Assessing the accuracy of shear-wave profiling at urban sites: the case of Rome (Italy)

This study investigates the effectiveness and complementarity of different seismic methods for shear wave velocity (Vs) profiling in complex urban settings. Focusing on historical areas of Rome, where subsurface conditions are deeply influenced by anthropogenic layers and archaeological constraints, we applied a combination of downhole testing, active and passive surface wave analysis, and HVSR techniques. Each method was critically evaluated in terms of resolution, uncertainty, and depth coverage, particularly in relation to urban constraints such as limited acquisition space and cultural noise. Special emphasis was placed on characterizing deeper stratigraphic horizons that are typically inaccessible with standard borehole investigations, and which are essential for seismic response analyses. Integrated processing and joint inversion approaches were tested to enhance consistency across methods and improve reliability at different depth ranges. The study also highlights the role of low-frequency techniques in overcoming limitations imposed by urban infrastructure and thick fill layers. Our findings underscore the necessity of a multi-method approach to capture the complexity of the subsurface in heritage cities, allowing for robust Vs modeling even where conventional investigations fall short.