Effets de site, endommagement et érosion des pentes dans les zones épicentrales des chaînes de montagnes actives

Landslides are a major natural hazard that cause significant damages and casualties to people. Earthquakes are one of their main triggers in active mountain belts. In epicentral area, the passage of seismic-waves that disrupt the stress-field, leads the slope stability threshold to be exceeded. Co-seismic slope failure probability thus depends on complex interactions between the ground-motion and the slope geology and geometry. A few seismic data are available on mountain slopes and the resolution of ground-motion models is generally low. Yet strong variation of ground-motion from one ridge to another can be felt due to site effects. We document site effects across topography and show the complexity of slope responses to earthquakes using a seismic network set across a Taiwanese ridge. Six broadband seismometers were set along the profile of this 3km wide ridge. From March 2015 to June 2016, more than 2200 earthquakes (magnitude Ml>3 and hypocentral distance3, distance hypocentrale