Improving seismic hazard approaches for critical infrastructures: a pilot study in the Po Plain

Paper describes the extensive work done in the SIGMA project, aimed at improving
knowledge on data, methods and tools to better quantify uncertainties in seismic hazard
assessment (SHA). The authors cooperated in the study of potential faults and geological
structures, earthquake catalogues, selection of ground motion prediction equations, and methods
for site effect evaluation suitable for SHA. All the contributions merged into a probabilistic
seismic hazard study conducted for three representative sites of the Po Plainin Northern Italy. Po
Plain is a low-to-moderate seismicity region, characterized by some critical features, such as
blind faulting and deep alluvium sediments, and by scarcity of strong motion data; these sources
of uncertainties in seismic hazard estimation are common to other low seismicity areas around
the world. Within SIGMA, special care was devoted to: (a) the use of the single station sigma
approach inside the probabilistic SHA, (b) the comparative use of generalized attenuation
functions to evaluate the hazard contribution of composite fault systems, and (c) the study of the
epistemic uncertainties at play when different modelling approaches to site effects are used.