Il terremoto del settembre 1924 in Mar Ligure e la sua relazione con il recente evento sismico a Bargagli (Genova, settembre 2022) / The earthquake of September 1924 in the Ligurian Sea and its relationship with the recent seismic event in Bargagli (Genoa, Italy, September 2022)

Abstract

On September 22, 2022 the Bargagli area, located about 10 kilometers away from Genoa, was affected by a series of earthquakes of which the largest was that of 15.39 (local time), of magnitude Mw 4.0. The event was felt in a very large area and caused minor damage to a church and a cemetery. A few smaller magnitude tremors followed, mainly clustered in the first few days after the main event. The peculiarity of this seismic crisis is that it occurred in an area not previously affected by earthquakes of that magnitude, at least according to the information contained in the historical and instrumental catalogs currently available. This article describes a study carried out using instrumental bulletins and historical seismograms stored in the Sismos project database to study in greater detail the seismicity of the area and provide any information on other earthquakes that occurred in that sector of the Ligurian Apennines. Based on the results obtained, we propose that the earthquake of September 21, 1924, originally located offshore about two kilometers from the Ligurian coast, actually took place in the vicinity of Bargagli. Although this new position has no particular implications for the seismic hazard of the area, however, it represents an important information to be taken into account in the calculation of the return period and in the seismotectonic interpretation of the area.