Effects of uncertainties and soil heterogeneity on the seismic response of archaeological areas. A case study

The paper deals with a numerical study aimed at the evaluation of the seismic response of the Central Archaeological Area of Rome including Palatine hill, Roman Forum, and Coliseum. A relevant role is played by buried morphology and mechanical properties of the anthropogenic cover which reaches a thickness of 20 m. This layer is constituted by "dominant masonry" and "dominant infill" zones strongly variable in the space thus exhibiting wide spatial heterogeneity in dynamic properties whose definition is affected by high degree of uncertainty. In order to investigate the effects of the uncertainty in dynamic soil properties of the anthropogenic unit on ground motion at surface, 1D and 2D stochastic analyses were carried out. The numerical results were then compared with those obtained from a standard deterministic model defined by using "average" values of dynamic properties. The influence of uncertainty in shear wave velocity distribution as well as in nonlinear properties (i.e. normalized shear modulus and damping curves) of the anthropogenic cover is highlighted in terms of Housner Intensity amplification factors profiles and acceleration response spectra in representative nodes at surface.