The Making of a Historical Earthquake: The Spurious A.D. 320, Alexandria (Egypt), Destructive Event

Abstract Alexandria in Egypt is reported to have been highly affected in A.D. 320 by an earthquake somewhat similar to the 1955 M 6.4 event, the strongest near-field event in this country since 1900. The A.D. 320 event was later characterized as spurious, reflecting a misunderstanding of a word referring to the impacts of the heresy of Arius on the Alexandria Church by the ninth century historian Theophanes. Shedding light on this earthquake is important because it is included in earthquake catalogs and studies of seismic risk; the latter is high due to the type of structures and foundation soils of Alexandria, a sprawling city of nearly six million people. An analysis of the previously examined and ignored ancient texts, of their sources, of their historical context, as well as of their copying, editorial, and translation history, indicates no earthquake in Alexandria in A.D. 320, nor that this spurious event reflects the misunderstanding of an ancient word. A possibility is that the information on an earthquake in the year A.D. 320, confirmed by another sixth century book, refers not to Alexandria, but to another town, the composite name of which was corrupted. According to this hypothesis, the A.D. 320 earthquake affected Alexandria Troas, on the Aegean coast, near the Homeric Troy, and close to a strand of the North Anatolian fault and the Aegean Sea, or Alexandria Catisson (Alexandria ad Issum), modern Iskenderun, near the East Anatolian fault. Both towns are in highly seismically active areas in Türkiye (Turkey).