HR: 0800h
AN: T51D-1380    [Abstracts]
TI: New Paleoseismologic Observations From the Western Garlock Fault: Implications for Regional Fault Interactions
AU: * Madden, C L
EM: madden@earthconsultants.com
AF: Earth Consultants International, 150 El Camino Real, Tustin, CA 92867 United States
AU: Dolan, J F
T51D-1380 AF: University of Southern California, Department of Earth Sciences, University of Southern California , Los Angeles, CA 90089 United States
AU: Hartleb, R D
T51D-1380 AF: University of Southern California, Department of Earth Sciences, University of Southern California , Los Angeles, CA 90089 United States
AU: Gath, E M
T51D-1380 AF: Earth Consultants International, 150 El Camino Real, Tustin, CA 92867 United States
AB: New paleoseismic investigations on the western segment of the Garlock fault at Twin Lakes reveal evidence for three well-defined, and two additional, less-well-defined surface ruptures during about the past 5,600 years. Although two of these events had previously been identified at the site, their timing was not well constrained. Calibrated radiocarbon dates from detrital charcoal collected during our investigation broadly constrain the timing of the five events at Twin Lakes to about A.D. 1450-1640, A.D. 80-770 (possibly late during this range), 800-370 B.C., and 3670-2040 B.C (two events). A depositional hiatus between about 2000 and 800 B.C. could mask additional events. These data provide new insights into mid to late Holocene behavior of the Garlock fault. The timing of the most recent event on the western segment is correlative to the most recent event identified on the central segment at El Paso Peaks (A.D. 1450-1640), indicating that the two segments may rupture together during very large ruptures, or during smaller ruptures that occur within a relatively short period of time. More typically, however, the timing of events at the two sites is not correlative. For example only one event occurred at Twin Lakes (A.D. 80-620) during a cluster of three events at El Paso Peaks (A.D. 25-275, 250-475, 675-950). Conversely, one or more events ruptured the western segment (800-370 B.C., 3670-2040 B.C.) during a long hiatus (A.D. 25-2930 B.C.) on the central segment. This suggests different factors are responsible for strain loading and release for the two sections of the fault, including a westward decrease in slip rate of the western Garlock fault toward the intersection with the San Andreas fault, and the influence of nearby faults such as the San Andreas, or faults of the eastern California shear zone. Rupture from one segment to another may also be stopped by a 2-km-wide, extensional step-over between the segments at Koehn Lake.
DE: 8036 Paleoseismology (7221)
DE: 8100 TECTONOPHYSICS
SC: Tectonophysics [T]
MN: Fall Meeting 2005