The idea that the tectonics of Alaska and western Canada is defined by relatively discrete deformation along the boundary between the Pacific and North American plates has given way to a picture of broadly distributed deformation. While there are major fault systems, such as the Fairweather-Queen Charlotte transform and the Aleutian megathrust, where most of the deformation occurs along a single main structure, motion is often instead partitioned across multiple faults. Some regions appear to move as coherent rigid blocks while other regions are best described as zones of internal deformation. Strain is transferred far inboard as well as outboard of the main zones of deformation.
This new view of the northeastern Pacific is in part due to a number of studies and initiatives in recent years that have greatly expanded the density of GPS data throughout the region. Despite the advances, these studies have also lead to some problems when it comes to interpretation of the results. Each study used a different GPS dataset that spanned a different time epoch and used different processing techniques and parameters. Estimates of tectonic block and fault motion derived from the GPS data were developed using different modeling techniques, leading to incompatibilities that make it difficult to link and compare models. In addition, most of the studies were not able to utilize data from the Plate Boundary Observatory network of continuous GPS sites as the data time series from the sites were not yet mature. I will discuss efforts to develop an updated, unified GPS velocity field and an integrated tectonic block model for the region and highlight some of the new results that have come from this work.
By: Julie Elliott, Assistant Professor, Purdue University
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Host: Sean Gulick, UTIG