The goal of this research is to understand the cause of diffuse continental deformation in the western United States. This study will address the following problems: 1) The cause of Early Tertiary tectonic transition from crustal shortening to widespread extension in the North American Cordillera; 2) dynamic relationship between metamorphic core-complex formation to Basin and Range extension; 3) control of strain localization during the Basin and Range extension and initiation of the Eastern California Shear Zone; and 4) the relative roles of shear coupling across the plate boundary zone and gravitational collapse of the Basin and Range in controlling active crustal deformation in the western U.S. A sequence of quasi steady-state geodynamic models will be developed to explore the driving forces, lithospheric structures, and key tectonic boundary conditions that control continental deformation in the western U.S. at various critical stages of its Cenozoic evolution. These models will be fully three-dimensional with sufficient spatial resolution to incorporate important first-order variations of lithospheric structure including major fault zones. Viscoplastic rheology will be used for better simulation of strain localization in the crust. The models will be built using the finite element method with advanced algorithm and solvers, and the computer codes will be fully parallelized based on the Message Passing Interface standards to run efficiently on powerful PC clusters. Constrained by geologically derived kinematic boundary conditions of crustal deformation and plate boundary evolution, this suite of models will produce a 3D geodynamic reconstruction of Cenozoic tectonic evolution in the western U.S. through various critical stages in the last 40 million years.
This research will address the fundamental question of what causes and controls diffuse continental deformation. Plate tectonics theory predicts that tectonic processes, including crustal deformation and earthquakes, are concentrated along narrowly-defined plate boundaries. While this is generally true, broad diffuse deformation is found in many plate boundaries, especially in the continents. Crustal deformation extends thousands of kilometers from the plate boundary in western U.S. Understanding the dynamics of such diffuse deformation is important not only for geosciences but also for geohazards management, because widespread seismicity, volcanism, and landslides are associated with such deformation. Advanced computer models, such as the ones to be developed in this research, are needed to enable integration and interpretation of large volume multi-scale three-dimensional data sets generated by new observational technologies and multidisciplinary research initiatives
