Synthesis of the Seismic Structure of the Greater Alaska Region: Geodynamics Implications

EarthScope has fundamentally improved the characterization of the crust and mantle structure within and below the North American plate in Alaska and northwestern Canada. This study reviews the geodynamic implications of recent EarthScope seismic synthesis results in the context of recent and classic geodynamic models of both location-specific and generalized subduction, and the limitations of models therein. In particular, the study examines constraints geodynamic models place on the tectonic implications of the improved upper plate, slab, and mantle structure for slab dynamics, mantle flow, and upper plate deformation. First-order remaining questions are identified for the Aleutian–Alaska subduction zone, interior Alaska, and northwestern Canada, including how deeper slab structure may affect trench motion and upper plate deformation, mechanisms of flat slab subduction, and the role of the Yakutat plateau subduction-collision in these processes. EarthScope seismic syntheses for Alaska are considered in the larger context of the Pacific Ring of Fire multi-plate system, of which the Aleutian–Alaska subduction zone forms the northern boundary. Similarities and differences with other subduction zones along the Pacific Ring of Fire are examined, with the Aleutian–Alaska subduction zone serving as a window to tectonic processes elsewhere along the Pacific Ring of Fire.