HR: 09:15h
AN: G51D-06    [Abstracts]
TI: InSAR Measurements of Interseismic Slip Rate and Deformation Patterns on the Southern San Andreas and San Jacinto Faults
AU: * Fialko, Y
EM: yfialko@ucsd.edu
AF: Yuri Fialko, IGPP-0225, Ja Lolla, CA 92093-0225 United States
AB: The southern section of the San Andreas fault (SAF), and portions of the San Jacinto fault (e.g., the Anza gap), have not produced significant (moment magnitude greater than 7) earthquakes in historic times, and therefore are currently believed to pose the largest seismic risk in California. Estimates of earthquake probability critically rely on the rate of interseismic strain accumulation. The point geodetic measurements and geologic data indicate that the southern SAF system accommodates a substantial fraction of the relative motion between the North American and Pacific plates, although the inferred slip rates vary greatly, from as low as 10 to as high as 35 mm/yr. I use a well-populated catalog of Synthetic Aperture Radar data acquired over southern California between 1992 and 2000 to generate a highly detailed map of interseismic deformation due to the southern San Andreas fault system. The deformation map reveals an asymmetric accumulation of strain on the southern San Andreas and San Jacinto faults, with the total horizontal velocity of 46 millimeters per year, consistent with the relative motion between the North American and Pacific plates. The asymmetry in the interseismic velocity field likely results from a material contrast across the faults, such that the Pacific side of the faults is more rigid than the North American side. Finite element modeling of interseismic deformation on the southern San Andreas fault system indicates that substantial (a factor of 3 or larger) changes in the static shear modulus across the faults are required to explain the data. The modeling results also suggest that the plate boundary deformation is nearly equally partitioned between the southern San Andreas and San Jacinto faults, with present-day slip rates of 25 and 21 millimeters per year, respectively. These slip rates are in excellent agreement with the long-term geologic data, suggesting that the fault slip rates are relatively constant over timescales up to 10⁶ years.
UR: http://sioviz.ucsd.edu/~fialko/research4.html
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 1236 Rheology of the lithosphere and mantle (7218, 8160)
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
SC: Geodesy [G]
MN: Fall Meeting 2005