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The 1964 Alaskan earthquake, also known as the Great Alaskan earthquake and Good Friday earthquake, occurred at 5:36 P.M. AST on Good Friday, March 27.〔(US Geological Survey report on the earthquake )〕 Across south-central Alaska, ground fissures, collapsing structures, and tsunamis resulting from the earthquake caused about 139 deaths.〔 Lasting four minutes and thirty-eight seconds, the magnitude 9.2 megathrust earthquake was the most powerful recorded in North American history, and the second most powerful recorded in world history. Soil liquefaction, fissures, landslides, and other ground failures caused major structural damage in several communities and much damage to property. Anchorage sustained great destruction or damage to many inadequately earthquake engineered houses, buildings, and infrastructure (paved streets, sidewalks, water and sewer mains, electrical systems, and other man-made equipment), particularly in the several landslide zones along Knik Arm. Two hundred miles southwest, some areas near Kodiak were permanently raised by . Southeast of Anchorage, areas around the head of Turnagain Arm near Girdwood and Portage dropped as much as , requiring reconstruction and fill to raise the Seward Highway above the new high tide mark. In Prince William Sound, Port Valdez suffered a massive underwater landslide, resulting in the deaths of 30 people between the collapse of the Valdez city harbor and docks, and inside the ship that was docked there at the time. Nearby, a tsunami destroyed the village of Chenega, killing 23 of the 68 people who lived there; survivors out-ran the wave, climbing to high ground. Post-quake tsunamis severely affected Whittier, Seward, Kodiak, and other Alaskan communities, as well as people and property in British Columbia, Washington, Oregon, and California. Tsunamis also caused damage in Hawaii and Japan. Evidence of motion directly related to the earthquake was reported from all over the earth. ==Geology== At 5:36 p.m. Alaska Standard Time (3:36 a.m. March 28, 1964 UTC), a fault between the Pacific and North American plates ruptured near College Fjord in Prince William Sound. The epicenter of the earthquake was 12.4 mi (20 km) north of Prince William Sound, 78 miles (125 km) east of Anchorage and 40 miles (64 km) west of Valdez. The focus occurred at a depth of approximately 15.5 mi (25 km). Ocean floor shifts created large tsunamis (up to 220 feet (67 m) in height), which resulted in many of the deaths and much of the property damage.〔(Historic Earthquakes: Prince William Sound, Alaska )〕 Large rockslides were also caused, resulting in great property damage. Vertical displacement of up to 38 feet (11.5 m) occurred, affecting an area of 100,000 miles² (250,000 km²) within Alaska. Studies of ground motion have led to a peak ground acceleration estimate of 0.14 - 0.18 ''g''.〔National Research Council (U.S.). Committee on the Alaska Earthquake, (''The great Alaska earthquake of 1964, Volume 1, Part 1'' ), National Academies, 1968 p. 285〕 The Alaska Earthquake was a subduction zone earthquake (megathrust earthquake), caused by an oceanic plate sinking under a continental plate. The fault responsible was the Aleutian Megathrust, a reverse fault caused by a compressional force. This caused much of the uneven ground which is the result of ground shifted to the opposite elevation. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「1964 Alaska earthquake」の詳細全文を読む スポンサード リンク
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