Mapping and Understanding Seismic Anisotropy in the Northeast Pacific Ocean

This research provides an integrated analyses of seismic and other geophysical data that will elucidate the structure, heterogeneity, and dynamics of the ocean crust, lithosphere and asthenosphere in a 600~kilometer wide region west of the Moonless Mountain Seamounts on the Pacific plate halfway between the US mainland and Hawaii. Seismic data will be collected using an array of 25 ocean bottom seismometers. Research targets include a regional study, covering of the seismometer array deployment area which permits analysis of surface waves, receiver functions, surface wave azimuthal anisotropy, and shear-wave splitting in the area. Results provide insights into the local seismic structure of 40 to 50 million-year-old Pacific lithosphere and will answer questions about whether this area conforms to predictions from models of normal lithospheric plate cooling or if secondary processes, such as small-scale mantle convection, are impacting plate behavior and crustal/mantle structure. Results will be tested against predictions for a suite of mantle flow conditions and mineral alignment/anisotropy modes. The project will also use the newly collected surface wave data to improve global surface wave dispersion maps, reducing imaging biases in the global dataset that result, in part, from uneven data coverage in the study area. The ocean bottom seismometer array covers an area for which there is inadequate data for the Pacific Array as identified by the global community of seismologists. These data will serve a large global community of seismologists that conduct global tomographic and other studies that examine shallow and deep-Earth heterogeneity and processes that help us better understand how the Earth works and the impacts deep seated mantle-driven processes can have on Earth's surface. The work complements that recently carried out by an international, collaborative, group of US, UK, German, and French scientists in the Atlantic Ocean, which makes possible a comparison of results between both ocean basins.