Numerical modelling of site effects in the Palatine Hill, Roman Forum, and Coliseum Archaeological Area

Historical sources report that Rome has experienced considerable earthquake ground motion in the past, even though it is quite far from high-magnitude seismogenic sources.Damage distribution seems to be predominantly controlled by ground shaking amplification related to local soil conditions. In this context a multidisciplinary research project has been conducted to determine the seismic microzonation of the Central Archaeological Area of Rome, which includes the Palatine Hill, Roman Forum, and Coliseum. In particular, the present paper details the results of one and bi-dimensional site response analyses carried out within this project, focusing discussion on representative cross-sections. The peculiarity of this work stems from the fact that it represents the first systematic study on the seismic site response of Rome’s historical centre based on a robust subsoilmodel which integrates a large amount of available and original geological, geophysical and geotechnical data. Investigation of the physical phenomena responsible for site effects shows that ground motion distribution is mainly controlled by 1D resonance phenomena and 2D effects associated with soft alluvial valleys bordering the Palatine Hill, a deep paleo-valley and, to a lesser extent, topography and the morphology of anthropogenic deposits. The analyses show maximum amplification factors, defined in terms of Housner Intensity, as high as 1.4–1.8 over the period range of 0.1–1.0 s. Such values can be significantly relevant for the monumental and archaeological heritage of this area, as many are highly vulnerable due to their great age.