2005 Salt Lake City Annual Meeting (October 16–19, 2005)

Paper No. 13
Presentation Time: 11:15 AM


WHITE, Bonnie J.P.1, SMITH, R.B.1, PUSKAS, C.M.1, WONG, I.G.2 and SYLVESTER, A.G.3, (1)Department of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112, (2)URS Corporation, Seismic Hazards Group, Oakland, CA 94607, (3)Department of Geological Sciences, University of California, Santa Barbara, CA 93106, bpickering@mines.utah.edu

We have evaluated the earthquake, stress field, and contemporary deformation patterns of the Teton fault, WY, to examine the seismic cycle of normal faulting earthquakes. This large, high slip-rate normal fault raises important questions on the seismo-tectonics of intraplate faults that exhibit contemporary seismic quiescence. We developed a new 3D seismic velocity model and used it to produce a catalog of 8,000+ relocated earthquakes from a 17-year record from the Bureau of Reclamation Teton network. These data were used to examine and compare temporal and spatial variations in seismicity, stress field, and deformation. Teton seismicity is generally characterized by diffusely distributed epicenters, 0.5<M<4.7, with shallow focal depths less than 20 km and that occur on the east, west and south end of the Teton fault. Focal depths did not correlate with the down-dip projection of the Teton fault, suggesting homogeneous seismic moment release, but a gap of seismicity on the northern Teton fault is interesting given its high slip rate. Using the precisely relocated events, focal mechanisms were calculated for 463 high-quality events. Specifically, T-axes 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 and the southern Yellowstone volcanic field. Stress-field inversions using these data reveal a similar pattern in the minimum principal stress orientations but with unusual NS compression axes at the north end of the fault. The extension directions are generally consistent with directions inferred from a 15-station GPS network. They are also consistent with a rigid footwall but complexly deforming hangingwall revealed from 1st-order leveling line acquired over a 16-year monitoring period across the Teton fault. The stress field orientations derived in this study were also compared with fault stress-loading models of the Teton fault and their interaction with adjacent seismogenic structures such as the Hoback fault and several large right-stepping normal faults of the adjacent Yellowstone system. These data help refine the location and geometry of the Teton fault system and provide detailed seismic patterns, seismic rates, and possible stress-loading conditions as input into the probabilistic seismic hazard analysis.