Measurements of shear wave velocities for seismic and volcanic hazard assessment in urban areas

Detailed Vs profiles with Depth can be obtained in urban areas from the nonlinear inversion with hedgehog method of the Raileigh waves group velocity dispersion curves of the fundamental mode extracted with the FTAN method from the recorded signal of active seismic experiments at a single station. Recently, the approach has been applied to cross correlations of long time series of ambient seismic noise as they have been demonstrated to recover surface wave dispersion (Green function) over a broad range of distances. We present some examples of FTAN measurements, for both active and passive experiments, performed in the highly noisy urban area of Napoli, with the definition of Vs profiles to depths of 2 km. Such examples aim to show the successful application of the proposed approach for the mitigation of both seismic and volcanic risk in that stratigraphies, blind because of unaccessible outcrops in densely urbanized areas, can be reliably reconstructed.