HR: 17:00h
AN: T24B-05    [Abstracts]
TI: Refined images of the crust around the SAFOD drill site derived from combined active and passive seismic experiment data
AU: * Roecker, S
EM: roecks@rpi.edu
AF: RPI, 110 8th St., Troy, NY 12180 United States
AU: Thurber, C
EM: clifft@geology.wisc.edu
AF: UW-Madison, 1215 W. Dayton St., Madison, WI 53706 United States
AU: Shuler, A
EM: shulea@rpi.edu
AF: RPI, 110 8th St., Troy, NY 12180 United States
AU: Liu, Y
EM: yunfengl@geology.wisc.edu
AF: UW-Madison, 1215 W. Dayton St., Madison, WI 53706 United States
AU: Zhang, H
EM: hjzhang@geology.wisc.edu
AF: UW-Madison, 1215 W. Dayton St., Madison, WI 53706 United States
AU: Powell, L
EM: leep@geology.wisc.edu
AF: UW-Madison, 1215 W. Dayton St., Madison, WI 53706 United States
AB: Five years of effort collecting and analyzing earthquake and explosion data in the vicinity of the SAFOD drill site culminated in the determination of the final trajectory for summer 2005's Phase 2 drilling. The trajectory was defined to optimize the chance of reaching one of two adjacent M2 "target earthquake" fault patches, whose centroids are separated horizontally by about 50 meters, with one or more satellite coreholes planned for Phase 3 drilling in summer 2007. Some of the most critical data for the final targeting were explosion data recorded on a Paulsson Geophysical Services, Inc., 80-element 3-component borehole string and earthquake data recorded on a pair of 3-component Duke University geophones in the SAFOD borehole. We are now utilizing the full 5-year dataset to refine our knowledge of three-dimensional (3D) crustal structure, wave propagation characteristics, and earthquake locations around SAFOD. These efforts are proceeding in parallel in several directions. Improved picks from a careful reanalysis of shear waves observed on the PASO array will be used in deriving an improved tomographic 3D wavespeed model. We are using finite-difference waveform modeling to investigate waveform complexity for earthquakes in and near the target region, including fault-zone head waves and strong secondary S-wave arrivals. A variety of waveform imaging methods are being applied to image fine-scale 3D structure and subsurface scatterers, including fault zones. In the process, we aim to integrate geophysical logging and geologic observations with our models to try to associate the target region earthquake activity, which is occurring on two fault strands about 280 meters apart, with shear zones encountered in the SAFOD Phase-2 borehole. These observations will be agumented and the target earthquake locations further refined over the next 2 years through downhole and surface recording of natural earthquakes and surface shots conducted at PASO station locations.
DE: 7203 Body waves
DE: 7270 Tomography (6982, 8180)
DE: 8010 Fractures and faults
DE: 8150 Plate boundary: general (3040)
SC: Tectonophysics [T]
MN: Fall Meeting 2005