A multidisciplinary methodology to reconstruct and assess bedrock effects for seismic risk mitigation: a case study of deep and liquefiable deposits in Italy

This paper presents a comprehensive methodology for reconstructing seismic bedrock and investigating its role in areas where seismic (i.e. amplification) and co-seismic (i.e. liquefaction) effects are expected. Reconstructing seismic bedrock can be challenging, particularly in the presence of deep interfaces. To address this, a field campaign was conducted in 2021 in the municipality of Terre del Reno (Po Plain, Italy), an area characterised by deep and liquefiable deposits and significant damage after the 20 May 2012 Mw 6.1 earthquake and its aftershocks. The newly acquired geophysical dataset comprises 107 single station ambient vibration data points, revealing high-amplitude HVSR curves in the 0.2–1 Hz range. The shear-wave velocity (Vs) profile used for geophysical imaging of the subsoil model incorporated results from available passive and active multichannel seismic arrays, enabling calibration of seismo-stratigraphic models. Additionally, 1D seismo-stratigraphies subjected to 1D modelling supported a parametric analysis useful for investigating uncertainties related to liquefaction triggering. Various synthetic input motions were simulated using the DEEPSOIL code. These results confirmed that the assumed depth of seismic bedrock significantly influences outcomes.