Holocene scarp on the Sawtooth fault, central Idaho, USA, documented through lidar topographic analysis

Abstract

High-resolution lidar data reveal a prominent latest Pleistocene–Holocene scarp on the Sawtooth fault (central Idaho, United States). The fault scarp marks 55–65 km of the range front, and may comprise two segments. The scarp is 4–9 m high in latest Pleistocene glacial landforms (11–14 ka) and 2–3 m high in Holocene alluvial landforms, implying 2–3 postglacial rupture events. Patterns of fault scarp continuity, coupled with existing gravity data, suggest that active faulting may have migrated northward during Pleistocene time. Detailed comparisons of raw lidar digital elevation models (DEMs), bare-earth lidar DEMs, and field surveys indicate that the bare-earth lidar data document the fault scarp morphology accurately and allow for detailed fault analysis where field evaluation is difficult. The documentation of Holocene motion on the Sawtooth fault demonstrates that ENE-directed extension extends across central Idaho, and that the fault contributes to seismic hazards.