Mapped landslide deposits in Donner Lake, California, from high-resolution seismic data
Amber Warden – BS Candidate
Advisor: Dr. Jillian Maloney
December 10, 2021 at 9am
CSL 422
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Abstract
The Lake Tahoe Basin in the Sierra Nevada mountain range is tectonically active, with several major fault systems mapped across the region. Investigations in the southern basin identified synchronous landslide deposits in Fallen Leaf Lake, Cascade Lake, Emerald Bay, and Lake Tahoe, that were hypothesized to have been triggered by earthquakes on the basin-bounding West Tahoe-Dollar Point fault. Evidence for Holocene earthquakes in the northern Tahoe Basin is sparser, although several faults in addition to the West Tahoe-Dollar Point fault are mapped. High resolution Chirp data from Donner Lake, located northwest of Lake Tahoe, provide an opportunity to identify landslides that may have been triggered by events on these fault systems. Identification of earthquake triggered landslides can be used to define recurrence intervals, which are vital for seismic hazard assessments in the populated region. Here we present results from high-resolution seismic Chirp surveys of Donner Lake that image several potential slide deposits within the lake sediments, identifying five discrete slide deposits within lake sediments. Some slides are characterized by chaotic, hummocky character indicative of proximal deposits. Others are characterized by transparent layers that infill lows in topography, suggesting turbidity flows. While the occurrence of these slides may reflect strong earthquake shaking in the basin, a definitive triggering mechanism is still unknown. Future work to constrain the timing of the slides would show whether the Donner Lake slides are synchronous with slides in the southern basin. If so, this would suggest a major, basin-wide event. Future work is needed to investigate the timing and triggering of the newly identified slide deposits.