Insights into bedrock paleomorphology and linear dynamic soil properties of the Cassino intermontane basin (Central Italy)

Abstract

Seismic amplifications are dictated by the depth of the bedrock and the stratigraphy and dynamic properties of the soil deposits. Quantifying these properties, together with their uncertainty, is a necessary task to perform a reliable assessment of the seismic risk at an urban scale. In this paper, a multidisciplinary analysis is presented, where information of different nature is combined. Borehole logs, geophysical, geological and geotechnical surveys are interpreted with the aid of analytical, numerical and geostatistical techniques to characterise the complex shape of the bedrock and the linear dynamic properties of the sedimentary deposits filling the Cassino basin, a Quaternary intermontane basin located in central Italy. The regional and local seismic hazard is firstly identified with geological surveys that reveal an active seismogenic fault capable of producing earthquakes with estimated magnitudes up to 6.5. Boreholes reaching depths variable up to a maximum of 180 meters and microtremor measurements, revealing the sharp impedance contrast at the transition between the sedimentary/arenaceous bedrock and the soft Quaternary infilling, are combined to identify the depth of the bedrock and the linear dynamic properties of soil deposits. These are one of the key factors governing the propagation to the ground level of seismic waves, and their assessment represents the first step for the seismic hazard characterisation of the plain.