VOLCANO MADNESS: [Geology2] An emerging crisis? Valley blocking landslides in PNG

Wednesday, February 28, 2018

[Geology2] An emerging crisis? Valley blocking landslides in PNG

An emerging crisis? Valley blocking landslides in the Papua New Guinea highlands

Posted by Dave Petley | 28 February 2018

An emerging crisis? Valley blocking landslides in the Papua New Guinea highlands

The Mw=7.5 earthquake in Papua New Guinea has generated remarkably little international publicity. I noted shortly after the earthquake that landslides are likely to be a significant problem given the nature of the earthquake and the topography. Information is slowly emerging now, and this is increasingly looking like a potential crisis to me. The best data so far has been posted on the Facebook Page of Bernard James McQueen, who appears to be a helicopter pilot (?) from New Zealand, working in Papua New Guinea. He has posted a series of images and two videos – check them out, they make deeply alarming viewing. The videos appear to show very large numbers of very large valley blocking landslides. This is one of the photographs:-

An extremely large planar rockslide in Papua New Guinea. Image posted on Facebook by Bernard James McQueen.

But this is not the only valley blocking landslide – this is a still from one of the videos:-

Papua New Guinea landslide crisis: a still from a video posted on Facebook by Bernard James McQueen.

Satellite imagery of this area is quite difficult to obtain due to cloud cover, but the first images have now been captured by Planet Labs. This covers only a small part of the earthquake affected area, and there is a considerable volume of cloud. But the picture that is emerging is deeply alarming, with huge numbers of landslides, many of which look to be potentially valley blocking. This is the area just to the east of Komo Station:-

Planet Labs image of the a part of the area affected by the earthquake in Papua New Guinea.

Note the large flow-type landslide in the south of the image, and the multiple rockslides elsewhere. Some of these slides appear to be very complex.

This is an exceptionally dangerous situation that needs urgent attention. Papua New Guinea has high rainfall, so quake lakes may develop quickly. Overtopping is extremely hazardous, especially when there are multiple landslide dams. There is an urgent need to evaluate the number and scale of the landslide dams, and the likely assets downstream that could be affected.

The last event on this scale was the 2008 Wenchuan earthquake. In that case over 200 landslide dams needed attention; a feat that stretched even the mighty resources of the Chinese military. The capacity to deal with this in Papua New Guinea is much lower. This feels like a potential crisis to me.