HR: 0800h
AN: T51D-1376    [Abstracts]
TI: Seismotectonics of the Teton Fault From a Revised Earthquake Catalog and Stress-Field Inversion
AU: * White, B P
EM: bpickering@mines.utah.edu
AF: Department of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112 United States
AU: Smith, R B
EM: R.Smith@earth.utah.edu
AF: Department of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112 United States
AU: Husen, S
EM: husen@sed.ethz.ch
AF: Swiss Sismological Service, ETH Hoenggerberg, Zurich, 8093 Switzerland
AU: Puskas, C M
EM: cmpuskas@mines.utah.edu
AF: Department of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112 United States
AU: Wong, I G
EM: Ivan_Wong@URSCorp.com
AF: URS Corporation, Seismic Hazards Group, Oakland, CA 94607 United States
AU: Sylvester, A G
EM: sylvester@geol.ucsb.edu
AF: Department of Geological Sciences, University of California, Santa Barbara, CA 93106 United States
AB: We have revised the 1986-2002 Bureau of Reclamation, Teton-Jackson Hole, WY, earthquake catalog using local earthquake tomographic inversion to determine a 3D velocity model for hypocenter relocations. The revised catalog data were then used to assess the seismogenic stress field, and to compare with the contemporary deformation pattern determined by geodetic measurements. This high slip-rate on the Teton fault raises important questions on the seismotectonics of intraplate faults that exhibit protracted periods of seismic quiescence and clustering. We developed a new 3D seismic velocity model to produce a catalog of 8,000+ relocated earthquakes for the Jackson Lake seismic network. A three-dimensional velocity model for precise hypocenter locations was computed by inverting P-wave arrivals from 2,069 high-quality events selected using a probabilistic selection criteria. The hypocenters were relocated using nonlinear probabilistic solutions. In addition, a new magnitude scale was determined using an improved coda magnitude equation. The new three-dimensional model combined with the hypocenter locations gives important structural information on the geometry of the Teton fault. Teton seismicity for the above period is generally characterized by diffusely distributed epicenters, 0.5 < M < 4.7, and focal depths no greater than 20 km. Seismicity occurs dominantly to the east, west, and south of the Teton fault, with a notable quiescence of earthquakes on the northern segment of the Teton fault. Preliminary results show that the hypocenters did not reveal a correlation with the hypothesized down-dip projection of the Teton fault, suggesting a more homogeneous seismic moment release in the surrounding upper crust. Using the preliminary 1D-velocity model relocated hypocenters, focal mechanisms were calculated for 463 high-quality events with gaps < 160, rms values < 0.5s, station to epicenter distance <1.5*focal depth, and at least 10 zero weighed P-observations. The seismically related stress field is characterized by generally horizontal T-axes that trend E-W in the vicinity of the Teton fault and surrounding areas, but rotate to a NE-SW trend around the northern tip of the Teton fault near the southern part of the Yellowstone volcanic field. Hanging-wall deformation directions are generally south to southwest relative to the footwall block as inferred from a 15-station GPS network occupied 1987-2003 and suggest a component fault-compression. These results are consistent with data from a1st-order leveling line acquired over a 16-year monitoring period, 1987-2003, across the Teton fault that suggests a rigid footwall but complexly deforming hanging-wall. The stress field orientations are also compared with elastic and visco-elastic fault stress-loading models of the Teton fault and their interaction with adjacent seismogenic structures. This new information helps refine the location and geometry of the Teton fault system, epicenter patterns, and possible stress-loading conditions as input for probabilistic seismic hazard analyses.
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8123 Dynamics: seismotectonics
SC: Tectonophysics [T]
MN: Fall Meeting 2005