HR: 08:50h
AN: V51F-04    [Abstracts]
TI: Effects of the Yellowstone Hotspot on Western U.S. Stress and Deformation
AU: * Puskas, C M
EM: c.puskas@utah.edu
AF: University of Utah, 135 S 1460 E, Salt Lake City, UT 84102, United States
AU: Smith, R B
EM: R.Smith@earth.utah.edu
AF: University of Utah, 135 S 1460 E, Salt Lake City, UT 84102, United States
AU: Flesch, L M
EM: lmflesch@purdue.edu
AF: Purdue University, 550 Stadium Mall Dr, West Lafayette, IN 47907, United States
AU: Settles, K
EM: ksettles@mines.utah.edu
AF: University of Utah, 135 S 1460 E, Salt Lake City, UT 84102, United States
AB: The Yellowstone hotspot is a major source of regional deformation and driving stress of a large part of the western U.S. The high elevation and accompanying geoid anomaly of the Yellowstone Plateau, site of current hotspot volcanism, is due to buoyancy forces from low-density upper mantle material. Low-density mantle underlies much of the Intermountain West and is attributed to lithospheric modification associated with Basin- Range extension and crustal thinning, as well as locally high deviatoric stresses from mantle buoyancy forces. Along the Yellowstone-Snake River Plain, magmatic activity has reworked the crust, most notably through crustal melting and intrusions that result in a partially molten silicic magma chamber beneath the Yellowstone Plateau and a corresponding solidified, dense, mid-crustal sill beneath the eastern Snake River Plain. The reworked crust of relatively lower density adds to the local gravitational potential energy (GPE), leading to some the highest stress gradients in the western U.S. interior. The regional deviatoric stresses are predominantly tensional, corresponding to ongoing extension at the Yellowstone Plateau and Basin-Range as observed by GPS measurements and L. Quaternary fault slip rates. Our stress models, constructed from the CRUST2.0 velocity model modified by seismic data and a YSRP gravity-density model, allow the quantification of the relative hotspot stress contributions from mass variations in the upper mantle and crust. This deviatoric stress solution is combined with deformation models from GPS and fault slip data to estimate a stress field boundary condition to quantify effects of relative plate motions. Dividing the magnitude of estimated deviatoric stress by the magnitude of strain rate allows for the calculation of the effective lithospheric viscosity, an indicator of crustal strength. We account for effects of large earthquake post-seismic viscoelastic deformation to assess whether they improve the correlation between long-term deviatoric stresses and modeled instantaneous strain rates. Both the stress and strain rate models are compared with tectonic provinces and seismicity to identify microplates within the western U.S. The results of these models confirm the profound effect of the Yellowstone hotspot on the regional deviatoric stress field, and the predicted high stresses can explain the observed high strain rates of the YSRP.
DE: 1209 Tectonic deformation (6924)
DE: 1211 Non-tectonic deformation
DE: 8137 Hotspots, large igneous provinces, and flood basalt volcanism
DE: 8164 Stresses: crust and lithosphere
DE: 8175 Tectonics and landscape evolution
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting