23 November 2017
Landslides from the Iran-Iraq earthquake
The M=7.3 12th November Iran-Iraq earthquake is now known to have killed over 450 people. As the story slowly drops from the news, some information is emerging about landslides triggered by the earthquake. Unfortunately there is still considerable confusion, and interestingly at times it seems that the landslides are being interpreted as the fault rupture. Once again I am reminded that the understanding of landslides in the earthquake community is not as strong as would be ideal.
The largest set of landslides appears to have occurred close to the village of Mela Kabod in Iran, at about 34.535, 45.898. There are some images of this rather complex set of landslides on the Iranian media and on Twitter. Ehsan Kosari tweeted this set of images of the scarps from the landslides:-
Planet Labs have a good set of images of this area, which pick up these landslides well. This is an image showing the area before the earthquake (collected on the day of he event in fact):
The slope goes downwards towards the southwest corner. And this image, taken on 15th November, shows the aftermath:-
The image clearly shows an array of tension crack running northwest to southeast towards the top of the slope, and there is extensive slip in the upper portion of the slope as well. These appear to be lateral spreading type landslides with quite limited slip (though the resolution of the images is 3 metres, so those tension cracks must be quite large). I think there is also some evidence of rockfalls on the images too, but the extent seems quite limited. Sanaz Vajedian tweeted an analysis that suggests about 7 m of displacement – that looks about right to me.
Planet Team (2017). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://api.planet.com