1 December 2018

First images of slope failures triggered by the M=7.0 Alaska earthquake

Posted by Dave Petley

First images of slope failures triggered by the M=7.0 Alaska earthquake

The M=7.0 Alaska earthquake on 30th November 2018 was sufficiently large to trigger some slope failures, even though it was comparatively deep (41 km).  Such an earthquake would be expected to generate shaking over a large area, but probably with reasonably modest peak ground accelerations.  The USGS ground failure model suggests that only a small area might have been subjected to slope failures, but much of the area affected had limited potential for large-scale landslides due to the low relief topography:-

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USGS map of landslide potential from the M=7.0 Alaska earthquake

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There may be some landslides to the east of the epicentre in the rugged terrain there.  Some images of slope failures have started to emerge though.  @AOC-Security has tweeted this image of a lateral spread affecting a road embankment on Vine Road in Wasilla:-

Alaska Earthquake

An apparent lateral spread, triggered by the Alaska Earthquake affecting Vine Road in Wasilla . Image tweeted by @AOC-Security

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Meanwhile David Ruffini has tweeted an image of the same feature in daylight:-

Alaska Earthquake

An apparent lateral spread, triggered by the Alaska Earthquake affecting Vine Road in Wasilla . Image tweeted by David Ruffini.

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This lateral spread has been caught in a spectacular airborne image by Marc Lester:-

Alaska earthquake

A sensational image by Marc Lester showing a lateral spread triggered by the Alaska Earthquake.

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Josh Bierma tweeted an image of another apparent lateral spread affecting a road:-

Alaska Earthquake

A lateral spread, triggered by the Alaska earthquake, affecting a highway. Image tweeted by Josh Bierma

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That event could have been far worse for the occupants of the car.  And Ryan Hobbs tweeted an image of yet another such lateral spread affecting a highway:-

Alaska earthquake

A lateral spead triggered by the Alaska earthquake. Image tweeted by Ryan Hobbs.

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Ryan Hobbs has also tweeted an image of rockfalls affecting a road in the earthquake affected area:-

Alaska earthquake

Rockfalls triggered by the Alaska earthquake. Image tweeted by Ryan Hobbs.

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