All the People of Israel Are Friends: An Unknown Mid-Fifteenth Century Earthquake in the Marche Region (Central Italian Apennines) Recorded in a Coeval Hebrew Manuscript

Abstract Although the Italian seismic catalogs are considered among those with the best historical completeness, for periods prior to the Modern era they have gaps, often concentrated in limited regions. For example, Marche, a central Apennine region with high seismicity level, lacks any macroseismic observations throughout the entire fifteenth century. The chance discovery of a destructive earthquake summarized in a note written on a Hebrew prayer manuscript from 1446, not only helps us partially fill a gap in the seismic history of Italy but also prompts us to reflect on how much we still do not know about seismogenesis even in times covered by written sources.