Exploring the Cascadia slab structure coupling 3D thermomechinal and CPO modeling.

The Cascadia Subduction Zone is characterized by young subducting lithosphere, its isolation from other subducting slabs, and its ability to produce megathrust earthquakes (M>9.0) and devastating tsunamis. Due to its high potential hazard and risk, it is also a well-studied subduction zone where modern, diverse and detailed observational datasets are available through the USGS and initiatives like GeoPrisms and EarthScope. These datasets include high quality GPS, onshore and offshore geophysical imaging, magmatic and seismic anisotropy data. These datasets present an opportunity to gain insight into slab structure, tectonic evolution, and present-day seismic hazards. Still, many questions remain about the physical processes that can self-consistently explain all the observations, and better estimate seismic hazards. For example, for the slab, geologic and geophysical data suggest that there may be one or two prominent slab gaps or tears, while tomographic data does not fully constrain the depth extent of the slab. Furthermore, the overriding plate is composed of several different terranes and contain numerous active and slowly moving faults, complicating efforts to accurately constrain variations in the overriding plate present-day stress and deformation rates.

In this study we test whether comparison of observations to model predictions can distinguish between different slab geometries for the Cascadia Subduction Zone. To this end, we have created regional 3D geodynamic models of Cascadia including the Cascadia slab based on the Slab 2.0 dataset. The model setup is built with the Geodynamic World Builder and, and the models are run using the mantle convection and lithospheric dynamics code ASPECT. During the evolution of these models we track the development of the CPO (Crystal Preferred Orientation), so we can compare it against seismic anisotropy data of the region. Our presentation will focus on the preliminary results of these models and demonstrate workflows for linking the model results to surface tectonics.