3D Geophysical Model of the Vajont Rockslide from Seismic and Geoelectric Surveys

The Vajont rockslide represents the most catastrophic massive failure of a mountain slope ever reported in historical times. The reconstruction of the geometry and of some key physical properties represents a major step forward in the understanding of the slide mechanism and of the collapse dynamics. The landslide body and the surroundings were then targeted with a large 3D geophysical campaign aimed to define the seismic and the electrical properties of the various geological units comprising its body. Data analysis and interpretation was constrained by a series of additional seismic and electrical measurements collected on the outcropping rocks below the village of Casso. The larger values of P- and S-wave velocities as well as terrain resistivity appear to be located in the eastern block while in the western one these parameters are much lower values. These variations in the rock mass coherency are somewhat related to the larger stress field acting on the western block before and during the failure. Furthermore the slide displacement of the eastern block is lower than the western one due a small amount of rotation during the collapse.