Presentation
Temporal patterns of slip rate on the Little Lake fault, eastern California shear zone, from terrestrial lidar, cosmogenic radionuclides, and InSAR analysis (Invited)
AGU Fall Meeting Abstracts
(2010)
Abstract
An ever-expanding inventory of fault slip-rates spanning various time intervals reveals contrasting spatial and temporal patterns of strain for active faults within the Eastern California shear zone (ECSZ). Comparison of data derived from geologic, geomorphic, and paleoseismic records with geodetic estimates of fault loading affords unparalleled opportunity to investigate the dynamics of earthquake processes and the evolution of an intracontinental plate boundary fault system. We focus here on the Little Lake fault, which lies along the western margin of the ECSZ between the Sierra Nevada and the Coso Range in east-central California. The fault accommodates between 10-20% of the total dextral motion within the ECSZ at this latitude and a smaller fraction of the relative motion between the Pacific and North American plates. Relatively high rates of decadal fault loading previously described for the Little Lake fault zone from GPS measurements and InSAR data suggest potential discrepancies with longer, late Quaternary records of fault slip. To address this inconsistency, we targeted a series of fluvial terraces related to overtopping and outflow from pluvial Owens Lake that cross the fault and record dextral offset since Late-Pleistocene time. High-resolution topographic surveying using a tripod-mounted laser scanner suggests between 33 and 38 m of reconstructed right-lateral displacement of two individual terrace risers over this time period. Coupled with cosmogenic 10Be dating of intact, meter-scale outwash boulders preserved on terrace treads bounding each riser, detailed characterization of these geomorphic features provides a robust geologic slip-rate estimate for the Little Lake fault zone at the ~104 year timescale. Preliminary correlation of terrace surfaces with available exposure dating of fluvially scoured basalt upstream at Fossil Falls suggests a right-lateral displacement-rate on the order of ~2 mm/yr. Although more than double the previously reported rate estimate (≤ 1 mm/yr) based on older, poorly constrained basalt flows, this result tentatively suggests that decadal rates (≥ ~5 mm/yr) on the Little Lake fault zone are not sustained over longer periods of time. New InSAR analysis of ERS-2 satellite images spanning 2001-2009 will enable a more precise comparison among geodetic strain and longer-term, late Quaternary records of geologic slip.
Keywords
- Cosmogenic-nuclide exposure dating,
- Tectonic deformation
Disciplines
- Geology and
- Geomorphology
Publication Date
December, 2010
Location
San Francisco, CA
Citation Information
Amos, C.B., R. Bürgmann, A.S. Jayko, G.B. Fisher III, and D.H. Rood (2010) Temporal patterns of slip rate on the Little Lake fault, eastern California shear zone, from terrestrial lidar, cosmogenic radionuclides, and InSAR analysis (Invited), Eos Trans. AGU, Fall Meet. Suppl., Abstract T44A-03.