The 1965 Rat Islands earthquake occurred at 05:01 UTC, on 4 February (19:01, 3 February local time). It had a magnitude of 8.7 and triggered a

tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater exp ...

of over 10 m on Shemya Island, but caused very little damage.

Tectonic setting

The

Rat Islands The Rat Islands ( ale, Qax̂um tanangis, russian: Крысьи острова) are a group of American volcanic islands in the Aleutian Islands in southwestern Alaska, between Buldir Island and the Near Islands group to its west, and Amchitk ...

form part of the

Aleutian Islands The Aleutian Islands (; ; ale, Unangam Tanangin,”Land of the Aleuts", possibly from Chukchi ''aliat'', "island"), also called the Aleut Islands or Aleutic Islands and known before 1867 as the Catherine Archipelago, are a chain of 14 large v ...

, a chain of volcanic islands forming an island arc, that results from the

subduction Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, ...

of the

Pacific Plate The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate. The plate first came into existence 190 million years ago, at the triple junction between the Farallon, Phoenix, and I ...

beneath the

North American Plate The North American Plate is a tectonic plate covering most of North America, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. With an area of , it is the Earth's second largest tectonic plate, behind the Paci ...

. This plate boundary, the Aleutian Trench, has been the location of many megathrust earthquakes.

Characteristics

The 1965 Rat Islands earthquake share common features with the

1963 Kuril Islands earthquake Events January * January 1 – Bogle–Chandler case: Commonwealth Scientific and Industrial Research Organisation scientist Dr. Gilbert Bogle and Mrs. Margaret Chandler are found dead (presumed poisoned), in bushland near the Lane Cov ...

and the 1964 Alaska earthquake.

Earthquake

The earthquake was associated with a 600 km long rupture along the plate boundary, based on the distribution of aftershocks. The pattern of energy release suggest the presence of three asperities along the plate interface, each causing a pulse of

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release. Modelling of the tsunami supports the idea that the earthquake consisted of three sub-events, related to three structural 'blocks' within the overriding plate. The main shock was followed by an earthquake of magnitude 7.6 nearly two months later, that triggered a small tsunami. This was not an aftershock, but a

normal fault In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

event within the outer rise of the subducting plate, triggered by the earlier event.

Tsunami

The tsunami had a maximum run-up height of 10.7 m on Shemya Island, 2.0 m at Amchitka Island, 1.6 m at Attu Island and 1.1 m in northern

Kauai Kauai, () anglicized as Kauai ( ), is geologically the second-oldest of the main Hawaiian Islands (after Niʻihau). With an area of 562.3 square miles (1,456.4 km2), it is the fourth-largest of these islands and the 21st largest islan ...

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. It was also observed in

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Mexico Mexico (Spanish language, Spanish: México), officially the United Mexican States, is a List of sovereign states, country in the southern portion of North America. It is borders of Mexico, bordered to the north by the United States; to the so ...

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...

and eastern

Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-ei ...

Damage

Flooding from the tsunami caused $10,000 worth of damage on

Amchitka Island Amchitka (; ale, Amchixtax̂; russian: Амчитка) is a volcanic, tectonically unstable and uninhabited island in the Rat Islands group of the Aleutian Islands in southwest Alaska. It is part of the Alaska Maritime National Wildlife Ref ...

. Minor damage from the earthquake was recorded on both Attu and Shemya islands in the form of cracks in runways.

References

External links

* {{Earthquakes in Alaska 1965 in Alaska Megathrust earthquakes in Alaska

1965 tsunamis