Structural Heterogeneity of the Alaska‐Aleutian Forearc: Implications for Interplate Coupling and Seismogenic Behaviors

Abstract We determine high‐resolution 3‐D seismic images ( Vp , Vs and / ) of the Alaska‐Aleutian forearc region, which are used to further estimate serpentinization volume fraction subducting Pacific slab. Our results show that hydration degree lower plate is high in Shumagin Gap but relatively low Semidi Kodiak segments, roughly shows a trend eastward decrease correlated with an increase interseismic slip deficit rate. The variation slab derived from our model uneven decreasing trend, well consistent along‐strike segmentation interplate coupling coseismic distributions 2020 Mw 7.8 Simeonof 2021 8.2 Chignik megathrust earthquakes. 7.6 Sand Point earthquake took place within strongly hydrated slab, whose occurrence was probably related rate affected by changes hydration. In addition, slow earthquakes occurred between pre‐subduction structures (e.g., bending faults, seamounts, fracture zones) fluid‐saturated overriding crust mantle wedge, where intraslab seismicity dehydration intensive. These features suggest lower‐plate may affect seismogenic behaviors subduction zones.