Identification of realistic geotechnical subsoil models from the integration of HVSR data and 2D site response analyses

The seismic risk assessment should rely on the accurate prediction of the seismic site response of the area of interest, which is strictly related to the proper definition of the geotechnical subsoil model. Especially for natural slopes characterized by buried morphologies, for which the vertical and lateral heterogeneity of the subsoil setting may exacerbate the seismic site amplification, the identification of the geotechnical subsoil model may become challenging. Indeed, when dealing with not well-characterized sites, noninvasive and expeditive site investigations, such as seismic seismic ambient noise measurements and geophysical surveys, could be useful for a first interpretation of preliminary geotechnical subsoil models. Recently, a relatively simple and expeditive methodological procedure, based on the joint interpretation of non-invasive geophysical investigations and parametric 2D numerical analyses of the seismic site response, has been proposed to develop reliable geotechnical subsoil models. The paper illustrates an application of the procedure to identify the preliminary subsoil models of an area characterized by complex topography and subsoil conditions. The site studied is the Costa del Canneto slope (Ferrandina, Matera) in Southern Italy, characterized by uneven topography and complex subsoil setting, potentially including lithological bodies of uncertain morphology causing geological and geomechanical heterogeneity. The procedure proves to be a useful tool to reduce the uncertainties associated with the presence of complex subsoil settings, including potential buried morphologies. Indeed, among several hypothesized geotechnical models, only for few of them the numerical analyses provide amplification profiles of the fundamental frequency reasonably comparable with data from seismic ambient noise measurements, allowing to reduce the number of possible slope models. These findings can be adopted to guide the design of additional in-situ geotechnical investigations, needed to better characterize the stratigraphy of the area and constrain the geometry of the expected buried morphologies.