HR: 14:25h
AN: T23E-04    [Abstracts]
TI: P-wave and s-wave imaging from drill bit seismic data at SAFOD
AU: * Taylor, S T
EM: stewart.taylor@duke.edu
AF: Duke University, Box 90227, Durham, NC 27708 United States
AU: Miller, D
EM: dmiller@ridgefield.oilfield.slb.com
AF: Schlumberger-Doll Research, 36 Old Quarry Road, Ridgefield, CT 06877 United States
AU: Haldorsen, J B
EM: jhaldorsen@ridgefield.oilfield.slb.com
AF: Schlumberger-Doll Research, 36 Old Quarry Road, Ridgefield, CT 06877 United States
AU: Coates, R
EM: rcoates@ridgefield.oilfield.slb.com
AF: Schlumberger-Doll Research, 36 Old Quarry Road, Ridgefield, CT 06877 United States
AU: Malin, P
EM: malin@duke.edu
AF: Duke University, Box 90227, Durham, NC 27708 United States
AU: Shalev, E
EM: shalev@duke.edu
AF: Duke University, Box 90227, Durham, NC 27708 United States
AB: We have used the drill bit seismic technique to develop preliminary images of fracture and shear zones associated with the San Andreas Fault at the SAFOD site, Parkfield, California. Our study included the interpretation of the USGS PSINE surface seismic profile and the drill bit seismic data recorded by three different geophone arrays. Three-component geophones were used in two of the arrays, one of which consisted of a 1.2 km string of geophones in the SAFOD Pilot Hole. The multi-component data allowed us to use both p-wave and s-wave imaging techniques for delineating subsurface structure after updating the velocity models for the site. Our interpretation of the locations and dips of linear features imaged in the migrated drill bit seismic data correlates very well with locations and dips of faults in the PSINE profile. Using the available seismic datasets, we interpret numerous faults to cut the Cenozoic sedimentary cover, the Salinian block, and an apparent wedge of metasediments at the SAFOD site. Based on the structural pattern of downward converging faults and fracture zones, we interpret the fault system to comprise a flower structure that is directly related to the tectonic regime of the San Andreas Fault. The interpretation of a flower structure at SAFOD, which is located 1.8 km SW of the SAF, fits well with the surface geological mapping that has been conducted at the site. This mapping and our data indicates that a pervasive system of fractures and faults trend subparallel to the SAF in a zone up to 3 km SW of the main trace of the fault.
UR: http://www.icdp-online.de/sites/sanandreas/public/dbseis.html
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8010 Fractures and faults
DE: 8150 Plate boundary: general (3040)
DE: 8164 Stresses: crust and lithosphere
SC: Tectonophysics [T]
MN: Fall Meeting 2005