SGER: International Collaboration for Study of Deep Subduction Using Seismic Arrays in New Caledonia and Vanuatu

Miami University, Oxford OH

Investigators

Abstract

Subduction zones are a fundamental feature of the plate tectonic engine that drives the evolution of the Earth in addition to posing a great hazard, particularly in developing countries. One of the most poorly understood issues in subduction zones is the interaction between subducted lithosphere and the mantle transition zone (TZ). In particular, the amount of slab penetration across the 660-km discontinuity controls the rate of heat and mass transfer between the upper and lower mantle. This process is central to understanding thermal convection and chemical mixing of the mantle, including the continual search for a primordial mantle. The southwest Pacific presents a natural laboratory to examine the fate of subducted plates, as rapid subduction of old, cold lithosphere has been on-going to provide ample signal for understanding the slab-TZ interaction process. Moreover, abundant seismicity within the subducting lithosphere emits seismic waves that can illuminate properties and structure of the subduction zone. The only problem restricting studies in this region has been the lack of seismometers to record the frequent events, leaving researchers with limited means to directly sample the subducting slabs and examine the source of seismicity. It has recently come to light that Dr. Robert Pillet at the Institut de Recherche pour le Developpement (IRD) in Noumea, New Caledonia has been responsible for maintaining the Cavascope array of broad bandwidth (high-resolution) seismic instruments across New Caledonia and Vanuatu precisely where abundant seismicity can be used to probe the deep subduction zone. Pillet and the IRD-Noumea have agreed to release a portion of proprietary data from the entire Cavascope network for Brudzinski and Pillet to perform several in situ experiments to advance the understanding of how subducted lithosphere interacts with the bottom of the TZ and the origin of deep earthquakes. Broader Impacts include a partnership between a well-trained scientist in a developing nation with high-quality data but limited means for completing scientific projects, as well as a broader collaboration with other researchers in mineral physics, geodynamics, and seismology. Further impact will be sought through a unique field workshop at Miami University in which students receive realistic hands on educational experiences.