30 Oct 2020

30 Oct 2020

Review status: this preprint is currently under review for the journal ESurf.

Short communication: Runout of rock avalanches limited by basal friction but controlled by fragmentation

Øystein T. Haug1,2, Matthias Rosenau1, Michael Rudolf1, Karen Leever1,3, and Onno Oncken1 Øystein T. Haug et al.
  • 1GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Telegrafenberg, 14473 Potsdam, Germany
  • 2Njord center, Department of Geosciences, University of Oslo, PO Box 1048, 0316 Oslo, Norway
  • 3Van Hall Larenstein University of Applied Sciences, Larensteinselaan 26a, 6882 Velp, The Netherlands

Abstract. Rock avalanches display exceptionally long runouts, which are found to correlate with their volume and attributed to size dependent dynamic lowering of the effective basal friction. However, even for similar volumes, runouts are seen to span several orders of magnitude suggesting additional controlling factors. Here, we here analyse experiments with analogue models of rock avalanches aimed at testing the role of dynamic fragmentation. We show that for a fixed low basal friction, the runout of experimental rock avalanches varies over two orders of magnitude and is determined by their degree of fragmentation while the basal friction acts only as an upper limiter. We interpret the runout's dependence on fragmentation to be controlled by the competition between mobility enhancing spreading and energy consuming internal friction. We formalize this competition into a scaling law based on energy conservation which shows that variation in the degree of fragmentation can explain the large variation in runout of rock avalanches seen in nature.

Øystein T. Haug et al.

Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

Øystein T. Haug et al.

Data sets

Laboratory model data from experiments on fragmenting analogue rock avalanches Øystein T. Haug, Matthias Rosenau, Michael Rudolf, Karen Leever, and Onno Oncken

Øystein T. Haug et al.


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Short summary
We investigate laboratory scale, sliding analogue rock masses (avalanches) undergoing fragmentation. We find that travel distance (runout) is controlled by the degree of fragmentation. Fragmentation increases mobility of the rock mass but on the other hand consumes energy and therefore reduces the runout from its theoretically given maximum dictated by the friction at its base. We derive a mathematical formulation describing this interplay and which may useful for hazard assessment.