Sampling the intermediate loop of the subduction factory at Nankai: The mud volcanoes of the Kumano Basin, Japan

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The major 2011 earthquake that devastated Japan has its origins in the subduction zone just west of the island in the Pacific Ocean. The presence of fluids on fault zones and trapped in rocks many times helps to lubricate slip or, when under stress, cause overpressuring and fracturing of the crust, resulting in fault motion and earthquakes. Knowing the origin of fluids in accretionary wedges that form just shoreward of subduction zones can help us better understand fault and earthquake dynamics. This research involves measuring the rate of fluid fluxes emanating from mud volcanoes in the area of a major international program that is studying the faulting and deformation associated with slip in the Nankai subduction zone (NanTroSEIZE). This funding allows a US scientist to participate in an international oceanographic cruise where his fluid meters will be deployed to collect a time-series set of fluid samples for later geochemical analysis in the laboratory. In addition cores will be taken to allow the study of sediments and associated pore waters. Samples from both devices will be analyzed for various key chemical elements and signatures that will illuminate the source of fluids and the chemical reactions going on in the mud volcanoes and sediments. The broader impacts of this project include increasing our knowledge of possible triggers of major earthquakes, support of an early career investigator, leveraging of ship time at no cost to NSF, international collaboration with German and Japanese scientists, and public outreach through a local aquarium. Public outreach activities include the interaction of scientists and aquarium staff and the development of learning materials for K-12 students. In terms of workforce training, a graduate student and undergraduates will be involved.