HR: 1340h
AN: S23B-1388    [Abstracts]
TI: Development of a State-Wide 3-D Seismic Tomography Velocity Model for California
AU: * Thurber, C H
EM: thurber@geology.wisc.edu
AF: University of Wisconsin-Madison, Dept. of Geology & Geophysics, Madison, WI 53706, United States
AU: Lin, G
EM: glin@geology.wisc.edu
AF: University of Wisconsin-Madison, Dept. of Geology & Geophysics, Madison, WI 53706, United States
AU: Zhang, H
EM: hjzhang@mit.edu
AF: MIT, Dept. of Earth, Atmospheric, & Planetary Sci., Cambridge, MA 02138, United States
AU: Hauksson, E
EM: hauksson@gps.caltech.edu
AF: Caltech, Seismological Laboratory, Pasadena, CA 91125, United States
AU: Shearer, P
EM: pshearer@ucsd.edu
AF: UC San Diego, IGPP 0225, La Jolla, CA 92093, United States
AU: Waldhauser, F
EM: felixw@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964, United States
AU: Hardebeck, J
EM: jhardebeck@usgs.gov
AF: US Geological Survey, 345 Middlefield Rd, Menlo Park, CA 94025, United States
AU: Brocher, T
EM: brocher@usgs.gov
AF: US Geological Survey, 345 Middlefield Rd, Menlo Park, CA 94025, United States
AB: We report on progress towards the development of a state-wide tomographic model of the P-wave velocity for the crust and uppermost mantle of California. The dataset combines first arrival times from earthquakes and quarry blasts recorded on regional network stations and travel times of first arrivals from explosions and airguns recorded on profile receivers and network stations. The principal active-source datasets are Geysers-San Pablo Bay, Imperial Valley, Livermore, W. Mojave, Gilroy-Coyote Lake, Shasta region, Great Valley, Morro Bay, Mono Craters-Long Valley, PACE, S. Sierras, LARSE 1 and 2, Loma Prieta, BASIX, San Francisco Peninsula and Parkfield. Our beta-version model is coarse (uniform 30 km horizontal and variable vertical gridding) but is able to image the principal features in previous separate regional models for northern and southern California, such as the high-velocity subducting Gorda Plate, upper to middle crustal velocity highs beneath the Sierra Nevada and much of the Coast Ranges, the deep low-velocity basins of the Great Valley, Ventura, and Los Angeles, and a high- velocity body in the lower crust underlying the Great Valley. The new state-wide model has improved areal coverage compared to the previous models, and extends to greater depth due to the data at large epicentral distances. We plan a series of steps to improve the model. We are enlarging and calibrating the active-source dataset as we obtain additional picks from investigators and perform quality control analyses on the existing and new picks. We will also be adding data from more quarry blasts, mainly in northern California, following an identification and calibration procedure similar to Lin et al. (2006). Composite event construction (Lin et al., in press) will be carried out for northern California for use in conventional tomography. A major contribution of the state-wide model is the identification of earthquakes yielding arrival times at both the Northern California Seismic Network and the Southern California Seismic Network. These events are critical to the determination of the seismic velocity model in central California, in the former `no-mans-land' between the Northern and Southern California networks. Ultimately, a combination of active-source datasets, composite events, original catalog picks, and differential times from both waveform cross-correlation and catalog picks will be used in a double-difference tomography inversion.
DE: 7205 Continental crust (1219)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 7270 Tomography (6982, 8180)
SC: Seismology [S]
MN: 2007 Fall Meeting