Crustal Structure of the Hikurangi Margin From SHIRE Seismic Data and the Relationship Between Forearc Structure and Shallow Megathrust Slip Behavior

Abstract Marine multichannel and wide‐angle seismic data constrain crustal structure along a 530 km margin‐parallel transect of the Hikurangi subduction zone. The subducting Plateau crust ( V P 5.0–7.4 km/s) is ∼1 thicker (11 ± 1 km) mantle velocities are ∼0.2 km/s higher 8.3–8.5 beneath south/central relative to north Hikurangi. In overthrusting plate, an abrupt 0.5 south‐to‐north reduction in forearc wavespeeds occurs concert with change reflection character. We analyze legacy show that transition likely reflects lateral variability updip extent Torlesse Backstop. Furthermore, we map this unit along‐strike note broad correlation between backstop down‐dip shallow slow‐slip. propose geological architecture plate contributes spatial location frictional transitions margin, impacting both tsunami hazard.