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Historical Tsunamis
In California - The Tsunami Threat in California
George Pararas-Carayannis
(Excerpts
from a book under preparation)
Historical Tsunamis
from Distant Sources
In this century, there
have been numerous tsunamis generated from distant earthquakes
that have reached California. Most recently, tsunamis were observed
in 1946, in 1952, in 1957, in 1960, and in 1964. The 1964 tsunami
was the most damaging.
 The
Effects of the 1964 Alaska Tsunami : (Described in detail elsewhere
in these pages) The
Great Alaskan Earthquake of March 28, 1964 generated a great
tsunami which was extremely damaging, not only in Alaska, but
along Vancouver Island, and in Northern California. Hardest hit
was Crescent City, California, where eleven persons lost their
lives.
The tsunami waves
affected the entire California coastline, but were particularly
high from Crescent City to Monterey with heights on the open
coast ranging from 7 - 21 feet. At Santa Cruz Harbor, the tsunami
wave reached as high as 11 feet, sinking a hydraulic dredge and
a 38 foot cabin cruiser and causing minor damage to the floating
docks.
Damage in San Francisco
Bay was largely to pleasure boats. The highest damage was reported
from marinas in Marin County where strong currents induced by
the tsunami caused boats and floating piers to break loose and
strike other craft.
Damage at Noyo Harbor
was primarily to floating piers and to commercial fishing vessels.
Also, damage occurred in the City of Los Angeles and Long Beach Harbors.
The estimated losses elsewhere along California were between
$1,500,000 and $2,375,000 (1964 dollars), while at Crescent City
tsunami damage was estimated at $7,414,000.
The maximum wave at
Crescent City was approximately 20 to 21 feet. Crescent City
Harbor is one of the oldest. Lumbering and timber products are
the major industries. The first of the four tsunami waves that
struck Crescent City caused no significant damage other than
flooding. The second and third waves were smaller than the first.
The fourth was the largest of the waves and was preceded by a
withdrawal of the water which left the inner harbor almost dry.
The fast moving fourth wave capsized 15 fishing boats in the
harbor. Three other boats disappeared, and eight more sunk in
the mooring area. Several other boats were washed onto the beach.
Extensive damage was inflicted to the piers. The tsunami waves
covered the entire length of Front Street, and about thirty blocks
of Crescent City were devastated. Lumber, automobiles, and other
objects carried by the waves were responsible for a good portion
of the damage to the buildings in the area. Fires started when
the largest tsunami wave picked up a gasoline tank truck and
slammed it against electrical wires. The fire spread quickly
to the Texaco tank farm, which burned for three days.
The Tsunami
Threat in California
Threat from Distant
Sources: Large earthquakes
of distant or local origin can cause tsunamis which can be very
damaging in California. Of these, tsunamis generated from distant
earthquakes pose the greatest threat for California, particularly
those generated in the Aleutian Islands and Alaska. The frequency
of occurrence for such events is considered relatively high.
Northern California is particulary susceptible to such distantly
- generated tsunamis, while Southern California is affected to
a much lesser extent.
The Crescent City
area in Northern California is well known for its tsunami vulnerability.
In other areas, such as Halfmoon Bay, Santa Monica Bay, and the
northern portion of Monterey Bay, tsunami waves from distant
sources can set up resonant oscillations which will amplify the
height of tsunamis and can result in damage. For example, the
1946 tsunami from the Aleutian Islands produced no noticeable
wave at the city of Monterey, on the southern side of Monterey
Bay, but the tsunami waves reached over 10 feet (3.5 m) at Santa
Cruz, on the northern side of the bay.
Threat from Local
Earthquakes: The
relative tsunami threat for local tsunamis in California can
be considered as being relatively low because of the low recurrence
frequencies from these disasters. The recurrence frequency of
large tsunamis in California has been estimated to be once every
100 years. Between 1812 and 1988, thirteen possible tsunamis
have been observed or recorded from local earthquakes. These
events were poorly documented and some are questionable. There
is no doubt that earthquakes occurring on submarine faults, off
Santa Barbara, could generate large destructive local tsunamis.
Perhaps the size of the 1812 tsunami was exaggerated in the historical
records, but one and possibly two large tsunamis did occur in
the area and can occur again in the future (detailed account of the 1812 events at Santa
Barbara will be provide elsewhere in these pages) . Also, the 1927 earthquake
off Point Arguello with magnitude 7.3 produced small local tsunamis
at Surf (1.8 m) and at Port San Luis (1.4 m). The other faults
of the San Andreas, although capable of strong earthquakes, cannot
generate any significant tsunamis. Only earthquakes in the Transverse
Ranges, specifically the seaward extensions in the Santa Barbara
Channel and offshore area from Point Arguello, can generate local
tsunamis of any significance. The reason for this may be that
earthquakes occurring in these regions result in a significant
vertical displacement of the crust along these faults. Such tectonic
displacements are necessary for tsunami generation. The area
offshore of Point Arguello has sea-floor features which suggest
such displacements, so, future local tsunamis from this area
can be expected.
REFERENCES
IIDA, K., D.C. Cox,
and Pararas--Carayannis, George, 1967.
Preliminary Catalog
of Tsunamis Occurring in the Pacific Ocean. Data Report No. 5. Honolulu: Hawaii Inst.Geophys.Aug.
1967.
PARARAS-CARAYANNIS
George, THE BIG ONE (Book in Preparation)
TUDOR, W.J., 1964.
Tsunami Damage at
Kodiak, Alaska, and Crescent City, California from Alaskan Earthquake
of 27 March 1964,
U.S. Navy Civil Engr. Lab, Port Hueneme, Calif., Tech. Note N-622,
124 pp.
SEE
ALSO
The
March 27, 1964, Great Alaska Earthquake
Source
Mechanism of the March 27, 1964, Great Alaska Earthquake and
Tsunami
The
March 27, 1964 Tsunami in the Gulf of Alaska
The
March 27, 1964 Tsunami Waves in Prince William Sound, Alaska
The
Effects of the March 27, 1964 Alaska Tsunami in Canada
The
Effects of the March 27, 1964 Alaska Tsunami In California
The
Santa Barbara, California, Earthquakes and Tsunami(s) of December
1812
The
Effects of the March 27, 1964 Alaska Tsunami in the Hawaiian
Islands
A
Brief History of California
The
Next Great California Earthquake
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