Seismic Characterization by Inversion of HVSR Data to Improve Geological Modelling

An application of HVSR inversion is presented in order to verify the effectiveness of this technique for purposes of geological reconstruction of the subsoil finalized to studies of seismic microzonation of heavily urbanized areas, where few stratigraphic and geophysical constraints are available and most of the information are derived from the geological maps. In such cases the uncertainty of the results is is enhanced by doubts on the nature of the H/V peaks, not always caused by stratigraphic discontinuities, and to the subjective choices done especially in the step of signal preprocessing. The investigated area (Altavilla Milicia, Sicily) includes the town center and the adjacent coastal plain, characterized mainly by outcrops of marine terraces and continental Pleistocene deposits that do not indicate directly the oldest geological formations, which, however, outcrop in the surrounding areas. However in order to constrain the inversion of the HVSR curves we uses only the detailed knowledge of the geological formations outcropping in the surrounding area and of the tectonic history, together with the typical seismic velocity of the formation outcropping in the area. In spite of this two geological sections have been constructed, showing the main pattern of geological formations and tectonic structures.