Analysis of Negative Year Difference Cases in Natural Disaster Memorial Monuments

Japan’s Natural Disaster Memorial Monument Database (GSI) enables nationwide examination of how communities externalize disaster lessons in everyday places as cues that are perceptible, emotionally resonant, and repeatedly encountered. Using 2,098 monuments with both a construction year and a recorded target disaster year (of 2,377 entries; July 2025), we computed the year difference (construction year − recorded target disaster year). Most differences fall within 0-99 years (94.57%) and are concentrated within the first decade, indicating that many monuments are recorded as being constructed soon after disasters. Five monuments (0.24%) have negative year differences-constituting all negative-year cases in the analytic sample-an expectation-violating pattern in which the construction year predates the disaster year linked in the database and therefore requires interpretation. Document review of all five cases and fieldwork at two sites suggest two mechanisms: re-framing pre-existing monuments and representative-year selection within multi-event disaster histories. Negative year differences may thus reflect layered, updateable memory rather than simple errors. Treating such mismatches as analytic objects reframes monuments as dynamic material witnesses, highlights the role of visibility and repeated encounters in place-based risk-reduction education, and motivates metadata that can represent evolving narratives.