Along-strike variation in subducting plate seismicity and mantle wedge attenuation related to fluid release beneath the North Island, New Zealand

At depths where the subducting slab interacts with the mantle wedge, along-arc variation in slab seismicity is a fundamental characteristic, with patches of abundant seismicity separated by low seismicity zones. The largest most numerous patch, at 150-220 km depth, underlies a pronounced low Qp zone in the mantle wedge, which is associated with the rhyolite-dominant Taupo caldera. Extensive melt in the region of low Qp requires high H2O flux from the underlying slab. The abundant Taupo seismicity suggests a correlation between melt production and regions of earthquake fracture permeability following embrittlement which promote migration of dehydration fluid. The hydration history of the incoming slab may be a key factor in producing variations in dehydration and intraslab fluid migration. Broader, extensive outer-rise yielding and hydration may have occurred near the approach of the re-entrant Hikurangi Plateau, forming the slab section that currently has high seismicity. Slab seismicity deepens from 240 to 330 km along-arc as the subduction rate increases from <20 to >40 mm/yr. The southwestern slab seismicity is bounded by an unusually narrow zone with 110-km depth extent. This is inferred to be a dehydration front related to heating at a slab edge that is located 70 km further southwest.