The large landslide of Patigno (Northern Apennines, Italy): geological, geomorphological and geognostic integrated analysis

Geological, geomorphological and geophysics surveys were integrated to highlight the causes, the mechanism and the evolution of the Patigno Landslide, in the Northern Apennines. The geophysical surveys, constrained with stratigraphic-geotechnical data, identify two layers with different P-wave velocities, beside the undisturbed bedrock. The uppermost layer can be considered the landslide body affected by slides and flows reactivations. The lowermost layer is affected by slow displacements, as demonstrated by the instrumental records. The geomorphological survey shows that the Patigno Landslide is made up of many different slide/flow landslides that share an unique slip surface, identified by the seismic surveys. A deep-seated gravitational slope deformation can be inferred for the lowermost layer. The slope instability can be related mainly to the weak mechanical behavior of the rocks. Nowadays, the triggering factors are mainly the under-cutting at the toe of the landslide by the Gordana River and the heavy and/or intense rainfalls, as testified by the dendrogeomorphological survey.