We present a Probabilistic Fault Displacement Hazard Analysis (PFDHA) for a strategic dam located in the Upper Tiber Valley (Northern Apennines of Italy) claimed to be sited on a supposed capable fault (Montedoglio fault). We verify the seismic capability of the Montedoglio fault through detailed geological and geophysical analyses. We find no evidence for considering the Montedoglio fault as an active and capable structure, the fault being constituted by a system of discontinuous parallel faults, apparently inactive since more than 56 ± 3 ka, and likely unable to nucleate strong surface rupturing earthquakes. Since the dam lies on the hanging wall of the closest major active fault of the area (Anghiari normal fault, ∼1.5 km away), we investigate the likelihood of having distributed faulting at the dam's site in case of a strong surface-rupturing earthquake occurring on the Anghiari fault. We apply a probabilistic approach to obtain hazard curves of exceedance of vertical displacement at the dam's site for different rupture scenarios. We show that the mean hazard curve is always below an annual frequency of exceedance of 1 × 10−5, corresponding to displacement values below 1 cm over 100,000 years of return period. The study highlights several weaknesses and uncertainties in using PFDHA with state-of-the-art models, suggesting the need for improvements to enhance their applicability in earthquake engineering geology practice.

中文翻译：

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概率断层位移 延伸环境中的危害分析：在战略 Dam 中的应用和方法学意义


我们提出了位于台伯河上游河域（意大利北亚平宁山脉）的一座战略大坝的概率断层位移危害分析 （PFDHA），该大坝声称位于假定的有能力的断层（Montedoglio 断层）上。我们通过详细的地质和地球物理分析来验证 Montedoglio 断层的抗震能力。我们没有发现任何证据证明将蒙特多利奥断层视为一个活跃且有能力的结构，该断层由一个不连续的平行断层系统构成，显然在超过 56 ± 3 ka 后处于不活跃状态，并且可能无法成核强烈的地表破裂地震。由于大坝位于该地区最近的主要活动断层（Anghiari 正常断层，约 1.5 公里外）的悬盘上，我们调查了在 Anghiari 断层上发生强烈地表破裂地震的情况下，大坝所在地出现分布式断层的可能性。我们应用概率方法来获得不同破裂情况下大坝现场垂直位移超过的风险曲线。我们表明，平均风险曲线始终低于 1 × 10-5 的年超标频率，对应于在 100,000 年的重现期内低于 1 cm 的位移值。该研究强调了将 PFDHA 与最先进模型一起使用的几个弱点和不确定性，表明需要改进以提高它们在地震工程地质实践中的适用性。