18 December 2009
There were two landslide sessions at AGU today, both in the afternoon. This was the part of the meeting about which I was most excited, but sadly to be honest the reality did not meet my expectations. I won’t write about all of the talks here, just a selected few.
First up was Bruce Malamud, who talked about the statistics of landslide clusters. This is great work, showing the remarkable similarity between landslide distributions for different multi-landslide events from different areas with different triggers. Helpfully he sumarised the ket implications of this work:
• It provides thae basis for a multi-landslide magnitude scale (like the Richter scale for earthquakes;
• The average landslide area in a multi-landslide event appears to be about 3000 square metres;
• It is at least theoretically possible to determine a volume of sediment production based on a volume area relationship;
• If large landslides arfe preserved in the landscape it shoukd be possible to determine the number of landslides that have been “lost” from erosion (turned out to be >99% in both Japan and Italy)
Interestingly, rockfalls have a very different statistical distribution – I wonder why.
Next up was Colin Stark, who tried to explain aspects of this distribution, and in particular the so-called “roll-over” component (basically there are fewer small slides than one would expect) but building a model of rupture propagation. This was interesting for two reasons. First, the model makes some assumptions about failure that cause concern (but this may have been misunderstanding; second, he came over as being exceptionally unsure of his own model, which was a little odd. The model appears to me to make some predictions that are very testable indeed – so this should evolve quickly.
Larsen, Montgomery and Korup gave a really interesting paper on the role of materials in controlling volume –area scaling for landslides. They challenged recent papers that have suggested that this scaling is independent of material, showing that in fact the scaling is very different from soil than for rock.
The final paper that I want to mention here was by Goren on the absolutely amazing Heart Mountain landslide. This will be the subject of a future post – but basically she was talked about the mechanics of this landslide – surely the largest terrestrial failure of all time! Wow!