Estimating rockfall frequency in a mountain limestone cliff using terrestrial laser scanner

Estimation de la fréquence des éboulements dans une falaise calcaire de montagne par scanner laser terrestre

A Guerin (1) , J-P Rossetti (1) , D Hantz (1) , M Jaboyedoff (2)

1 ISTerre - Institut des Sciences de la Terre
2 Institute of Earth Sciences [Lausanne]

Terrestrial laser scanner has been used to detect rockfalls which occurred in a high rock wall of the Subalpine Chains, from a survey station located up to 900 m from the cliff. Using a threshold of 0.1 m in term of distance variation, 344 rockfalls larger than 0.05 m 3 have been detected for a period of 1180 days, in a rock wall of width 750 m and height 200 m. The complementary cumulative distribution of the rockfall volume is well fitted by a power law, with an exponent b of 0.75 ± 0.04. In order to compare the rockfall frequencies in different geological contexts, a rockfall activity parameter has been considered, which is the number of rockfalls larger than a given volume, which occur per century and per hm 2. For the thinly bedded limestone making the cliff surveyed, the number of rockfalls larger than 1 m 3 is 0.85 rockfalls per year and per hm 2. It is two orders of magnitude higher than the number obtained for massive limestone cliffs of the Subalpine Chains in the Grenoble area.

Domains: Sciences of the Universe [physics]

A Guerin, J-P Rossetti, D Hantz, M Jaboyedoff. Estimating rockfall frequency in a mountain limestone cliff using terrestrial laser scanner. [Research Report] Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IRD, Univ. Gustave Eiffel, ISTerre, 38000 Grenoble, France. 2013. ⟨insu-03598668⟩