1946 Aleutian Tsunami

 

Cause of Event

During the early morning of April 1, 1946, an earthquake of magnitude 7.4 occurred in an area of the Aleutian Trench located approximately 90 miles south of Unimak Island, part of the Aleutian Island chain (see diagram above for approximate location of quake's epicenter). During the quake, a large section of seafloor was uplifted along the fault where the quake occurred, producing a large, Pacific-wide tectonic tsunami. The most detailed, and well documented accounts of the 1946 Aleutian tsunami come from Scotch Cap, located on Unimak Island, and the Hawaiian Islands. Despite its enormous size at Scotch Cap, the 1946 tsunami had little effect on the Alaskan mainland, due to the presence of the Aleutian Islands, which absorbed the brunt of the tsunami's power, shielding the mainland.

 Effects at Scotch Cap

Approximately 48 minutes after the earthquake, a 100-foot tsunami struck the area of Scotch Cap. The tsunami completely destroyed the newly built US Coast Guard lighthouse, surging over the costal cliff to a height of 42 m (135 ft.) above sea level. All five members of the lighthouse crew were killed. Please click on the map and photos below for more information.


Effects at Hawaii

  At approximately 7 a.m., less than five hours after the earthquake in Alaska, the first of several tsunami waves reached the Hawaiian Islands. The tsunami caught Hawaii completely unaware, as the destruction at Scotch Cap prevented the transmission of any warning message until it was too late. The tsunami waves produced extensive destruction along the shorelines of the Hawaiian Islands, especially at Hilo, on the big island of Hawaii, where the city's entire waterfront was destroyed. Wave heights across the Islands reached an estimated maximum of 55 feet, 36 feet and 33 feet on Hawaii, O'ahu, and Maui, respectively. The tsunami inundated areas up to a half a mile inland in some locations. A total of 159 people were killed as a result of the tsunami in Hawaii. Please click on the photos below for scenes from the disaster.  


 Effects at Other Pacific Locations

 

The effects of the tsunami were also felt along the west coast of the United States. The community of Taholah, Washington was struck by an approximate five-foot surge, which damaged several boats in the harbor. Coo's Bay, Oregon reported a ten-foot wave. In California, Fort Bragg reported five- to nine-foot waves, and a 13.5-foot wave hit Muir Beach. The Half Moon Bay area was struck by waves estimated at 10 to 14 feet high, which damaged several boats and structures along the waterfront, and caused an estimated 20,000 dollars in damage. One person drowned as a result of the ten-foot waves that struck Santa Cruz. The tsunami was also noticed in Santa Barbara and the greater Los Angeles area.

The 1946 Aleutian Tsunami crossed the Pacific, producing waves up to 30 feet high in some locations at the Marquesas Islands in French Polynesia, and even had the power to damage fishing boats in Chile.

 
 

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