Evaluating how well active fault mapping predicts earthquake surface-rupture locations

Earthquake surface-fault rupture location uncertainty is a key factor in fault displacement hazard analysis and informs risk mitigation strategies. Geologists often predict future locations from mapping based on the geomorphology interpreted remote-sensing data sets. However, surface processes can obscure location, traces may be mapped error, not break every trace. We assessed how well geomorphology-based predicted ruptures for seven earthquakes: 1983 M 6.9 Borah Peak, 2004 6.0 Parkfield, 2010 7.2 El Mayor–Cucapah, 2011 6.7 Fukushima-Hamadori, 2014 South Napa, 2016 7.8 Kaikoura, 7 Kumamoto. trained geoscience students to produce active maps using topography imagery acquired before earthquakes. A geologic professional completed “control” map. Mappers used new “geomorphic indicator ranking” approach rank confidence geomorphologic landforms. determined accuracy of faults by comparing published maps. defined as near (50–200 m, depending confidence) that interacted with landscape similar way fault. The between 12% 68% principal length studied median separation distances strong, distinct, or weak were 15–30 m. Our work highlights an underappreciated challenge analysis—even experts—with implications management, engineering site assessments, exclusion zones.