The 1964 Alaska earthquake, also known as the Great Alaska earthquake, began at 5:36 P.M. AST on Friday, March 27, 1964. Across south-central Alaska, ground fissures, collapsing buildings, and tidal waves directly caused about 131 deaths. This Alaskan earthquake is also known as the Good Friday quake because it occurred during a Christian holy day associated with the crucifixion of Jesus and an earthquake that reportedly happened then.
Lasting nearly five minutes, it was the most powerful recorded earthquake in U.S. and North American history, and the third most powerful ever measured by seismograph; it had a moment magnitude of 9.2 and registered 8.4 on the Richter scale.
The powerful earthquake produced Earthquake liquefaction in the region. Ground fissures and failures caused major structural damage in several communities, much damage to property and several landslides. Anchorage sustained great destruction or damage to many houses, buildings, and infrastructure (paved streets, sidewalks, water and sewer mains, electrical systems, and other man-made equipment). Two hundred miles southwest, some areas near Kodiak were permanently raised by . East of Anchorage, areas around the head of Turnagain Arm near Portage dropped , requiring reconstruction and fill to raise the Seward Highway above the new high tidemark. In Prince William Sound, a tsunami destroyed the village of Chenega, killing 23 of the 68 people who then lived there; survivors out-ran the wave, climbing to high ground. Post-quake tsunamis severely affected Valdez, Whittier, Seward, Kodiak, and other Alaskan Communities, as well as people and property in British Columbia, Oregon, and California. Tsunamis caused damage in Hawaii and Japan.
At 5:36 p.m. Alaska Standard Time (3:36 a.m. March 27, 1964 UTC), just as people were traveling home on a late-winter evening, 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 rupture occurred at a depth of approximately 15.5 mi (25km). Ocean floor shifts created large tsunamis (up to 70 feet (20 m) in height), which resulted in many of the deaths and much of the property damage. Large rockslides were also created which resulted 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.
The hamlets of Girdwood and Portage, located 30 and 40 mi (60 km) southeast of Anchorage on Turnagain Arm, were destroyed by subsidence and subsequent tidal action. About of the Seward Highway sank below the high-water mark of Turnagain Arm; the highway and its bridges were raised and rebuilt in 1964-65.
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