2024 年 10 巻 17 号 p. 597-602
On November 9, 2022, two earthquakes of magnitude 5.5 and 5.2 respectively, struck off Italian Adriatic coast with a one-minute delay, but caused no serious damage or injuries. The epicenter of the quake was 35 km offshore from Pesaro, a seaside city in the eastern Marche region, at a depth of 7 km. The two earthquakes ruptured a well-known fault in the buried thrust front of the Northern Apennines. The size and architecture of these faults suggest they could generate even larger earthquakes. Even though no relevant damage observations have been reported after the event as verified by an ad-hoc on-site reconnaissance, 4 recording stations located among the cities of Ancona and Senigallia recorded a horizontal peak ground acceleration higher than 0.1 g. This value is usually adopted as a threshold to discriminate the triggering of seismic-induced soil liquefaction, as well as a magnitude of 5 is considered the lower value able to trigger liquefaction. Moreover, parts of the Marche and Emilia Romagna coast are characterized by saturated granular soil deposits and experienced in the past several liquefaction manifestations. Reports of such historical earthquakes often mention local hydrogeological alteration, surface manifestations/deformation, and liquefaction phenomena (e.g., Rimini’s earthquakes, 1875 and 1916, and the Senigallia’s earthquake, 1930). Therefore, the seismic event of the 9th of November 2022 represents an interesting case study to assess the effectiveness of current soil liquefaction methods based on semi-empirical charts for correctly predicting the non-occurrence of soil liquefaction manifestations. The study assesses the safety against liquefaction for the considered seismic event at a specific site of Senigallia where liquefiable deposits have been detected and adequate soil characterization is available through in-situ tests.
