This region of Russia is well known as a source of powerful earthquakes and equally powerful tsunamis. In the case of the 1923 earthquake the tsunami began as a twenty-five-foot wave and within half a day it reached Hawaii and California, causing damage and disruption there.
On February 3, 1923, an earthquake of magnitude 8.3 struck the east coast of Kamchatka, Russia, generating a twenty-five-foot tsunami that raced across the Pacific to Japan, Hawaii, and California. Local government documents show that this tsunami, at its origin, flooded low-lying coastal areas that were covered by thick snow. The unusual process of tsunami run-up without loss from ground friction is a result of the smoothing of the ground by ice. It was concluded that the tsunami flooded snowfields and deposited an extensive sheet of sand. A mixture of snow and seawater flooded over the area and caused damage to vegetation. Kamchatka is notorious for triggering earthquake tsunamis, and historical documents show that they have repeatedly caused considerable damage over the past two centuries. The tsunami from the 1923 earthquake caused an eight-inch rise in sea level at San Diego and a four-inch rise at San Francisco.
The Pacific Plate’s behavior is the key to the Kamchatkan earthquakes and tsunamis and its history is clearly illustrated in the evolution of the Hawaiian-Emperor Chain, a series of volcanic mountains stretching 4,000 miles across the North Pacific from Hawaii to a subduction zone at Kamchatka. The chain also provides a concrete illustration of sea floor spreading. The Pacific Plate, over millions of years, moved northwards and then northwestwards, first at a rate of three inches per year, then four inches, over the last seventy million years. Volcanic mountains in the chain older than seventy million years were carried down into the Kamchatka subduction zone and, as a subduction zone, every earthquake of the size of the 1823 quake carried the likelihood of a major tsunami.
The Kamchatka Peninsula is one of the most tectonically active regions of the world, and has historically experienced a number of large tsunamis. Assessing tsunami records is important for long-term tsunami prediction and for mapping the likely hazards. In the case of Kamchatka, historical records of tsunamis are too short to develop a predictive chronology of events. The way to obtain long-term data is to study paleo tsunamis, that is, to identify, map and date prehistoric tsunami deposits. These deposits also provide a proxy record of large earthquakes.
Paleo tsunami research became an active field of investigation in the late 1980s. Evidence of strong modern and pre-historic earthquakes and tsunamis has been found and studied in Japan, North America, and a number of other localities. At Kamchatka, studies of tsunami deposits began about 1990. Preliminary results suggest that the period from 0 to 1000 AD was particularly active. The combined record of tsunami deposits and of numerous marker tephra on Kamchatka offers an unprecedented opportunity to study tsunami frequency. It is possible to examine both the average frequency of events as well as the changes in frequency through time.
Some examples since 1923 of major earthquakes at the Kamchatka- Kuril-Islands (KKI) site provide good illustrations of the power of the tsunamis that follow. These outcomes are giving rise to increased efforts by national governments around the Pacific to anticipate and deal with tsunamis. In November of 1952, an unusually big quake occurred at KKI. It had a magnitude of 9 and it triggered Pacific-wide tsunamis in all directions toward the south and east. New Zealand experienced waves three feet high, Peru and Chile had lower wave heights, and Alaska and California had wave heights of four to five feet.
The area that suffered most from this tsunami was Hawaii. Altogether there was one million dollars’ worth of damage. In Oahu, boats and piers were destroyed and at the Big Island a bridge linking an outlying island to Hilo was shattered. The year 1958 saw another major earthquake from KKI, this time one of magnitude 8.3. Five years later there was an earthquake of 8.5 magnitude and, in 2002, another of magnitude 7.5. In November of 2006 there was one of magnitude 8.3 and, this time, the preparations that are described in the following paragraph were in place. The Pacific-wide tsunami alert was received in good time. This time Crescent City of California received the strongest hit. Two docks were damaged and several boats were tossed on to dry land. Waves were three feet above normal and they persisted for twenty minutes.
The U.S. National Tsunami Hazard Mitigation Program has representatives from the National Oceanic and Atmospheric Administration, the Federal Emergency Management Agency, the U.S. Geological Survey, and the states of Alaska, California, Hawaii, Oregon, and Washington. The program addresses three major tasks: hazard assessment, warning guidance, and mitigation. The first two tasks, hazard assessment and warning guidance, are led by physical scientists who, using research and modeling methods, develop products that allow communities to identify their tsunami hazard areas and receive more accurate and timely warning information.
The third task, mitigation, is handled by emergency organizations that use their experience and networks to translate science and technology into user-friendly planning and education projects. Their activities focus on assisting federal, state, and local officials as they plan for and respond to disasters. They also provide information for the public that is deeply affected by the impacts of both the disaster and the pre-event planning arrangements that have to be made.
