HR: 14:55h
AN: G43A-05 [Abstracts]
TI: Estimation of a Time-Dependent Strain Rate Field in Southern California Using Continuous GPS Stations
in the SCIGN Network.
AU: * Hernandez, D
EM: danherna@ic.sunysb.edu
AF: Stony Brook University, Dept. of Geosciences, 255 Earth and Space Sciences Bldg., Stony Brook, NY
11794-2100
United States
AU: Holt, W E
EM: wholt@notes.cc.sunysb.edu
AF: Stony Brook University, Dept. of Geosciences, 255 Earth and Space Sciences Bldg., Stony Brook, NY
11794-2100
United States
AU: Bennett, R A
EM: rab@geo.arizona.edu
AF: University of Arizona, Dept. of Geosciences, Gould-Simpson Bldg. #77
1040 E. 4th St., Tucson, AZ 85721-0077
United States
AU: Li, C
EM: cuiping@geo.arizona.edu
AF: University of Arizona, Dept. of Geosciences, Gould-Simpson Bldg. #77
1040 E. 4th St., Tucson, AZ 85721-0077
United States
AU: Dimitrova, L L
EM: ldimitro@ic.sunysb.edu
AF: Stony Brook University, Dept. of Geosciences, 255 Earth and Space Sciences Bldg., Stony Brook, NY
11794-2100
United States
AU: Haines, A J
EM: haines@esc.cam.ac.uk
AF: Stony Brook University, Dept. of Geosciences, 255 Earth and Space Sciences Bldg., Stony Brook, NY
11794-2100
United States
AU: Haines, A J
EM: haines@esc.cam.ac.uk
AF: University of Cambridge, Dept. of Earth Sciences, Downing St., Cambridge, CB23EQ
United Kingdom
AB:
Advancements in the recognition of fine-scale deformation fluctuations have prompted a great deal of attention to be focused
on identifying and characterizing transient strain phenomena. We have developed a tool for recognizing strain rate transients
as well as for quantifying the magnitude and style of their temporal and spatial variations. Using time-varying velocity
estimates for continuous GPS station data from the Southern California Integrated GPS Network (SCIGN) for the time period
between October 1999 and February 2004 [Li et al., 2005]. We determine time-averaged velocity values in 0.05 year epochs for
each continuous velocity series. For each velocity field solution we determine a self-consistent model velocity gradient
tensor field solution for the region using bi-cubic Bessel interpolation of the GPS velocity vectors. For each epoch
solution we plot dilatation strain rates, shear strain rates, and the rotation rates. We also investigate the departures of
the model strain rate field and velocity field from a master solution, obtained from a time-averaged solution for the period
1999-2004, as well as estimating the departures of the time variable velocity gradient tensor field from other master
solutions, including models that incorporate plate motion constraints and Quaternary fault data. By combining the epoch
solution plots, we create movies that allow us to view the spatial and temporal changes in the dilation and shear strain rate
field in southern California. In the present solution several time-dependent changes are noteworthy. The Eastern
California Shear Zone (ECSZ) region, immediately following the October 1999 Hector Mine earthquake, shows a significant
spatial change of relatively high shear strain rate that increases from the immediate area of the earthquake to an area that
almost spans the entire ECSZ from east to west. Also following the Hector Mine event, there is a strain rate corridor that
extends through the Pinto Mt. fault connecting the ECSZ to the San Andreas Fault segment in the Salton Trough region. This
signal slowly decays while shear strain rates on segments of the San Andreas Fault, just east of Palm Springs, and the San
Jacinto increase during 2001-2004. During this period shear strain rates increase by roughly 20 nanostrain per year on the
San Andreas and 20-30 nanostrain per year on the San Jacinto (over a zone approximately 20 km wide). Moreover, seismicity
rates increase along these segments during this same time period in which shear strain rates increase. Results to date are
very promising in using this tool for investigating temporal variations in the deformation field. Our results quantify the
magnitudes of the strain rate changes and provide some bounds on their spatial coverage. Ultimately this tool should enable
us to separate out tectonic signals from other non-tectonic sources, such as hydrologic and atmospheric.
UR: http://rock.geo.sunysb.edu/~holt/EarthScope/
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 1209 Tectonic deformation (6924)
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
SC: Geodesy [G]
MN: Fall Meeting 2005