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1965 Rat Islands earthquake

Megathrust earthquake in the Aleutian Islands

Field	Value
title	1965 Rat Islands earthquake
timestamp	1965-02-04 05:01:22
isc-event	859206
anss-url	iscgem859206
local-date
local-time	19:01:22
damage	$10,000
map2	{{Location map	Alaska
relief	1
lat	51.27
long	178.55
mark	Bullseye1.png
marksize	50
position	top
width	260
float	right
caption	}}
magnitude	8.7
depth	30.3 km
location
countries affected	United States (Alaska)
tsunami	10.7 m
intensity

|isc-event = 859206 |anss-url = iscgem859206 |local-date = |local-time = 19:01:22 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, making it one of the largest earthquakes in recorded history, and triggered a tsunami of over 10 m on Shemya Island, but caused very little damage.

Tectonic setting

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 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 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 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.

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

Damage

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

References

(26 October 2009). "Historic Earthquakes Rat Islands, Alaska". United States Geological Survey.
(9 October 1973). "Source mechanism of February 4, 1965, Rat Island earthquake". Journal of Geophysical Research.
(1991). "Rupture process of the February 4, 1965, Rat Islands Earthquake". Journal of Geophysical Research.
(1998). "Tsunamigenic Earthquakes and Their Consequences".
NGDC. "Search result for 1965 Alaska earthquakes".
(January 1972). "Lithospheric normal faulting beneath the Aleutian trench". Physics of the Earth and Planetary Interiors.

Info: Wikipedia Source

This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

1965-in-alaska february-1965 megathrust-earthquakes-in-alaska 1965-earthquakes 1960s-tsunamis rat-islands earthquakes-in-the-aleutian-islands

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