![]() The station was inundated by at least 10 seismic sea waves which reached a maximum height of 25 feet above post-earthquake mean lower low water between 11:16 and 11:34 p.m. The Kodiak Naval Station, 5 miles southwest of Kodiak, was also severely damaged by the earthquake. The ground motion, however, did cause a massive short circuit and power failure at Kodiak. Inasmuch as most of Kodiak is underlain by bedrock or by only a thin veneer of unconsolidated sediments, very little if any damage occurred from ground motion or seismic shaking. Seismic shaking lasted 4½–5½ minutes at Kodiak and had a rolling motion. The subsidence also accelerated erosion of the unconsolidated sediments along the shoreline in the city of Kodiak. This bedrock presented a major post-earthquake construction problem because no sediments remained into which piles could be driven for foundations of waterfront facilities.īecause of tectonic subsidence, high tides now flood Mission and Potatopatch Lakes which, before the earthquake, had not been subject to tidal action. The waves scoured out 10 feet of sediments in the channel between Kodiak Island and Near Island and exposed bedrock. The violently destructive seismic sea waves not only severely damaged homes, shops, and naval-station structures but also temporarily crippled the fishing industry in Kodiak by destroying the processing plants and most of the fishing vessels. They moved from the southwest and northeast: and reached their maximum height of 20–30 feet above mean lower low water at Shahafka Cove between 11:00 and 11:45 p.m., March 27. The waves struck the town during the evening hours of March 27 and early morning hours of March 28. The seismic sea waves destroyed all but one of the docking facilities and more than 215 structures many other structures were severely damaged. Damage was caused chiefly by 5.6 feet of tectonic subsidence and a train of 10 seismic sea waves that inundated the low-lying areas of the town. The largest community, Kodiak, had the greatest loss from the earthquake. Property damage and loss of income to the communities is estimated at more than $45 million. It was the most severe earthquake to strike this part of Alaska in modern time, and took the lives of 18 persons in the area by drowning this includes two in Kodiak and three at Kaguyak. In 1912, a series of M7+ earthquakes was associated with the Novarupta eruption, which was the world’s largest volcanic eruption of the 20th century.The great earthquake (Richter magnitude of 8.4–8.5) that struck south-central Alaska at 5:36 p.m., Alaska standard time, on Ma(03:36, March 28, Greenwich mean time), was felt in every community on Kodiak Island and the nearby islands. (3) Crustal seismicity in this region can be attributed to the Kodiak Shelf fault zone and the volcanic arc. ![]() Both earthquakes caused damage and disruption in the town of Kodiak and other communities on the island. The most notable examples of such earthquakes are the M7.0 events in 1999 and M6.9 on Kodiak Island in 2001. The Aleutian-Alaska-Wadati-Benioff Zone produces thousands of earthquakes each year, most of which are too deep and small to be felt. In the Alaska Peninsula region, seismicity decreases at a depth of about 150 miles (241 km), reflecting the downdip extension of the Pacific Plate. This zone extends along the Aleutian Arc, the Alaska Peninsula and Cook Inlet. (2) Intermediate depth seismicity (below 20 miles/32 km) occurs in the Wadati-Benioff Zone, where the subducting Pacific Plate is sinking toward the mantle beneath the North American Plate. ![]() While these recent earthquakes did not produce damaging tsunamis, previous tsunamis have been documented in historical records of Russian communities and in recently discovered paleo-tsunami deposits. Recent examples include the M7.8 Simeonof earthquake in 2020 beneath the Shumagin Islands and the M8.2 Chignik earthquake in 2021 southwest of Kodiak Island. Seismicity in the Alaska Peninsula region is caused by several tectonic features: (1) The Aleutian Megathrust is the source of the strongest earthquakes in the region. Tectonic position of the Alaska Peninsula
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