COMBINED GEOPHYSICAL METHODS FOR LANDSLIDE RESIDUAL RISK ASSESSMENT: THE POMARICO LANDSLIDE (BASILICATA, SOUTHERN ITALY) CASE STUDY

Abstract:

On the 25^th and 29^th of January 2019, a large landslide destroyed an important part of the town of Pomarico, in Basilicata region (Southern Italy). In order to assess the landslide residual risk in the urban area close to the crown of the landslide, Electrical Resistivity Tomography (ERT), Multi-Channel Analysis of Surface Waves (MASW) and Seismic Refraction Tomography (SRT) have been applied. Geological and geomorphological investigations were also carried out to provide a detailed description of the geomorphological setting of the area.

The joint analysis of the geophysical results, compared with geological and geomorphological data, allowed us to identify the existence of predisposing and triggering elements that could favour future sliding.

In particular, detailed information about the stratigraphic setting and the post-failure stability conditions changes in the sandy subsoil were obtained. The geophysical analyses highlighted the multiple old degraded scarps, developed over the time, and provided information on the decompression state of the different areas of the landslide crown. They also allowed the identification of natural and anthropogenic caves, mainly developed in well-cemented layers of sands.

The integration of the different geophysical methods helped to increase the detail of information in a complex environment, such as urban areas, and to overcome the limitations of each single method.