Differential Strain Accumulation Across Lake Tahoe as Measured From Submerged Paleo-shorelines

Abstract

The pattern of differential strain across two major fault strands within the Lake Tahoe basin has been mapped using a novel combination of high resolution seismic CHIRP, multibeam swath bathymetry, and airborne laser altimetry. Identification of submerged paleo-shorelines of late Pleistocene to early Holocene age allows this past excursion of lake-level to be used as a strain marker to evaluate the seismic hazard of the region. Tectonic disruption of this beveled surface (present depth, 11-26 meters) has resulted in 9-14 meters of discordance from east to west, and 6 to 7 meters of northward tilt along the eastern shore. The mechanism for lake draw-down, once thought to be prolonged drought, is revealed in seismic images that show a large outflow channel cross-cutting the lake's natural sill, suggesting catastrophic failure. Tectonic uplift and sub-aerial landslides within the Truckee canyon are likely mechanisms that stranded and in-filled this channel allowing Lake Tahoe to rise to modern levels. ROV observations confirm the origin of wave-cut paleo-shorelines, and show extensive moraine deposits to a depth of approximately 40ft, indicating active erosion within this interval during Tenaya/Tioga times.

Department

Center for Coastal and Ocean Mapping

Publication Date

12-2001

Volume

82, Issue 47

Journal Title

Fall Meeting, American Geophysical Union (AGU)

Conference Date

Dec 10 - Dec 14, 2001

Publisher Place

San Francisco, CA, USA

Publisher

American Geophysical Union Publications

Document Type

Conference Proceeding

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