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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.

We present the first broad-scale image of lithospheric thickness across the major tectonic domains of Alaska based on S wave receiver functions and joint interpretation with the potential field, seismic velocity, and heat flow measurements. Thus, we provide context for the distribution of strain throughout the Alaskan orocline. In the north, below the Brooks Range, a 130 km thick lithosphere is resolved, consistent with the presence of strong lithosphere that deflects strain to the south into central and southern Alaska. In southern Alaska beneath the Chugach and St. Elias Mountains, multiple interfaces are present, and we interpret a thinner (80-90 km) North American lithosphere above a deeper interface that represents the base of the Yakutat microplate, thereby extending it to the area below the Wrangell Volcanic Field and St. Elias Mountains. Immediately north of the E-W striking Denali Fault, shallow negative conversions (80 km) denote thin lithosphere in the greater back-arc region where heat flow is observed to be high. Thin lithosphere in eastern Alaska and adjacent Yukon Territory coincides with the occurrence of inboard crustal seismicity and may be indicative of transmitted compression caused by the collision of the Yakutat microplate. Relatively thin lithosphere (<90 km) south of the Arctic Alaska domain that is deforming throughout the Alaskan orocline may result from lithospheric thinning associated with guided deformation. Expansion of this model using the upcoming Transportable Array will be critical to establish lateral continuity (or lack thereof) of lithospheric structure and directly discriminate between existing regional deformation models