The 1964 Alaska Earthquake

1. The 1964 Alaska Earthquake & The Tsunami It Created Click Here To Read Some Interesting Earthquake Facts Mrs. Degl

2. Mrs. Degl

3. The map below shows earthquakes around the globe. They are not evenly distributed; the boundaries between the plates grind against each other, producing most earthquakes. Most of the world’s earthquakes occur on plate boundaries. Mrs. Degl

4. There are three main tectonic boundaries: divergent (extensional), convergent (compressional) and transform. Plate boundaries in different localities are subject to different inter-plate stresses. Each type has its own special hazards. The San Andreas Fault in California is a transform plate boundary. This means that the plates are sliding past each other. There are not any plates moving up or down. The plate boundary that runs under Alaska is a convergent/compressional fault. Mrs. Degl

5. On March 27, 1964, at 5:36 p.m. a great earthquake of magnitude 9.2 occurred in Prince William Sound region of Alaska. The epicenter was about 10 km east of the mouth of College Fiord, approximately 90 km west of Valdez and 120 km east of Anchorage. The epicenter was located at Lat. 61.04N, Lon. 147.73W, at a depth of approximately 25 km. This earthquake is the second largest earthquake ever recorded in the world, after a magnitude 9.5 earthquake in Chile in 1960. The duration of rupture lasted approximately 4 minutes. The northwestward motion of the Pacific plate at about 5 to 7 cm per year causes the crust of southern Alaska to be compressed and warped, with some areas along the coast being depressed and other areas inland being uplifted. After periods of tens to hundreds of years, this compression is relieved by the sudden southeastward motion of portions of coastal Alaska as they move back over the subducting Pacific plate. As a result of the 1964 quake, the Latouche Island area moved about 18 meters to the southeast.     In the first day there were 11 aftershocks with magnitudes greater than 6.0; in the next three weeks there were 9 more. Smaller aftershocks continued for more than a year. Mrs. Degl

6. The damage totaled 300-400 million dollars (1964 dollars). The number of deaths from the earthquake totaled 131; 115 in Alaska and 16 in Oregon and California. The death toll was extremely small for a quake of this magnitude due to low population density, the time of day and the fact that it was a holiday (it was Good Friday), and the type of material used to construct many buildings (wood). This six story building collapsed as a result of the earthquake. Mrs. Degl

7. Mrs. Degl

8. Group Discussion • In your group, select one designated speaker to describe to the class your thoughts on the following questions. • Describe the different types of damage that an earthquake can cause. • Describe what you can do in your own home to eliminate or reduce earthquake hazards to your family. • What would you include in an emergency earthquake kit to keep in your home if you lived in Alaska or another earthquake prone area? • What should you do during an earthquake? Mrs. Degl

9. The Tsunami The Great 1964 Alaska earthquake generated catastrophic tsunami waves that devastated many towns in the Prince William Sound area of Alaska, along the Gulf of Alaska, along the West Coast of Canada and the United States, and in the Hawaiian islands. In Alaska, the tsunami height measurements varied from 6.1 m at Kodiak Island, 9.1 m at Valdez, 24.2 m at Blackstone Bay, and 27.4 m at Chenega. A total of 119 people lost their lives in Alaska, Oregon and California as a result of tsunami waves generated in the Gulf of Alaska and the locally generated tsunami waves in Prince William Sound. Most of the damage and most of the lives lost in Alaska were due to large local tsunami waves within the Prince William Sound area, rather than to the earthquake itself. Of the 119 deaths attributable to tsunami waves, about one-third were due to the open-ocean tsunami generated in the Gulf of Alaska. Although most studies refer to the March 27, 1964 Great Earthquake in Alaska as having generated one single tsunami, in reality there were two different types of very distinguishable tsunami generation mechanisms associated with this earthquake: one along the continental shelf bordering the Gulf of Alaska; the other, in the Prince William Sound region. Mrs. Degl

10. Tsunamis are ocean waves produced by earthquakes. The word comes from Japanese and means "harbor wave," because of the devastating effects these waves have had on low-lying Japanese coastal communities. Tsunamis are often incorrectly referred to as "tidal waves." Not all earthquakes produce tsunamis, but when they do, the waves may sweep ashore causing damage locally and at places thousands of miles from the earthquake epicenter. Mrs. Degl

11. Thinking Ahead Assignment • The class will split into groups of 2 or 3. Each group, while sitting together in the computer lab, will visit the following websites, and any others you may find useful to complete both parts of the assignment. • http://seagrant.uaf.edu/features/earthquake/hazards.html • http://mceer.buffalo.edu/infoService/faqs/eqlist.asp • http://nysun.com/article/6883 • The assignment is to summarize the other geological hazards that pose a threat to Alaskan people and property. You must describe the hazard, the specific damage it may cause, and make suggestions as to how the Alaskan people can take actions to minimize damage ahead of time. • B) Now you do the same as you did above, but this time the location is New York City. Mrs. Degl