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Preliminary Characterization of the Multorpor Mountain Fault: Evidence for Repeated Late Quaternary Faulting on the Mount Hood Fault Zone, North-central Oregon

The Mount Hood fault zone in north-central Oregon is a ~55 km-long, north-trending zone of active faulting along the western margin of the Hood River graben recently discovered from high-resolution LiDAR. The role that each fault section plays in accommodating Cascade intra-arc extension and regional crustal rotation remains poorly understood and their slip rate and recency of activity are not well constrained. One of the southwestern sections is the Multorpor Mountain fault, an east-dipping, 12 km-long normal fault. We used lidar to identify and map fault traces and extract topographic profiles across suspected fault scarps. We used MATLAB to measure and analyze 27 vertical offsets that range between 1 to 72 meters. The larger offsets cut through glacial deposits and Quaternary volcanic bedrock, while smaller offsets cut through most units such as Quaternary colluvial and alluvial slope deposits. These observations suggest that several surface-rupturing earthquakes have occurred on the Multorpor Mountain fault during late-Quaternary time. We ranked these displacements based on the quality and confidence of the correlative geomorphic surface that is offset across the fault. We then use empirical fault-scaling relationships for fault length, scarp height, and earthquake magnitude, and find that the Multorpor Mountain fault could rupture in ~M6.3 earthquakes. Our findings for the Multorpor Mountain fault section of the Mount Hood fault zone contribute to improved understanding of displacement along strike, fault characterization, and seismic hazard, offering new insight into how extensional strain is partitioned along active faults in the Cascade arc.

Session: The Landscape Record of Earthquakes and Faulting [Poster]

Type: Poster

Room: Exhibit Hall A+B

Date: 4/16/2026

Presentation Time: 08:00 AM (local time)

Presenting Author: Daisy Briseno

Student Presenter: Yes

Invited Presentation: 

Poster Number: 113

Additional Authors