The contribution of “silent” faults to the seismic hazard of the northern Adriatic Sea

Abstract There is a difference in the seismogenic zonation used for seismic hazard assessment of ordinary buildings and that considered for critical facilities, because different levels of exceedence probability are taken into account. Consequently, in the second case tectonic structures with a low, or very low, likelihood of activation also need attention. The key factor in seismogenic zonation for seismic hazard assessment is investigated here considering some seismically undocumented faults of the northern Adriatic Sea area. Seismic hazard is evaluated for two constructions located around Trieste and close to the sea: an ordinary building and a critical facility. The results clearly show that the two constructions should be designed with quite a different level of expected ground motion in mind. Part of the difference, in the computation of the critical facility, is determined by the introduction of some faults without documented seismicity.

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