Dynamics and Kinematics of North America -Juan de Fuca- Pacific Plate Interaction: Constraints from GPS Geodesy and Geophysical Modeling

Central Washington University, Ellensburg WA

Investigators

Abstract

EAR-0003483 Miller Characterizing North American continental dynamics critically depends on constraining Pacific Northwest tectonics. The Pacific Northwest provides key constraints that differentiate dynamic models of active deformation in western North America at a plate boundary scale. The San Andreas system, entrainment of the Sierra Nevada block, and the role of modern Basin and Range extension in plate interaction and within-plate tectonics, cannot be accurately understood in ignorance of this region. Moreover, Cascadia is a global class natural laboratory for testing and comparing subduction zone interseismic strain accumulation models, models that are widely applied to other subduction zones where such testing is precluded by natural complexity. Unique paleoseismic constraints on a single, large-magnitude and relatively simple, margin-wide rupture of the 1700 A.D. subduction zone event make Cascadia an excellent case study of viscoelastic vs. elastic deformation models 300 years into the interseismic cycle. Rarely is such a simple system, of such vintage, so well known. The proposed continuation of geodetic and geophysical modeling studies will place first order constraints on crustal deformation in the Pacific Northwest, where they have direct implications for subduction zone mechanics and for continental dynamics, as well as for plate driving forces. These studies also directly support seismic risk evaluation in the urban corridor from Puget Sound to Portland, Oregon. The investigators will undertake completion of the PANGA velocity field and completion of dislocation modeling, as well as continued operation of the continuous PANGA GPS network. Meeting these goals requires ongoing observations by the PANGA array, setting these results results in the context of other western U.S. deformation arrays, continuing the regional kinematic and dynamic modeling studies, and refining recent models for subduction zone dynamics. This approach will resolve the superimposed interseismic (elastic and viscoelastic) subduction strain field from the regional secular stain field well enough to address the kinematic and dynamic models.