A Legacy of Submarine Slope Failure in Seismic Reflection Data Along the Active Hikurangi Margin, Aotearoa New Zealand

Abstract Documenting and characterizing past submarine landslides is fundamental to understanding their distribution and frequency through time, and critical to assessing the associated hazard. The widespread availability of marine geophysical data at the active Hikurangi subduction margin, east of Aotearoa New Zealand, provides an excellent basis to map regional trends in landslide occurrence. We present a database that documents mass transport deposits (MTDs) in 30 marine geophysical surveys, encompassing ∼45,400 line‐km of 2D seismic profiles. We map and characterize 737 MTDs, showing variations in size, location and style of failure, which we attribute to changes in geomorphic setting from north to south. Mass transport deposits in the northern Hikurangi margin, characterized by a high taper wedge and seamount subduction, show a broad range in size, with the highest proportion of MTDs displaying blocky or intact internal architecture. The central margin, characterized by lower wedge taper, hosts the most MTDs (51%), albeit with the thinnest (on average) and clustering within interridge basins. The southern Hikurangi margin hosts widespread submarine canyons and the largest (on average) MTDs, based on area and thickness. We demonstrate the importance of seismic archives in providing new insights into MTD preservation and discuss the bias between seafloor geomorphology and subseafloor seismic data in quantifying MTD occurrence. Our findings support the interrogation of the varied and complex causes of submarine landslides along active margins generally, as well as regions prone to cascading geohazards and landslide‐induced tsunami.