HR: 16:30h
AN: S34C-03 INVITED    [Abstracts]
TI: Imaging Rupture Asperities and Earthquake Potential of Partly Creeping Faults
AU: * Bürgmann, R
EM: burgmann@seismo.berkeley.edu
AF: University of California, Berkeley, 307 McCone Hall, Berkeley, CA 94720-4767, United States
AU: Funning, G
EM: gareth@ucr.edu
AF: University of California, Riverside, Department of Earth Sciences, Riverside, CA 92521, United States
AU: Johanson, I
EM: ijohanson@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025, United States
AU: Johnson, K
EM: kajjohns@indiana.edu
AF: Indiana University, 1001 East 10th Street, Bloomington, IN 47405, United States
AU: Nadeau, R
EM: nadeau@seismo.berkeley.edu
AF: University of California, Berkeley, 307 McCone Hall, Berkeley, CA 94720-4767, United States
AB: The Hayward fault (HF) and Parkfield segment of the San Andreas fault are known to be source areas of moderate to large earthquakes, but also exhibit significant aseismic fault creep. Modeling of space geodetic data (GPS, InSAR) collected along the HF over a ~10-year period allows for the determination of the distribution of currently locked asperities and creeping portions of the fault zone. Sequences of repeating micro-earthquakes add further resolution to the identification of creep at depth. The inferred slip rates along the creeping portions of the HF are significantly less than the long-term slip rate, and thus a substantial slip deficit is accumulating there as well. For purposes of earthquake hazard estimation, it is important to know how much of this slip deficit will be dynamically released during the next M~7 Hayward fault rupture, and how much will catch up during an episode of accelerated, but aseismic afterslip. The same question arises for other partly coupled faults, including many subduction thrusts. At Parkfield, geodetic and seismicity data also allowed for the first-order discrimination of creeping and locked fault patches, prior to the 2004 M=6 Parkfield earthquake. Model inversions of GPS and InSAR measurements spanning and in the immediate aftermath of the earthquake show that moment release by aseismic afterslip exceeded the coseismic moment, and that afterslip occurred on portions of the fault that experienced creep during the interseismic period. Thus, dynamic rupture does not appear to break deeply into previously creeping parts of the fault, which instead recover their slip deficit by accelerated creep. Mechanical models that treat fault creep in the context of rate-state-frictional behavior produce temporal and spatial patterns of fault slip consistent with these observations. Thus, the earthquake potential of partly creeping faults may be limited to rupture of completely locked asperities, whereas adjoining, creeping portions of the fault will accommodate slip by time-dependent, velocity-strengthening creep only.
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 1243 Space geodetic surveys
DE: 7209 Earthquake dynamics (1242)
DE: 8118 Dynamics and mechanics of faulting (8004)
SC: Seismology [S]
MN: 2007 Fall Meeting