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New Paleoseismic Data Demonstrate Holocene Activity Along the Dog Valley Fault, Truckee, CA

Session: Cryptic Faults: Assessing Seismic Hazard on Slow Slipping, Blind or Distributed Fault Systems [Poster]

Type: Poster

Date: 4/21/2021

Presentation Time: 11:30 AM Pacific

Description: 

The Dog Valley fault is a left-lateral strike-slip fault in the Northern Walker Lane near Truckee, California and Reno, Nevada. Lidar data reveal youthful fault scarps along much of the ~25-km-long northeast striking fault, including in close proximity to the Stampede Reservoir dam. East of the Stampede dam, near Hoke Valley, CA, we excavated a series of 14 3-D paleoseismic trenches across an ~2 m high scarp. The trenches revealed a sequence of low energy fluvial deposits and buried meadow soils that were clearly displaced by a sequence of fault planes. A new methodology combining an iPad Pro lidar scanner with photo based structure-from-motion image reconstruction was developed to record and spatially reference each of the 14 trench slices. Using these referenced trench slices we were able to reconstruct an offset channel margin composed of interbedded thin carbon-rich peats and sand layers. The reconstruction shows that the channel intersects the fault at a high angle and is left-laterally displaced across the fault by ~80 cm with negligible vertical motion. The reconstructed fault geometry also reveals a right-stepping en-echelon fault pattern along strike. We observed clear evidence for at least one Holocene event. Here, the fault mapping, trench results, and radiocarbon ages demonstrate that this is a Holocene active fault that poses a significant seismic hazard to the Stampede Dam and surrounding communities.

Presenting Author: Ian K. D. Pierce

Student Presenter: No

Authors