HR: 0800h
AN: G21A-0126    [Abstracts]
TI: Estimation of tectonic stress rates from NeoKinema models in southern California
AU: * Liu, Z
EM: zliu@ess.ucla.edu
AF: University of California at Los Angeles, Department of Earth & Space Sciences 3806 Geology Building, Los Angeles, 90095 United States
AU: Bird, P
EM: pbird@ess.ucla.edu
AF: University of California at Los Angeles, Department of Earth & Space Sciences 3806 Geology Building, Los Angeles, 90095 United States
AU: Kagan, Y
EM: kagan@eq.ess.ucla.edu
AF: University of California at Los Angeles, Department of Earth & Space Sciences 3806 Geology Building, Los Angeles, 90095 United States
AU: Jackson, D
EM: djackson@ucla.edu
AF: University of California at Los Angeles, Department of Earth & Space Sciences 3806 Geology Building, Los Angeles, 90095 United States
AB: We applied 2-D kinematic F-E program NeoKinema to estimate long-term-average velocity, fault slip rates, and strain rate field in southern California. We use weighted least-squares to fit the input data (geological fault slip rates, geodetic benchmark velocities, and horizontal principal stress directions) and invert the velocity field. The grid is composed of mostly 7-km spherical-triangle finite element and 4-km fault bands. Geological fault slip rates, geodetic velocities, and stress directions are from California Geological Survey 2002, SCEC Community Motion Map3.0, and World Stress Map 2003, respectively. We have calculated $\sim$60 models to explore two tuning parameters to find the optimal model. Currently the best model has RMS discrepancies of $\sim$1.6 sigma for geodesy, $\sim$0.9 sigma for fault data, and $\sim$0.35 sigma for stress direction. The long-term-average velocity field is continuously/self-consistently corrected for temporary fault locking by summing the contributions of the faults that move freely at a constant rate below a locking depth with the slip rate determined in the optimized NeoKinema model. At present a constant locking depth is used for all faults and regular dislocation patches with constant dip angles are used in the correction. We do not consider the locking contributions from seismic slip in non-faulted elements as they are likely small. We computed strain rate from the "corrected" velocity field. The tectonic stressing rate is computed from strain rate assuming constant elastic modulus. Current results show that maximum tectonic shear stress accumulation concentrates around the major fast-moving faults such as San Andreas, San Jacinto etc. and that stress rate decays away from the faults. The newly derived tectonic stressing rate provides a better estimate of stress from plate tectonics since it utilizes the information from both geodetic and geologic data without preassuming any block dynamics. The comparison with tectonic stress rates estimated from rigid block models would expect to reveal new insights provided by this kinematic approach. The new estimation of tectonic stress accumulation, along with incremental stress release from each earthquake in the catalog, will allow us to test various earthquake interaction and triggering hypotheses.
DE: 8110 Continental tectonics--general (0905)
DE: 1206 Crustal movements--interplate (8155)
DE: 1208 Crustal movements--intraplate (8110)
DE: 1242 Seismic deformations (7205)
DE: 1243 Space geodetic surveys
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting