North American Plate Dynamics and Western U.S. Deformation

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9903182 Humphreys The investigators will address North America plate dynamics by modeling the forces applied to the plate and comparing the predicted stresses with those inferred from the style of ongoing tectonics and those observed in drill holes. Modeling will be done with the finite element method. Input forces applied to modeled North America will include boundary and basal forces, and those generated internal to the plate (arising from potential energy variations such as those created by topography). The relative magnitudes of applied forces will be estimated to account for stress and deformation information. Furthermore, because the magnitude of many of the forces applied North America are well known a priori (such as ridge push), the magnitude of all the applied forces will be well constrained. Tectonic stresses deform North America at a rate inversely proportional to its strength. Strength will be modeled with a viscous rheology, which wil be estimated by ratioing the calculated stress with the (reasonably well-known) strain rate. This research can be divided into several tasks: 1) estimation of input fields, 2) description of an appropriate finite element representation of North America, 3) evaluation of model predictions against observables, and 4) as modeling progresses, toward resolving the input fields and assessment of their uniqueness.