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Holocene subaqueous paleoseismology of Lake Tahoe

Shane B. Smith, Robert E. Karlin, Graham M. Kent, Gordon G. Seitz and Neal W. Driscoll
Holocene subaqueous paleoseismology of Lake Tahoe
Geological Society of America Bulletin (January 2013) 125 (5-6): 691-708


Gravity-flow deposits recovered in a suite of sediment cores in Lake Tahoe were examined to determine if the event deposits were triggered by strong shaking from earthquakes on active faults within and in close proximity to the Lake Tahoe Basin. The acoustic character and distribution of individual lacustrine deposits as well as potential source regions were constrained by high-resolution seismic Chirp reflection and multibeam bathymetric data. Between 14 and 17 Holocene event deposits have been identified in Lake Tahoe, and examination of their source areas suggests they originated from different initiation points along the steep margin, with some being synchronous around the basin, as opposed to flood-related deposits. Lithologic characteristics, magnetic susceptibility, carbon and nitrogen isotopic signatures, opal content, and (super 14) C dating indicate that these event deposits are reworked lacustrine material. Radiocarbon dates indicate that the emplacement of these event deposit sediments correlates well with the late Holocene paleoseismic earthquake record developed for the Tahoe Basin. When taken alone, the causality of these events may appear ambiguous, but when the evidence is examined comprehensively, it suggests that strong shaking may likely have been the primary trigger for many of the event deposits observed in the lake throughout the Holocene. For example, four event deposits are assigned to Tahoe Basin faults. The most recent earthquakes occurred on the Incline Village fault (between 630 and 120 cal. yr B.P.); the southern segment of the West Tahoe fault (between 4510 and 4070 cal. yr B.P.); on the central and northern segments of the West Tahoe fault (5600-5330 cal. yr B.P.); and on the West Tahoe fault (between 7890 and 7190 cal. yr B.P.). The oldest of the four associated Tahoe Basin events coincides with the beginning of an extended period when Lake Tahoe was likely not spilling or spilling intermittently, and this suggests that active faulting and footwall uplift cut off the outlet at this time, exaggerating drought conditions downstream. Likewise, the event between 5600 and 5330 cal. yr B.P. on the West Tahoe fault may have exaggerated a smaller drought reflected downstream in Pyramid Lake. This event may also be the most recent event (MRE) on the largest segment of the West Tahoe fault. If correct, the period since the last rupture is approximately twice the estimated average recurrence interval for the Rubicon segment of the West Tahoe fault. A more complete Holocene record of strong shaking greatly extends the paleoseismic record in the region and indicates a combined recurrence interval of between 750 and 800 yr for all faults in the region.

ISSN: 0016-7606
EISSN: 1943-2674
Serial Title: Geological Society of America Bulletin
Serial Volume: 125
Serial Issue: 5-6
Title: Holocene subaqueous paleoseismology of Lake Tahoe
Affiliation: University of Nevada at Reno, Department of Geological Sciences, Reno, NV, United States
Pages: 691-708
Published: 20130111
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 63
Accession Number: 2013-016268
Categories: Quaternary geologyApplied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., 3 tables, geol. sketch maps
N38°55'60" - N39°13'60", W120°10'00" - W119°57'00"
Secondary Affiliation: California Geological Survey, USA, United StatesScripps Institution of Oceanography, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201311
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