par- 6 janvier 2017
Sujet de la thèse : Landslides triggering in the Colca valley, Peru ; Satellite optical imagery & in situ monitoring
Doctorante : Noélie BONTEMPS
Encadrants : Pascal LACROIX, Eric LAROSE
Landslides cause almost 10000 victims every year [Petley, 2012] triggered by four main forcings : (1) earthquakes, (2) precipitations, (3) fluvial erosion, (4) human activity. The relative part of each of these forcings to the landslide dynamics is poorly constrained in seismic active regions where their effects can be interdependent. The Colca valley, South Peru, offer an exceptional site for studying this dynamics, with seasonal rainfalls and strong seismic activity [Lacroix et al., 2014]. Ten active landslides situated along the Colca river were recently detected in the valley. Thanks to archives of optical satellites images (Landsat, SPOT, ASTER, Pléiades) and aerial imagery, 60 years of monitoring are available on the area (1955-2015). This thesis will focus on identifying the relative contribution of the sismotectonic, rainfalls and fluvial forcings in landslide dynamics thanks to the processing of the time-series of deformation of all of the landslides over 60 years. A specific focus will be held on the dynamics of the fluvial erosion and the rapid lateral motions of the Colca river as a result of the concurrence between landslides situated on opposite sides of the river. In a second part, the objective will focus on understanding the mechanics of the Maca landslide situated in the Colca valley, during earthquakes and/or rainfalls. This landslide is instrumented since 2015 with GPS stations and seismological arrays. These data will be processed to study the relations between the forcings, damage of the unstable mass, and its deformation.
Lacroix, P., H. Perfettini, E. Taipe, and B. Guillier (2014), Co- and Postseismic motion of a landslide ; observations, modelling and analogy with tectonic faults, Geophys. Res. Lett., 41, 6676–6680
Petley, D. (2012), Global patterns of loss of life from landslides. Geology, 40, 927–930.
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