Lacroix Pascal. (2016). Landslides triggered by the Gorkha earthquake in the Langtang valley, volumes and initiation processes. Earth Planets and Space, 68, p. art. 46 [10 p.]. ISSN 1880-5981.
Titre du document
Landslides triggered by the Gorkha earthquake in the Langtang valley, volumes and initiation processes
Earth Planets and Space, 2016,
68, p. art. 46 [10 p.] ISSN 1880-5981
The Gorkha earthquake (Nepal, 2015, M-w 7.9) triggered many landslides. The most catastrophic mass movement was a debris avalanche that buried several villages in the Langtang valley. In this study, questions are raised about its volume and initiation. I investigate the possibility of high-resolution digital surface models computed from tri-stereo SPOT6/7 images to resolve this issue. This high-resolution dataset enables me to derive an inventory of 160 landslides triggered by this earthquake. I analyze the source of errors and estimate the uncertainties in the landslide volumes. The vegetation prevents to correctly estimate the volumes of landslides that occured in vegetated areas. However, I evaluate the volume and thickness of 73 landslides developing in vegetated-free areas, showing a power law between their surface areas and volumes with exponent of 1.20. Accumulations and depletion volumes are also well constrained for larger landslides, and I find that the main debris avalanches accumulated 6.95 x 10(6) m(3) of deposits in the valley with thicknesses reaching 60 m, and 9.66 x 10(6) m(3) in the glaciated part above 5000 m asl. The large amount of sediments is explained by an initiation of the debris avalanche due to serac falls and snow avalanches from five separate places between 6800 and 7200 m asl over 3 km length.
