The many double BSRs across the northern Hikurangi margin and their implications for subduction processes

The bottom simulating reflection (BSR) is widely observed along continental margins and believed to mark the base of gas hydrate stability zone (BGHSZ). In some regions, double or multiple overlapping BSRs are observed, yet their formation mechanisms geologic implications not well understood. Here we present 3D seismic images from 2018 NZ3D experiment that covers a 14×60km2 survey area on New Zealand's northern Hikurangi subduction margin. We observe in five locations. Beneath Tuaheni Basin mid-slope, secondary BSR (BSR2) lies ∼100-360 m deeper than primary (BSR1) its geometry mimics unconformity at basin. At three thrust ridges located 18-38 km deformation front, BSR2 ∼55-130 below sub-parallel BSR1. another ridge ∼14 forms above BSR1, two converge towards peak ridge. Through modeling BGHSZ analysis characteristics BSRs, identify potential for (1) rapid sedimentation, (2) tectonic uplift, (3) overpressure/heat advection caused by fluid migration. Our study demonstrates closely linked processes margin, may be used as indicators areas with recent and/or activities.