Tonga-Lau-Samoa Recovery cruise

An interdisciplinary project, consisting of seismic imaging, geochemical analysis of submarine lavas, and geodynamic modeling, is used to investigate the Tonga-Lau-Samoa system. Seismic observations will be obtained from an 18-month deployment of 30 Ocean Bottom Seismographs (OBSs) and 5 land seismometers (including 3 permanent stations) in the northern Tonga-Lau and Samoa regions. Several different seismic imaging techniques will provide 3-D velocity models of the upper mantle, precise earthquake locations will image the slab tear and associated deformation, and the variation of seismic velocity with direction will provide constraints on mantle flow. Lava samples will be dredged at 10 seamount locations east of the Tonga Trench to better understand subduction inputs into the northern Tonga Trench with the goal of understanding the distribution of enriched mantle material in the Lau Basin. The samples will be analyzed for isotopic compositions allowing identification of possible sources of non-Samoan hotspot materials in the Lau Basin, which is critical for geochemical interpretations of mantle flow. A series of geodynamic models will simulate slab-plume interactions with a variety of possible configurations. Using the integrated history of time-dependent mantle flow in the models, the predicted thermal structure and mantle textures can be directly compared with seismic and geochemical observations.