LIDAR EVALUATION OF BLUE RIDGE FAULT DISPLACEMENT ALONG STRIKE, IN THE MT. HOOD FAULT ZONE

Extension in the Cascade Range of the Pacific Northwest is accommodated by N-S trending faults on the Mount Hood Fault Zone. Vertical displacement on these faults offset Holocene and Last Glacial Maxima (LGM) surfaces and suggest relatively recent surface rupturing earthquakes, of large magnitude. The Blue Ridge Fault is an approximately 12 km long westward dipping fault located on the northern flank of Mt. Hood. It is an area of high topography with steep, heavily forested slopes. Recent LiDAR data allows us to identify and measure fault offset and uncertainty using GIS and DEM derivatives. In the summer of 2023, I reviewed earlier Blue Ridge Fault mapping in ArcGIS Pro, then measured vertical separation along strike. New surface exposure ages of a faulted LGM glacial moraine crest allows us to constrain a short-term slip rate and earthquake frequency. We combined offset glacial moraine measurements with our new 21.2 ka ± 3ka surface exposure age for this moraine and find an average slip rate of 0.13 ± 0.04 mm/yr. This slip accommodates ongoing extension at the crest of the Cascades. Empirical scaling relationships among scarp height, fault length, and magnitude allow us to determine that this fault could generate a maximum magnitude earthquake of Mw 6.2. Due to its proximity to critical infrastructure and nearby communities, understanding the potential hazards of this fault zone can inform future developments and emergency services.