Subsurface profiling of buried valleys in central alps (northern Italy) using HVSR single-station passive seismic

Active and passive seismic techniques permit to draw images of relevant buried morphologies in mountainous areas. Here we apply the Horizontal-to-Vertical Spectral Ratio (HVSR) technique shape a valley core Italian Central Alps, at confluence among fault-controlled Valtellina, Valchiavenna Lake Como depressions (“Colico knot”). Twenty-three single-station, ambient-noise measurements were acquired site-specific fundamental frequency f0 was obtained by computing HVSR 0.5 Hz 5 band. Shear wave velocity (Vs)-versus-depth profiles computed from inversion curves, under assumption 1D structure. To limit uncertainty, results calibrated comparison with data two sources: 1) comparable setting site where estimates Vs for basement cover sediments available; 2) borehole logs which crossed above metamorphic bedrock Colico knot site. Independent used constrain best fit experimental peaks site, terms amplitude, thus retrieving information about variations related versus unconformity. A SW-NE elongated trough, as deep 150 m below sea-level up 2 km wide drawn present-day Adda depression South. The morphology this abandoned course river is controlled active deep-seated gravitational slope deformation along adjacent mountain slope. before Last Glacial Maximum (latest Pleistocene), plausibly owing narrowing uplift induced deformation. In fact, LGM glacier reshaped slopes watershed that separates present post-Glacial paleo-Adda trough.