Probing the subsurface of the Auckland Volcanic Field with ambient seismic noise

Current understanding of the Auckland Volcanic Field is predominantly based on geological and geochemical observations from the surface. Low local seismicity hinders passive seismic imaging efforts, whereas strong shallow heterogeneity reduces the resolution and penetration of active seismic models. To overcome these difficulties, we have estimated crustal shear-wave velocity profiles beneath the Auckland Volcanic Field from the ocean-generated ambient seismic noise. Variations in seismic velocity in the shallow crust correlate with variations in surface geology. In addition, our results highlight a contrast between oceanic and continental features in the Auckland Volcanic Field. Velocity models associated with the Waipapa Terrane (relative juvenile continental crust) tend to show a mid-crustal low-velocity anomaly, whereas a monotonic increase in velocity is associated with including the oceanic rocks in the ophiolite belt of the Dun Mountain-Maitai Terrane.