Pseudo-3D Seismic Tomography Approach on a Tuff Cliff in the Sorrento Peninsula, Italy.

The studied area is located in the Sorrento Peninsula, a major Quaternary morphostructural unit of the western flank of Southern Apennines. The peninsula forms a narrow and elevated mountain range that separates two major embayments of the eastern Tyrrhenian margin and is characterized generally by a carbonate bedrock capped by pyroclastic deposits (i.e. "Campania Ignimbrite"), originated from the Campi Flegrei volcanic district. The occurrence of steep slopes and the high relief energy of the area, along with the marine erosion at the base of the coastal cliff creates favourable conditions for the occurrence of a generalized instability of the slopes that is manifested by tuff rock falls as prevailing landslide phenomena. Prediction of such landslides type is difficult if not accompanied by accurate hydrogeologic and geotechnical monitoring and assessment. Often, the presence of pervasive fracturing and cavities in tuff deposit can cause instability and rock falls. Because of 2D-3D cliff effect, we don't apply the standard seismic acquisition geometry.. Therefore, we applied a particular seismic geometry to detect this specific site. A non linear seismic inversion was used to obtain 2D models. They allowed to build a pseudo 3D Vp/Vs ratio. The 3D Vp/Vs ratio pseudosection showed anomaly zones in the investigated rock. We identified an area with a low Vp/Vs value that we associate with a medium having a lower porosity or in dryer condition respect to the surrounding material.