A physical stratigraphy model for seismic microzonation of the Central Archaeological Area of Rome (Italy)

A reliable litho-technical model for seismic microzonation requires a robust understanding of the subsoil architecture, that is essential to extrapolate in the space geognostic data that are often sparse. This paper presents the application to the level 1 seismic microzonation of the Central Archaeological Area of Rome of a complete methodological approach implementing physical stratigraphy concepts into an integrated analysis of a subsurface dataset. Particular emphasis has been placed on the reconstruction of buried geometries, distribution of lithofacies, and stacking pattern of geological bodies, which can control local seismic response. The spatial distribution of paleovalley infill and interfluves domains in the subsoil was reconstructed, which in virtue of their peculiar stratigraphy and morphology may determine 1D and 2D resonance effects. The summation of amplification effects due to the thick anthropogenic layer allowed to outline five stable zones prone to ground motion amplification, of which the most critical coincide with the narrow and deep infill of recent valleys. Potentially less prone to valley effects is the Middle Pleistocene paleovalley infill in the subsurface of the northern and eastern Palatine hill. Finally, the less hazardous zones correspond to the ancient, multilayered volcano-sedimentary interfluves separating the paleovalleys.