The 1965 Rat Islands earthquake occurred at 05:01 UTC, on 4 February. It had a magnitude of 8.7 and triggered a tsunami of over 10 m on Shemya Island,^[1] but caused very little damage.

Damage

Flooding from the tsunami caused $10,000 worth of damage on Amchitka Island.^[1] Minor damage from the earthquake was recorded on both Attu and Shemya islands in the form of cracks in runways.

Tectonic setting

seismicity]] of Alaska The Rat Islands form part of the Aleutian Islands, a chain of volcanic islands forming an island arc, that results from the subduction of the Pacific Plate beneath the North American Plate. This plate boundary, the Alaska-Aleutian megathrust, has been the location of many megathrust earthquakes.

Characteristics

Earthquake

The earthquake was associated with a 600 km long rupture along the plate boundary, based on the distribution of aftershocks.^[2] The pattern of energy release suggest the presence of three asperities along the plate interface, each causing a pulse of moment 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.^[3]

The main shock was followed by an earthquake of magnitude 7.6 nearly two months later, that triggered a small tsunami.^[4] This was not an aftershock, but a normal fault event within the outer rise of the subducting plate, triggered by the earlier event.^[5]

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, Hawaii. It was also observed in Peru, Ecuador, Mexico, California, Japan and eastern Russia.^[4]

References

pl:Trz sienie ziemi na Alasce (1965) zh:1965