Anatolian tectonic plate, north anatolian fault, historical earthquakes Greece, Attica, Earthquakes, Tsunami, , Hurricanes, Volcanic Eruptions and other Natural and Man-Made Hazards and Disasters - by Dr. George Pararas Carayannis

 

Tsunami, Earthquakes, Hurricanes, Volcanic Eruptions and other Natural and Man-Made Hazards and Disasters

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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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