Friday, April 06, 2018

Two interesting landslides triggered by the Papua New Guinea earthquake

 by Dave Petley,
April 4, 2018

Two of the more interesting landslides from the Papua New Guinea earthquake
Slowly improved satellite imagery is becoming available showing the landslides triggered by the Papua New Guinea earthquake.
 This event seems to have been quite efficient at generating large landslides, some of which appear to be quite interesting.
I thought it would be useful to highlight two of these, although there are many more.
A very large avalanche type failure, with a displaced but intact block
On 20th March, Planet Labs was able to image beautifully a very interesting landslide located at -6.14, 142.91 :-
Planet Labs image of the large avalanche type failure from the Papua New Guinea earthquake.

This slide is about 3 km long and the track is over 500 m wide (the headscarp area is about 1 km wide).
This landslide is located southeast of Komo Station.
 The main part of the landslide appears to be a flow type failure, presumably consisting if a fragmented block from the hear scarp, with some debris entrainment along the track.
 It appears to me that there is another very large displaced block stalled in the headscarp area (note the raft of displaced but intact trees).
 The rear scarp if this is block is orientated roughly east – west, with considerably more displacement towards the east end.  It is likely that this block will progressively degrade over the tears ahead, although a more rapid failure cannot be eliminated.
I suspect that the watercourse downstream from this landslide is going to suffer a large input of sediment in the coming years.
A large, complex flow type failure
Further to the west is a very complex area of extensive landslides, in the area of -6.02, 142.62:-
Planet Labs image dated 31st March 2018 showing extensive landsliding induced by the Papua New Guinea earthquake.
This image appears to show very extensive landsliding around the drainage system.  In the centre of the image is a much more complex and interesting landslide, with dimensions of >2 km by >1 km.  Downstream from this slide there appears to be a very wide swathe of damage around the river, extending for up to about 4 km down to the main channel.
It is not clear to me as to whether this was a part of the landslide itself or erosion from an outbreak flood when a landslide dam breached.

Planet Team (2017). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA.

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