Geomorphological and geophysical analyses of the Hebron Fault, SW Namibia: implications for stable continental region seismic hazard

SUMMARY This study explores the geomorphological expression and geological context of a normal fault scarp in stable continental region (SCR) which we interpret as having failed large (Mw >7) earthquakes. Records such faulting events an SCR (or even more rapidly deforming regions) are extremely rare, so understanding this feature is international interest. The exceptionally well-preserved due to extensive calcrete/silcrete cementation. In areas where cementation reduced or absent diffuse, expected for formed by one paleoearthquakes. exceptional preservation aids comparison with data sets based on scarps have recently. Our analysis high-resolution digital elevation model Hebron Fault southern Namibia using pan-sharpened Worldview-3 satellite stereophotos (0.31 m resolution). We make height measurements at 160 locations providing improved estimates average displacement (5.9 m), maximum (10.1 minimum length (45 km). No consistent evidence lateral displacements water courses alluvial fan margins were found implying predominantly displacement. A newly described section northwest has en-echelon component strike-slip motion that may be explained its difference strike from central section. Most channels crossing show single knick-point. varies smoothly it crosses number different generations surfaces. multiscarp composite observed. therefore no mutiple-event origin scarp, although, lack does not conclusively demonstrate single-event origin. Published regressions, limited available SCRs, suggest mean ($\bar{D}_{\rm av}$) faults 1.2–3.1 likely 2–5 Mw = ∼7.1 though individual exceed these values. Comparison regional geology aeromagnetic suggests reactivates Mesoproterozoic ductile structure, Nam Shear Zone, location, orientation segmentation controlled alignment pre-existing structurally weak zones present-day stress regime. undergone repeated brittle reactivation, accumulating ∼110 vertical offset since deposition Ediacaran-to-Cambrian Nama Group. less than global compilations total data, suggesting attained current recruiting existing zone accumulate relatively constant future.