HR: 0800h
AN: T21B-0597    [Abstracts]
TI: Timescale-dependent crustal deformation in the southwestern U.S.
AU: * Yang, Y
EM: yangyo@missouri.edu
AF: University of Missouri-Columbia, 101 Geology Bldg., Columbia, MO 65211, United States
AU: Liu, M
EM: lium@missouri.edu
AF: University of Missouri-Columbia, 101 Geology Bldg., Columbia, MO 65211, United States
AB: Space-based geodesy has greatly refined crustal deformation in the southwestern United States, but how the short-term strain rates relate to long-term deformation remains uncertain. The crustal kinematics based on GPS measurements differs significantly from that derived from geological reconstruction. We have developed a three- dimensional viscous finite element model to explore the driving forces for present-day crustal deformation in the southwestern US, and to reconcile its discrepancy with geological records for the past few million years. Our results show that plate boundary traction can reproduce the GPS velocity fields but not the observed stress field. Conversely, gravitational buoyancy force produces a good fit to the stress field but contributes little to the GPS velocity field. Models with both forces combined can explain the observed crustal deformation and stress patterns. The optimal plate boundary traction constrained from GPS data is too high to fit geologically determined crustal kinematics. We suggest that the plate boundary traction responsible for long-term crustal deformation should be lower than that constrained from GPS data, which represent mainly interseismic strain rates. By lowering the plate boundary traction, our model produces close fits to the observed long-term surface velocity and stress orientations. The fits may be further improved with a slightly weakened lithosphere, presumably associated with a stronger mantle thermal perturbation in the geological past.
UR: http://www.missouri.edu/~yangyo
DE: 8106 Continental margins: transform
DE: 8122 Dynamics: gravity and tectonics
DE: 8150 Plate boundary: general (3040)
DE: 8160 Rheology: general (1236, 8032)
DE: 8164 Stresses: crust and lithosphere
SC: Tectonophysics [T]
MN: 2007 Fall Meeting