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Abstract Subduction zones are host to some of the largest and most devastating geohazards on Earth. The magnitude of these hazards is often measured by the amount of energy they release over short periods of time, which itself depends on how much stored energy is available for the geologic processes that drive these hazards. By considering the energy transfer among processes within subduction zones, we can identify the energy inputs and outputs to the system and estimate the stored energy. Due to the multiscale nature of subduction zone processes, developing an energy budget of subduction zone hazards requires integrating a wide range of geologic and geophysical field, laboratory, and modeling studies. We present a framework for developing mechanical energy budgets of upper crustal deformation that considers processes within the magmatic system, at the subduction zone interface, distributed and localized deformation between the arc and trench, and surface processes that erode, transport, and store sediments. The subduction energy budget framework provides a way to integrate data and model results to explore interactions between diverse processes. Because fault mechanics, sediment transport and magmatic processes within subduction zones do not act in isolation, we gain insights by considering the common energetic elements of the subduction zone system. Building energy budgets reveals gaps in our understanding of subduction zone processes, and thus highlights opportunities for new interdisciplinary research on subduction zone processes that can inform hazard potential. 

Uplift of the overriding plate at a subduction zone denotes interseismic strain accumulation, which is subsequently released during a megathrust earthquake. Although most interseismic strain is thought to be released elastically, observations of uplifted coastal regions at subduction zones worldwide indicate that some strain may result in permanent uplift. The Grays Harbor and Willapa Bay (Washington, USA) coastal region of the Cascadia subduction zone hosts flights of marine terraces testifying to late Pleistocene rock uplift. Our new detailed mapping of the marine terraces recognizes nine new units, including estuarine and fluvial sediments. Luminescence dating, relative age based on soil maturity and terrace elevation, and an evaluation of previous ages from fossil shells collectively constrain the probable ages of three estuarine units to sea-level high stands during Marine Isotope Stages 5a, 5c, and 5e. We estimate an average uplift rate of 0.4 ± 0.1 mm/yr for the terraced estuarine units, consistent with other Pleistocene uplift and incision rates in Cascadia. When compared with observed interseismic vertical deformation, these rates suggest that about one-tenth of interseismic strain may become permanent. The values are permissible within the uncertainties of uplift based on regional estimates of interseismic vertical strain rates and of coseismic subsidence.