High-Detail Fault Segmentation: Deep Insight into the Anatomy of the 1983 Borah Peak Earthquake Rupture Zone (Mw 6.9, Idaho, USA)

Abstract Following observations made in a survey campaign along the Lost River Fault (Idaho, USA) 2019, we integrate both original and previously published data to obtain detailed segmentation of fault sections that failed 1983 Borah Peak earthquake (Mw 6.9). The ruptured topographic surface with an oblique-normal faulting mechanism, activating two SW-dipping segments (Thousand Springs Warm Springs) branching SSW-dipping (Arentson Gulch Fault) producing coseismic ruptures up 3 m vertical separation. We augment description by interpreting high-resolution topography mapping. use quality separation data, rupture zone width measurements, slip analyze major minor structural-geometric complexities, highlighting partition deformation into four detail levels (i.e., segments, sections, subsections, sectors). Our work provides new details earthquake, constraints for paleoseismic seismotectonic studies, methodological approach applicable other areas world. fault-slip show variations fault-strike interpret as kinematic partitioning. In 1983, main southern segment had large width, while northern localized deformation. distributed accommodate portion length (~19.5 km versus 31 rupture) displacement (~66%). 83% 80% are located at hanging wall rupture. There is strong correlation between separation, position (footwall or wall), geometry. highlight control obliquity partitioning expression propagation. 1983) long-term Quaternary) behavior, showing activated similar cumulated behaviors distributing synthetic antithetic ruptures, despite different geometries. results have implications behavior application hazard.