Extending the Usefulness of Seismic Hazard Studies

A seismic hazard study was performed and published in the Bulletin of the Seismological Society of America by Boschi, Gasperini, and Mulargia in 1995. The application of statistical modeling to the independently defined 54 Italian seismotectonic regions led to the result that two regions had an estimated probability of occurrence for an M ≥ 5.9 event close to 1.0 in the following five years. These were the l’Aquila region and southeastern Sicily. This forecast was dramatically verified on April 2009 at l'Aquila. in spite of the fact that first author has since then been in charge of the leading responsibility for seismic risk in Italy, and of the persistence of an earthquake swarm, no practical action was taken. This appears as a solid proof of the lack practical utility of seismic hazard studies, which can never reach a reliability sufficient to order a disruption of everyday life. Hazard studies must therefore be retargeted to guide seismic vulnerability studies at the level of single buildings, the only ones really capable to reduce seismic destruction.