Anisotropy Variations in the Alaska Subduction Zone Based on Shear‐Wave Splitting From Intraslab Earthquakes

Shear-wave splitting observations can provide insight into mantle flow, due to the link between deformation of rocks and their direction-dependent seismic wave velocities. We identify anisotropy in Cook Inlet segment Alaska subduction zone by analyzing parameters S waves from local intraslab earthquakes 50 200 km depths, recorded 2015–2017 emphasizing stations Southern Lithosphere Mantle Observation Network experiment. classify 678 high-quality shear-wave four regions, northwest southeast: (L1b) measurements parallel Pacific plate motion, (L1a) arc-perpendicular pattern, (L2) sharp transition arc-parallel splitting, (L3) motion. Forward modeling various fabrics shows that no one simple model fully explains observed patterns. An A-type olivine fabric with fast direction dipping 45° (300°)—aligned slab—predicts directions fit L1a well, but not L2. The inability forward all patterns suggests variations are variable ray angles, require distinct differences regime below arc, forearc, subducting plate.