HR: 0800h
AN: H31E-1348    [Abstracts]
TI: Beyond Finding Faults: Testing Tectonic Geomorphology Hypotheses with Airborne Laser Swath Mapping of the Eastern California Shear Zone
AU: * Oskin, M E
EM: oskin@unc.edu
AF: University of North Carolina at Chapel Hill, Department of Geological Sciences CB #3315, Chapel Hill, NC 27599 United States
AU: Strane, M
EM: strane@email.unc.edu
AF: University of North Carolina at Chapel Hill, Department of Geological Sciences CB #3315, Chapel Hill, NC 27599 United States
AU: Blumentritt, D
EM: blum0123@umn.edu
AF: University of Minnesota, Department of Geology and Geophysics, Minneapolis, MN 55455 United States
AU: Perg, L A
EM: lperg@umn.edu
AF: University of Minnesota, Department of Geology and Geophysics, Minneapolis, MN 55455 United States
AU: Gurney, E
EM: egurney@email.unc.edu
AF: University of North Carolina at Chapel Hill, Department of Geological Sciences CB #3315, Chapel Hill, NC 27599 United States
AB: High accuracy, densely sampled, and spatially extensive topographic data acquired via airborne laser swath mapping (ALSM) promises to revolutionize capabilities to quantify fault activity from tectonic geomorphology. Pioneering studies have highlighted the utility of ALSM to identify and measure Holocene fault ruptures beneath tree cover. In areas where multiple fault ruptures are preserved, substantial additional information on past fault activity may be extracted from the geomorphology and stratigraphy of unconformity-bounded (allostratigraphic) units deformed by fault slip. We describe results from 100 sq. km. of ALSM collected over active dextral faults of the Eastern California shear zone by the NSF Center for Airborne Laser Mapping. ALSM data were acquired to support mapping of Late Quaternary deposits and surfaces to quantify intermediate-term (10⁵ year) fault displacement and to inform cosmogenic dating strategy in order to best determine fault slip rates. We find that ALSM data are extremely valuable for differentiating allostratigraphic units remotely and in the field. Surface roughness and sharpness of eroded surface edges readily differentiate units of different ages. Subtle inset and onlap relationships between units, even of a few tens of centimeters or a fraction of a degree, are well defined. Though the locations of fault traces in the nearly vegetation-free desert terrain were known prior to the survey, several new fault strands have been identified cutting youthful alluvial fans and hilly terrain. For low slip-rate faults, ALSM aids in identifying and accurately measuring subtly warped channels and partially displaced alluvial fans. On high-slip rate faults where offset features are more apparent and measurement errors are commensurately lower, ALSM again proves its utility through testing whether intermediate offset positions are reasonable. Overall, ALSM increases the likelihood of successfully locating offset features and significantly enhances the quality of geomorphic mapping and measurement of fault slip.
DE: 1861 Sedimentation (4863)
DE: 8036 Paleoseismology (7221)
DE: 8040 Remote sensing
DE: 8094 Instruments and techniques
DE: 8175 Tectonics and landscape evolution
SC: Hydrology [H]
MN: Fall Meeting 2005