Reconstructing historical seismicity from lake sediments (Lake Laffrey, Western Alps, France) |
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| Authors: | Jé rô me Nomade,Emmanuel Chapron,Marc Desmet,Jean-Louis Reyss,Fabien Arnaud, Vincent Lignier |
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| Affiliation: | Laboratoire de Géodynamique des Chaînes Alpines, UMR CNRS 5025, UniversitéJoseph Fourier, Grenoble, France;;Laboratoire de Géodynamique des Chaînes Alpines, UMR CNRS 5025, Universitéde Savoie, Savoie, France;;Institut des Sciences de la Terre d'Orléans, UMR CNRS 6113, Universitéd'Orléans, Orleans, France;;Geological Institute, ETH Zürich, CH-8092 Zürich, Switzerland;;EDYTEM, UMR CNRS 5204, Universitéde Savoie, Savoie, France;;Laboratoire des Sciences du Climat et de l'Environnement, UMR 1572 CEA-CNRS, Gif/Yvette, France;;Laboratoire Souterrain de Modane, CEA-CNRS, Modane, France |
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| Abstract: | Sediment archives from a mountain lake are used as indicators of seismotectonic activity in the Grenoble area (French western Alps, 45°N). Sedimentological analysis (texture and grain-size characteristics) exhibits several layers resulting from instantaneous deposits in Lake Laffrey: six debris flow events up to 8 cm thick can be attributed to slope failure along the western flank of the basin. Dating with 210Pb and 137Cs gamma counting techniques and the reconnaissance of historical events, provide a constrained age-depth model. Over the last 250 years, five of such debris flow deposits could be related to historical earthquakes of MSK intensities greater than VI over an area of <60 km. One debris flow deposit triggered at the beginning of the last century can be related to an historical landslide possibly triggered by the artificial regulation of the lake level. |
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