资源环境科技发展态势分析平台

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