Agenda - City of Santa Monica

THREAT ASSESSMENT 1 – MAJOR EARTHQUAKE
General Situation
Since 1800 there have been approximately 60 damaging seismic events, or
"earthquakes," in the Los Angeles region. After a brief hiatus between major events
(circa 1940-1972), the greater Los Angeles area has experienced a number of
moderate events which have resulted in considerable disruption of the infrastructure,
impact on social and economic life, loss of lives and extensive property damage within
the City of Los Angeles, the greater metropolitan area and the adjacent region including
Santa Monica. According to the Geological Survey's records, some 20 quakes of
magnitude 6.0 or higher have occurred in Southern California since 1912. The most
recent of these was the M6.7, 1994 Northridge Earthquake which was centered in the
northwest part of the City, in the general vicinity of the 1971 San Fernando (a.k.a.
Sylmar) quake.
Following the 1994 Northridge and 1995 Kobe, Japan earthquakes, a variety of studies
and cooperative information exchange ventures were initiated to expand knowledge
concerning earthquakes so that people could be better protected in the event of future
significant seismic events. Kobe, Northridge and other seismic event information are
being used in formulating methodologies for strengthening buildings and structures to
more successfully withstand severe damage and to better protect occupants and
equipment during various types and degrees of seismic events.
The California State Geologist's Seismic Hazards Mapping Program has provided maps
that identify amplified shaking, liquefaction and landslide hazard zones. These maps are
used in revising the City’s building, zoning and other codes, plans, standards,
procedures and/or development permit requirements.
Based on Richter scale and pre-Richter calculations, the second most-powerful tremor
recorded in Los Angeles proper was in 1923 and centered in the San Jacinto
Mountains, southeast of the City. The M6.3 earthquake caused only light damage in Los
Angeles. In 1918, also in the isolated San Jacinto Mountains, some 150 miles from
downtown, a mighty M6.8 quake occurred.
Los Angeles experienced two quakes of identical 6.3 magnitude - one in the Long
Beach area in 1933 and another in Santa Barbara in 1925—that produced disastrous
damage because their epicenters were near central cities. The Long Beach toll was $40
million in property destruction and 115 lives lost. The Santa Barbara shake leveled
much of the business district at a $6 million loss there, and killing 20.
An earthquake in 1927 ranks--along with Tehachapi-Bakersfield in 1952--as the all-time
southern California strongest earthquakes. Registering at M7.5, the 1927 upheaval
centered just north of Point Arguello in the upper Santa Barbara channel, destroying
railways bridges, crumbling cliffs and sending a seismic wave as far north as Pismo
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