HR: 0800h
AN: GP11A-0824    [Abstracts]
TI: Seismic and Magnetotelluric Interpretation Near Parkfield, California: Testing a Joint Inversion of Independent Data Sets.
AU: * Juli\`a, J
EM: jordi@duke.edu
AF: Duke University, Division of Earth and Ocean Sciences BOX 90227, Durham, NC 27705 United States
AU: Shalev, E
EM: shalev@duke.edu
AF: Duke University, Division of Earth and Ocean Sciences BOX 90227, Durham, NC 27705 United States
AU: Chavarr\'{\i}a, J
EM: jac4@duke.edu
AF: Duke University, Division of Earth and Ocean Sciences BOX 90227, Durham, NC 27705 United States
AU: Onacha, S
EM: onacha@duke.edu
AF: Duke University, Division of Earth and Ocean Sciences BOX 90227, Durham, NC 27705 United States
AU: Malin, P E
EM: malin@duke.edu
AF: Duke University, Division of Earth and Ocean Sciences BOX 90227, Durham, NC 27705 United States
AU: Hole, J
EM: hole@vt.edu
AF: Virginia Polytechnic Institute and State University, Department of Geological Science 1040 Derring Hall, Blacksburg, VA 24061 United States
AU: Ryberg, T
EM: trond@gfz-potsdam.de
AF: GeoForschungsZentrum Potsdam, Telegrafenberg E322, Potsdam, D-14473 Germany
AU: Cumming, W B
EM: wcumming@sonic.net
AF: Cumming Geoscience, 4728 Shade Tree Ln., Santa Rosa, CA 95405 United States
AU: Suemnicht, G
EM: gsuemnicht@sbcglobal.net
AF: Geologica, 703 Market St., San Francisco, CA 94102 United States
AB: We present a simultaneous interpretation of coincident magnetotelluric (MT) and seismic refraction lines near the Parkfield, CA, San Andreas Fault Observatory at Depth site. The MT data set was acquired with Phoenix 4-channel systems with average station spacing of about 250 m over a profile length of ($\sim$5000) m. The time-domain recording scheme was designed to yield data in the 0.01-200 Hz frequency band. The seismic travel-times were obtained from a SAFOD-related refraction/reflection line that was shot in the fall of 2003. The station and shot spacing for the line section coincident with the MT data were 50~m and 500~m, respectively. An initial, first-pass model of the seismic data suggests a simple structure lies beneath the study site: a 1.0-1.5 km thick, gradational, sedimentary layer with surface topography over a more uniform igneous basement. Modeling of the MT data alone shows a significant trade off exists in these data between the sediment thickness and the basement resistivity. To integrate the separate seismic and MT interpretations we combine both data sets into a joint inversion scheme by assuming that rapid velocity changes are accompanied with correspondingly rapid resistivity changes. We expect the combination will yield a mutually consistent estimate of sediment thickness and basement topography beneath the studied line.
DE: 7294 Instruments and techniques
DE: 3260 Inverse theory
DE: 1594 Instruments and techniques
DE: 0925 Magnetic and electrical methods
DE: 0935 Seismic methods (3025)
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting