Reappraisal of the 22 October 1919 Central Italy Earthquake

This article reexamines the earthquake of 22 October 1919 using both macroseismic and instrumental data. The earthquake hit a desolate marshy area along the Latium coast, around 50 km southeast of Rome and was felt over a large area in central Italy. This event, known as the Anzio–Nettuno earthquake, has not been studied much, so the available literature sources are few and many uncertainties remain, especially in regards to its location, depth, and magnitude. The goal of the present work is to reappraise this earthquake by reinterpreting the known data and performing new historical research. Unpublished documents have been retrieved that contribute to a better description and allow us to produce a new macroseismic map. Epicentral coordinates have been recalculated and the magnitude estimated to be between Mw 4.5 and 4.8. After our revision, the earthquake appears smaller than in previous studies. A final consideration concerns the modified seismic risk in the area.