HR: 10:35h
AN: ED12A-02    [Abstracts]
TI: Movies of Finite Deformation within Western North American Plate Boundary Zone
AU: * Holt, W E
EM: wholt@mantle.geo.sunysb.edu
AF: Stony Brook University, Department of Geosciences, Stony Brook, NY 11794-2100 United States
AU: Birkes, B
EM: bbirkes@ashland.edu
AF: Ashland University, Department of Chemistry/Geology/Physics,401 College Avenue, Ashland, OH 44805 United States
AU: Richard, G A
EM: garichard@notes.cc.sunysb.edu
AF: Stony Brook University, Department of Geosciences, Stony Brook, NY 11794-2100 United States
AB: Animations of finite strain within deforming continental zones can be an important tool for both education and research. We present finite strain models for western North America. We have found that these moving images, which portray plate motions, landform uplift, and subsidence, are highly useful for enabling students to conceptualize the dramatic changes that can occur within plate boundary zones over geologic time. These models use instantaneous rates of strain inferred from both space geodetic observations and Quaternary fault slip rates. Geodetic velocities and Quaternary strain rates are interpolated to define a continuous, instantaneous velocity field for western North America. This velocity field is then used to track topography points and fault locations through time (both backward and forward in time), using small time steps, to produce a 6 million year image. The strain rate solution is updated at each time step, accounting for changes in boundary conditions of plate motion, and changes in fault orientation. Assuming zero volume change, Airy isostasy, and a ratio of erosion rate to tectonic uplift rate, the topography is also calculated as a function of time. The animations provide interesting moving images of the transform boundary, highlighting ongoing extension and subsidence, convergence and uplift, and large translations taking place within the strike-slip regime. Moving images of the strain components, uplift volume through time, and inferred erosion volume through time, have also been produced. These animations are an excellent demonstration for education purposes and also hold potential as an important tool for research enabling the quantification of finite rotations of fault blocks, potential erosion volume, uplift volume, and the influence of climate on these parameters. The models, however, point to numerous shortcomings of taking constraints from instantaneous calculations to provide insight into time evolution and reconstruction models. More rigorous calculations are needed to account for changes in dynamics (body forces) through time and resultant changes in fault behavior and crustal rheology.
DE: 8107 Continental neotectonics
DE: 8110 Continental tectonics--general (0905)
DE: 8115 Core processes (1507)
DE: 8158 Plate motions--present and recent (3040)
DE: 0845 Instructional tools
SC: Education and Human Resourcese [ED]
MN: 2004 AGU Fall Meeting