Pilot Study Recommendations from the IRIS GSN Working Group on Long-Term Seafloor Seismographs

The purpose of the IRIS GSN Working Group on Long-Term Seafloor Seismographs is to gather information that will inform the deployment of long-term, high-quality, broadband seismic stations on the seafloor to complement existing permanent land stations. One of the working group's goals is to develop a concept of operations for a pilot station that includes identification of potential locations on the seafloor based on the science needs for imaging global earth structure and observing seismic sources. Findings from working group discussions in several community settings will be presented; these include a review of potential scientific targets, site occupation characteristics (deployment duration, data retrieval latency, sensor types), and plans for international collaboration. Responses to a related survey that was distributed to the global seismology community in March of 2018 provide further basis for a set of recommendations on how to move forward with pilot station planning. Consensus views from community feedback are that: i) the pilot station should use new technology (wave gliders, acoustic/optical telemetry means) relative to current temporary OBS deployments, ii) the focus should be on site occupation of 4+ years, iii) the deployment logistics and configuration should be repeatable at other locations, iv) the first site should fulfill the science/data needs but should also be within relatively easy reach of a U.S. port for easier site maintenance, v) data quality should be improved through burial and in-situ battery pack replacement without disturbing the sensor, and vi) the pilot project should provide results distinct and different from what can currently be accomplished with standard shorter-term deployments of OBS, either alone or in array configurations. This is complemented by an analysis of data types that are needed to provide the maximum amount of information for a variety of global seismology questions. The analysis suggests a location in the northern Atlantic Ocean as one of the optimal locations to maximize collection of seismic phases for receiver functions, mantle transition zone and upper mantle, lower mantle, Ultra Low Velocity Zones, and the outer and inner core structure.