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Plattner, Christina (2009): Dynamic implications of Baja California microplate kinematics on the North America - Pacific plate boundary region. Dissertation, LMU München: Faculty of Geosciences
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Abstract

Many plate boundaries appear to be broad deformation zones, composed of several smaller microplates (e.g. California, Alaska, Mediterranean sea). To accurately address plate boundary deformation, as needed for seismic hazard assessment, it is important to study the motion of these microplates. Furthermore the dynamics of microplates, such as their driving forces and the implication of their motion on the surrounding plate boundary region are not well understood. Following suggestions from previous studies that Baja California is a microplate located within the North America – Pacific plate boundary region, a kinematic study using horizontal velocity data from Global Positioning System was performed. Building on the kinematic results and using numerical modelling techniques, a 2D mechanical model that simulates the transport of the Baja California microplate by lithospheric coupling with the Pacific plate was created. This model addresses the transport forces, and necessary preconditions in the North America – Pacific plate boundary region for rigid microplate transport. In addition, this model provides insights on the deformational response of western North America to Baja California motion, in particular the kinematic response of neighbouring microplates and the activation of passive fault systems. This latter was examined in more detail by separating the contribution of deformation from Baja California microplate motion and Sierra Nevada microplate motion to the formation of the Eastern California Shear Zone. Overall, it was found, that microplates play an important role for plate boundary kinematics and that their motion strongly influences the dynamics and fault evolution in plate boundary regions.