Conductive heat flow variations from bottom‐simulating reflectors on the Hikurangi margin, New Zealand

Abstract

Bottom simulating reflectors (BSRs) represent the base of a gas hydrate zone underlain by widespread free gas. The extent of BSRs (>40,000 km2) has been mapped on the continental slope of the Hikurangi margin using industry and research seismic data. A conductive model was used to calculate heat flow from the depth of the BSR to the surface. A regional trend is observed, in which heat flow, uncorrected for sedimentation effects, decreases from an average of ∼50 mW m−2 at the toe of the accretionary prism to ∼35 mW m−2 at a distance 100 km landward from the deformation front. This trend reflects the processes of thickening accretionary wedge sediments and subduction of the Pacific plate and is in general agreement with heat flow values obtained using bottom‐hole temperature data. Local variations of heat flow were also observed, notably low and high values over the crest and flanks of anticlines. Numerical modeling indicates that much of this heat flow variation is due to a combination of variable seabed bathymetry and sedimentation effects. The dynamic effects of thrust faulting are found to be small and fluid flow along near‐surface faults is not predicted to contribute significantly to the observed heat flow anomalies along the modeled section.