Subduction Initiation

Subduction initiation may be the most enduring mystery in the study of terrestrial geodynamics. Most of our knowledge of the geodynamical processes involved in subduction initiation come from study of past initiation events where some evidence of the volcanic products have been preserved. The lack of ongoing examples of subduction initiation that include the classic sequence of forearc magmatism limits our understanding of how these processes occur. However, recent studies show that subduction initiation with accompanying magmatic activity is occurring along the Matthew and Hunter Trench between the New Hebrides Trench and the Fiji Platform. In this project we will we will deploy 20 passive broadband ocean bottom seismographs to investigate the structure and seismicity of the MHSZ. We will also conduct an extensive bathymetric survey and collect gravity and magnetic data to determine the tectonic setting and isostatic compensation of the region. This study will provide important observational constraints on processes associated with the initiation of slab underthrusting and the onset of overriding plate volcanism.