Ground-Motion Observations and Probabilistic Seismic Hazard: Frequently Asked Questions

Observed exceedances of ground-motion intensity from probabilistic seismic hazard analysis (PSHA), in countries where it is used for structural design, spark significant public attention, rekindle scientific debates, and are sometimes discussed in trials about the accountability for structural failures and other earthquake-related losses. This short article addresses, in a question-reply format, some recurring issues and related research findings that should be carefully taken into account by those who author or face these reasonings. It considers Italy as a reference, yet the discussed issues are common to several other countries worldwide and thus may be interesting at an international level. The arguments provided, mainly stemming from the fact that observed cases of exceedance should not necessarily be considered a failure of PSHA, can possibly help in gaining a more informed perception of seismic hazard assessment and structural design as implemented in building codes.