HR: 0800h
AN: H31E-1346    [Abstracts]
TI: Airborne Laser Swath Mapping as a Tool to Study Active Deformation Along the Death Valley Fault Zone, California
AU: * Frankel, K L
EM: kfrankel@usc.edu
AF: University of Southern California, Department of Earth Sciences 3651 Trousdale Parkway, Los Angeles, CA 90089 United States
AU: Dolan, J F
EM: dolan@usc.edu
AF: University of Southern California, Department of Earth Sciences 3651 Trousdale Parkway, Los Angeles, CA 90089 United States
AU: Finkel, R C
EM: rfinkel@llnl.gov
AF: Lawrence Livermore National Laboratory, Center for Accelerator Mass Spectrometry P.O. Box 808, L-206, Livermore, CA 94550 United States
AU: Wasklewicz, T
EM: twsklwcz@memphis.edu
AF: University of Memphis, Department of Earth Sciences 001 Johnson Hall, Memphis, TN 38152 United States
AB: The degree to which fault loading and strain release rates are constant in time and space is one of the most fundamental, unresolved issues in modern tectonics. In order to understand how strain is distributed across plate boundaries we must compare slip rate data over a wide range of time scales. The Death Valley fault zone (DVFZ) is one of the last major missing pieces of the kinematic puzzle in the eastern California shear zone (ECSZ). Published models of geodetic data suggest the DVFZ is storing much, and perhaps almost all, of the Pacific-North American plate boundary strain in the ECSZ north of the Garlock fault. However, the scarcity of geochronologically constrained long-term slip rates makes it difficult to determine whether strain storage and release have been constant along this part of the plate boundary. We are using airborne laser swath mapping (ALSM) data, together with cosmogenic nuclide geochronology and field mapping to determine geologic slip rates over a variety of time scales on this section of the plate boundary. The scarcity of vegetation in the study area is ideal for acquisition of ALSM data to survey deformed geomorphic features; removal of data points related to returns from the top of plants does not reduce the point density of bare-earth shots, as it might in a heavily-canopied area. We have acquired 46 km² of ALSM data from two locations along the northern DVFZ. In addition, approximately 100 km² of ALSM data have been collected along the central Death Valley normal fault. The ALSM data highlight many dextral and normal fault offsets in alluvial fans along the western piedmonts of the Black and Grapevine Mountains. These data are particularly useful for active tectonic studies because the landscape can be artificially illuminated from any azimuth and sun angle to reveal subtle topographic features that may not otherwise be seen. The amount of mid-Pleistocene to Holocene displacement on the fault system can be determined by restoring alluvial channel offsets observed in the ALSM data along the DVFZ to their pre-faulting positions. Minimum fault offsets in surfaces of varying age range from < 5 m in the youngest offset surface to 390 m in the oldest deformed surface. We have also used the ALSM data to construct surficial geologic maps of offset fans on the basis of slope maps and surface roughness characteristics. Field mapping using the ALSM data as a base map will augment digital analyses of the topography. Cosmogenic nuclide geochronology (¹⁰Be) will constrain the ages of deformed surfaces, and generate precise intermediate- and long-term slip rates from the restored fault offsets. Comparison of these longer-term rate data with short-term geodetic data will allow us to determine whether strain storage and release have been constant over the Holocene-late Pleistocene time scales of interest. Of particular importance is whether the potential strain transient observed in the Mojave section of the ECSZ extends north of the Garlock fault and away from the zone of structural complexity associated with the Big Bend of the San Andreas fault.
DE: 1150 Cosmogenic-nuclide exposure dating (4918)
DE: 1855 Remote sensing (1640)
DE: 8002 Continental neotectonics (8107)
DE: 8111 Continental tectonics: strike-slip and transform
SC: Hydrology [H]
MN: Fall Meeting 2005