Aleutian Island earthquake
Encyclopedia
The 1946 Aleutian Islands earthquake was an earthquake
near the Aleutian Islands on April 1, 1946. It was followed by a Pacific-wide tsunami
. The earthquake was a magnitude 7.8, with its epicenter at 52.8°N, 163.5°W, and focal depth of 25 km. It resulted in 165 casualties (159 people on Hawaii
and six in Alaska
) and over $26 million in damages. Multiple destructive waves at heights ranging from 45 – 130 ft occurred.
It obliterated the Scotch Cap Light
house on Unimak Island
, Alaska. among others, and killed all five lighthouse keepers. The wave reached Kauai
4.5 hours after the quake, and Hilo 4.9 hours later. This prompted the creation of the Seismic Sea Wave Warning System, which later became the Pacific Tsunami Warning Center
in 1949.
The tsunami was unusually powerful for the size of the earthquake; it was the last time any earthquake below magnitude 9.0 caused tsunami fatalities far from the earthquake area. Due to the discrepancy between the size of the tsunami and the relatively low magnitude on the surface wave magnitude
scale, it is classified as a tsunami earthquake
.
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
near the Aleutian Islands on April 1, 1946. It was followed by a Pacific-wide tsunami
Tsunami
A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake...
. The earthquake was a magnitude 7.8, with its epicenter at 52.8°N, 163.5°W, and focal depth of 25 km. It resulted in 165 casualties (159 people on Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
and six in Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
) and over $26 million in damages. Multiple destructive waves at heights ranging from 45 – 130 ft occurred.
It obliterated the Scotch Cap Light
Scotch Cap Light
The Scotch Cap Light is a lighthouse located on the southwest corner of Unimak Island in Alaska. It was the first station established on the outside coast of Alaska.-History:...
house on Unimak Island
Unimak Island
Unimak Island is the largest island in the Aleutian Islands chain of the U.S. state of Alaska. It is the easternmost island in the Aleutians and, with an area of 1,571.41 mi² , the ninth largest island in the United States and the 134th largest island in the world. It is home to Mount...
, Alaska. among others, and killed all five lighthouse keepers. The wave reached Kauai
Kauai
Kauai or Kauai, known as Tauai in the ancient Kaua'i dialect, is geologically the oldest of the main Hawaiian Islands. With an area of , it is the fourth largest of the main islands in the Hawaiian archipelago, and the 21st largest island in the United States. Known also as the "Garden Isle",...
4.5 hours after the quake, and Hilo 4.9 hours later. This prompted the creation of the Seismic Sea Wave Warning System, which later became the Pacific Tsunami Warning Center
Pacific Tsunami Warning Center
The Pacific Tsunami Warning Center is one of two tsunami warning centers that are operated by NOAA in the United States. Headquartered in Ewa Beach, Hawaii, the PTWC is part of an international tsunami warning system program and serves as the operational center for TWS of the Pacific issuing...
in 1949.
The tsunami was unusually powerful for the size of the earthquake; it was the last time any earthquake below magnitude 9.0 caused tsunami fatalities far from the earthquake area. Due to the discrepancy between the size of the tsunami and the relatively low magnitude on the surface wave magnitude
Surface wave magnitude
The surface wave magnitude scale is one of the magnitude scales used in seismology to describe the size of an earthquake. It is based on measurements in Rayleigh surface waves that travel primarily along the uppermost layers of the earth...
scale, it is classified as a tsunami earthquake
Tsunami earthquake
A tsunami earthquake is an earthquake that triggers a tsunami of a magnitude that is very much larger than the magnitude of the earthquake as measured by shorter-period seismic waves. The term was introduced by Hiroo Kanamori in 1972. Such events are a result of relatively slow rupture velocities...
.