Alaska Earthquake

On March 27, 1964 the most powerful earthquake recorded in North America struck in the heart of Prince William Sound at 5:36pm. Buildings fell and entire towns were washed away by the tsunami that followed in the aftermath of the powerful earthquake. However, considering the sheer magnitude of the earthquake, Alaska suffered minimal damage to its residents and economy for a number of reasons. On the contrary, the Alaskan economy temporarily prospered from the '64 earthquake by receiving additional federal support and funding in a time when military presence was declining, unemployment was growing, and before the drilling of oil in Prudhoe Bay.

"I recall during one tremor, the ground under the driveway opened up and we watched the big Plymouth slide slowly backward into the crevasse. Then the ground shifted again, noisily crushing the car as the crevasse closed." Julie Persons account of the Ð''Great Earthquake of '64' is one of many devastating reminders of the tragedy that occurred on the Good Friday over forty years ago. However, casualties were significantly low for such a powerful disaster, both physically and economically. The purpose of this paper is to provide a general overview of the 1964 Alaskan earthquake and describe the economic effects that followed.

The extensive geological disruption and strength has caused the '64 earthquake to become one of the most studied earthquakes in history. However, the continual research being conducted has lead to a wide array of contradictory information. Because no seismic instruments capable of recording strong ground motions were in Alaska before the earthquake, most measurements were calculated from tele-seismic records. According to a book sanctioned by the Committee on the Alaska Earthquake of the Division of Earth Sciences National Research Council in 1970, the magnitude of the '64 earthquake on the Richter scale ranged between 8.3 and 8.6. Although these two numbers do not appear to range significantly, the amount of energy released by an 8.6 strength earthquake is double of that released by an 8.3. Newer research has estimated the strength of the Alaskan earthquake at a 9.2 on the Moment Magnitude scale, making it the third strongest earthquake in the world and strongest in the Northern Hemisphere.

More recent research in the late 1980's and 1990's has shed light on the cause of the '64 earthquake. Dr. George Pararas-Carayannis, one of the nation's foremost authorities on earthquakes and tsunamis, states "The Pacific tectonic plate movement caused the crust of southern Alaska to be compressed and warped, with some areas along the coast being depressed while other areas inland are being uplifted. At time intervals ranging from tens to hundreds of years, this compression is relieved by the sudden motions of large portions of the coastal portion of Alaska moving back in a southeastern direction over the subducting Pacific plate." In short, the Pacific plate was being pushed under the North American plate.

The Epicenter, location on the earths surface directly above focus, of the '64 earthquake is located in the northern part of the Prince William Sound; specifically 61.04Ð'Ñ" N- 147.73Ð'Ñ" W, approximately 75 miles east of Anchorage. The focus, or depth of the earthquake, is estimated at 25 miles below the epicenter. In general, the lower the earthquake occurs below the surface of the earth, the weaker it is; 25 miles is relatively close to the surface compared to most earthquakes that occur in Alaska.

Another component of research modified as science improved is the total land area affect by the '64 earthquake. Early research by the National Committee on the Alaska Earthquake reported a total damage zone to be about 80,500 kilometersÐ'І and the total area felt by the earthquake to be about 850,000 kilometersÐ'І. Current research states the damage area was about 130,000 kilmetersÐ'І and the total area felt by the earthquake about 1,300,000 kilometersÐ'І. The Yukon Territory in Canada and the State of Washington both felt the effects of the '64 earthquake.

One of the most notable aspects of the '64 earthquake is the duration. The lack of seismic instruments in Alaska at the time has resulted in the length of the earthquake to be estimated from a variety of personal accounts. Although most early accounts of the earthquake range from 2 to 6 minutes, recent research has concurred that the earthquake lasted about 4 minutes (240 sec.) from beginning to end. One survivor who was wintering at the Ward Cannery in Kenai estimated the duration of the earthquake at half an hour; however, this may be due to the several immense aftershocks that followed.

Of the 52 large aftershocks, the first 11 rated 6.0 or higher on the Richter scale during the first 24 hours after the main earthquake. During the next three weeks, nine earthquakes of the same magnitude followed. Thousands of smaller earthquakes pursued for a year in the same 250 kilometer area where the main earthquake took place.

No other earthquake recorded has had more geologic disruption than Alaska in 1964. Vertical displacements, either uplift of subsidence, affected an area over 520,000 kilometersÐ'І. Areas near the epicenter of the earthquake uplifted permanently as much as 15 meters. Montague Island suffered an uplift of 11.5 meters. Subsidence occurred over an area of 285,000 kilometersÐ'І, causing areas of Kodiak, most of the Kenai Peninsula, and the north and west parts of Prince William Sound to subside as much as 9 meters. A Geological Survey by Hanson and others in 1966 reported that the Native villages of Chenga, Kaguyak, Old Harbor, and Afognak were all forced to relocate because the areas in which the villages were located subside significantly.

The '64 earthquake caused extensive structural and geological damage; however, 90% of the 131 lives lost were caused by the tsunamis that followed. Within minutes of the earthquake, 5 tsunamis were created by seafloor disruption. The first tsunami arrived in Seward about 20 minutes after the earthquake ended, causing the annihilation of 13 structures. The largest wave height recorded occurred at Soup Bay in the Valdez Inlet measuring about 67meters (219ft). The tsunamis along with a submarine slide off the delta on which Valdez was built caused all port facilities as well as most of the other structures in the vicinity of the water to be destroyed. Thirty-two deaths occurred in Valdez as a result of the tsunami.

Areas within the Prince William Sound area along with Kodiak suffered the most severe damage from the tsunami, resulting in over $84 million dollars worth of damage. However, tsunami waves caused by the '64 earthquake

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