This research is a collaboration between investigators at Washington University, Saint Louis, Missouri, and North Carolina State University, Raleigh, North Carolina. The funding will support a passive seismic experiment utilizing the PASSCAL portable seismic equipment, managed by the IRIS university consortium, in the Tonga, Fiji, and Vanuatu regions. Earthquakes occurring throughout the world will be recorded to study the structure of subducting slabs using phases converted at the upper slab interface, dispersion of phases traveling up the slab, and comparison of travel times between phases traveling inside and outside of the slab. The structure of the back arc basin will be studied utilizing regional earthquakes and SKS splitting from teleseisms. This study will improve information about the source processes of deep earthquakes in the most active deep seismic zone in the world, as well as provide better constraints on the tectonics of the deep slab, shallow trench and back-arc basin regions.
