Geology & Geophysics Meeting Report

At-Sea Workshop Advances Subduction Zone Research

International Ocean Discovery Program Core-Log-Seismic integration at Sea ([email protected]) workshop; Nankai Trough, Philippine Sea, off the coast of southwest Japan, January–February 2018

By , Gael Lymer, and Rina Fukuchi

Subduction plate boundaries are home to the world’s largest-magnitude earthquakes and can generate tsunamis with catastrophic effects on populated coastal regions, like what occurred in 2004 in Sumatra and 2011 in northeast Japan. Recent recognition of seismic slip, which can breach the seafloor, and documentation of shallow slow slip and tremor have motivated new deep-sea drilling investigations and real-time monitoring of the in situ physical and chemical properties of subduction zone deformation.

However, existing archives of core and borehole log data from previous ocean drilling expeditions also provide a repository of data available to address new research questions with state-of-the-art analytical techniques. The first International Ocean Discovery Program (IODP) Core-Log-Seismic integration at Sea ([email protected]) workshop was motivated by the dual need to leverage these legacy data for future research and to train the next generation of early-career scientists in ocean drilling science.

The [email protected] workshop focused on integrating IODP data from the southwest Japan Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) to address the role of the frontal prism in tsunamigenic earthquakes and slow slip in the shallow portion of the subduction interface. Over the past decade, the NanTroSEIZE project has involved 2-D and 3-D seismic surveys, coring and logging, installation of long-term borehole monitoring systems (LTBMS), and connection to the Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) across the Nankai accretionary prism. This combination has resulted in one of the best-imaged and -monitored subduction systems in the world.

A research vessel hosts an at-sea ocean drilling workshop focused on subduction zone earthquakes that generate tsunamis
Panorama from the helideck of the D/V Chikyu as it docks at Japan’s Shimizu Port. Credit: Christine Regalla

The [email protected] workshop was organized on board the D/V Chikyu concurrent with IODP Expedition 380, allowing workshop participants to interact with expedition scientists installing an LTBMS observatory at the site where the workshop’s research was focused. Well-preserved cores from across the prism toe were temporarily transported from the Kochi Core Center on board the Chikyu, where they were made available for new description, sampling, and analysis. Logging data, drilling parameters, and seismic data were also available for use by workshop participants, who were granted access to Chikyu laboratory facilities and software to perform analyses at sea.

A core aspect of [email protected] was to connect expert scientist mentors with early-career workshop participants from different backgrounds to work on common scientific questions. Multithematic presentations facilitated knowledge transfer between parties and field areas and highlighted the value of multidisciplinary collaboration that integrates processes across different spatiotemporal scales. Lively discussions in a cordial atmosphere and teamwork between mentors, participants, and IODP staff in a focused environment on board the Chikyu were key components of efficient development of individual and collaborative research and publication plans.

This workshop led to the synthesis of data and formulation of key outstanding research questions in a summary report submitted to Scientific Drilling. Workshop participants have also planned postcruise meetings to enable continued international collaboration. The productivity of this workshop demonstrated the research and educational value of organizing a [email protected] All scientific ocean drilling products are openly available for further scientific analyses, making similar workshops transportable to a variety of scientific disciplines and research focuses.

—Christine Regalla (email: [email protected]; @Rengellia), Department of Earth and Environment, Boston University, Mass.; Gael Lymer (@GaelLymer), Dynamic Earth Research Group, University of Birmingham, U.K.; and Rina Fukuchi (@fukuchi_rina), Research and Development Center for Earthquake and Tsunami, Japan Agency for Marine-Earth Science and Technology, Kanagawa; now at Department of Ocean Floor Geoscience, Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba, Japan

Citation: Regalla, C., G. Lymer, and R. Fukuchi (2018), At-sea workshop advances subduction zone research, Eos, 99, https://doi.org/10.1029/2018EO102669. Published on 30 July 2018.
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