123-5 Mapping Active Faults in Oregon with New Lidar Data

Session: Quaternary Research to Characterize Environmental and Geological Hazards

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Abstract:

The geometry and late Quaternary slip history of active faults are key observables for understanding seismic hazard, crustal structure, regional tectonic processes, and geothermal resource potential. Baseline lidar data covering much of Eastern Oregon have been released over the past year, bringing statewide lidar coverage to ~92% and enabling systematic mapping of Quaternary faults in the Cascadia backarc region. Based on the current understanding of regional tectonics, these active faults accommodate normal faulting and oblique extension in the Cascade Arc and Basin and Range provinces, and varying extension, translation, and contraction in areas of northeastern Oregon related to block rotation and fault orientations.  The high-resolution (≥ 8 points/square meter) bare-earth lidar data allow for more accurate and detailed mapping  of active faults across Oregon than past approaches. In addition to improving spatial accuracy, the updated mapping will resolve discrepancies across state boundaries present in the current active fault database. The three-dimensional nature of the lidar data permit investigation of fault dip, scarp morphology, and separation of planar and linear markers. We are developing a semi-automated workflow for interrogating fault scarp morphology and vertical separation to apply to the thousands of active fault traces in the Oregon landscape. The collection of fault traces and vertical separation measurements will enable systematic study of displacement-length scaling across the region. Data from this analysis will inform our understanding of fault system connectivity as well as potential differences between purely tectonic faults and those associated with active magmatic systems. Currently we are in the initial stages of developing a lidar-based update to active fault traces in Oregon. Once mature, the fault inventory will enable a better understanding of ongoing deformation processes affecting the volcanic arc, forearc, and backarc of Cascadia, as well as the Columbia Plateau, Basin and Range, and Blue Mountains geologic provinces. These updated Quaternary deformation data will contribute to an improved characterization of seismic hazard across the region.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7390

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