at State Route 14 and Avenue D.
♦ Del Sur Quadrangle:
About 1.5 square miles of the
southeastern corner of this map are
within the Palmdale city limits.
Portions of Lancaster -- North of Avenue
M and/or the California Aqueduct and
east of 110th Street West – also are
included. Liquefaction zones are noted
in the Leona Valley and the narrow
trough-like valley to the north, the
bottoms of canyons, and within wash
areas. Earthquake-induced landslide
zones cover about 3 percent of the
quadrangle.
♦ Lancaster West
Quadrangle: Most of the land in the map
area is within the City of Lancaster,
including the community of Quartz Hill.
The land east of the Antelope Valley
Freeway south of Avenue M is within
Palmdale’s city limits, as is a small
area south of Avenue N in the
southwestern corner. The liquefaction
zone includes a swath of low ground to
the west of Lancaster; the Amargosa
Creek channel; and water-reclamation
ponds at the county park at the east end
of Fox Air Field. There are no zones for
potential landslides.
♦ Lancaster East
Quadrangle: Portions of Lancaster and
Palmdale are covered. The liquefaction
zone is limited to the narrow Little
Rock Wash. The terrain is nearly level,
and no landslide hazards are noted.
♦ Alpine Butte
Quadrangle: Part of the eastern boundary
of Palmdale and a few square miles of
Lancaster located between Avenue J and
Avenue K are on this map, although there
are only scattered rural homes and
ranches in the coverage area. There are
no liquefaction zones on this map. Very
small patches on Alpine Butte and Rocky
Buttes lie within the earthquake-induced
landslide zones that make up less than
one percent of the quadrangle.
♦ Little Buttes
Quadrangle: No seismic hazard zones were
identified. The Little Buttes Quad is in
central Antelope Valley along the
boundary of Los Angeles and Kern
counties. The Kern County portion was
not evaluated. The center of the
quadrangle is approximately 15 miles
northwest of Lancaster. Small parcels of
the City of Lancaster extend into the
southeastern corner, east of 70th Street
West and between 100th and 110th Street
West. The rural community of Antelope
Acres is also in the southeastern
quarter of the quadrangle.
# # #
|