Cadre structural et risques géologiques étudiés à l’aide de l’imagerie spatiale: la région du Colca (Andes du sud Pérou)

Abstract

Geologycal analysis from remote sensing sata (Spot and Landsat) in Arequipa area and Colca valley (southern Peru) permits to characterize and to locate three different type of natural hazards: the seismic, volcanic and landslide risks. Seismic risk is associated with numerous faults . The mayor fault system is oriented N070°E to N135°E and affected by a sinistral strike slip-motion. It is associated with minor N055°E opened fractures; these faults may be reactivated by earthquakes. The major fault systems strikes N135°E and forms releasing bends including the N055°E open fractures which may give way to the Quaternary volcanism. At last, the volcanic risk is evidenced by the present-day eruptive process of Nevado Sabancaya and the potential activity of Misti volcano (close to Arequipa). The landslide risk is mainly in the alluvial-lacustrine clays along the steep slopes of the Colca valley.