Multiscale crustal architecture of Alaska inferred from P reciever functions

Abstract

The geologic mosaic of continental and oceanic terranes, displaced and deformed by multiple plate reorganization episodes, rapid lateral topographic variations, and heterogeneous distribution of strain throughout Alaska, all predict strong variability of crustal architecture. We present the first wide-scale model of crustal thickness based on broadband seismic data across the region that is constrained where seismic instrumentation has been deployed; dense coverage in the south-central region and more sparse coverage in the western and Arctic regions as the USArray Transportable Array (TA) is installed. Analyses of P receiver functions (PRFs) provide the first detailed look at crustal structure across all of Alaska. The variable thickness reflects inherited structure from Mesozoic to early Cenozoic convergent and extension events that in some regions is being extensively modified by ongoing convergence and collision, particularly along the active southern margin. Beneath the southern Alaska forearc to the central Alaska Range, the Yakutat slab Moho is also observed, illustrating the most recent ongoing accretionary event resulting from the collision of the Yakutat microplate. Combining three different receiver function methodologies, i.e., common conversion point stacking, receiver function stacks, and receiver gathers, for viewing and imaging P receiver functions allows for an interpretation of Alaskan crustal structure that spans multiple scales. The four-dimensional interpretation of the Alaskan crust will continue to evolve as the full TA is deployed and geologic studies are combined with the interpretations from this extensive seismic experiment.