Thermal Structure of the Cascadia Subduction Zone on the Washington Margin

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To obtain an accurate estimate of conductive heat flux from the Cascadia accretionary prism, the PIs plan redundant methods to obtain both thermal and fluid flux measurements along a 2.5 D profile of the margin at a single latitude. In this profile they will use thermal blankets suitable for impenetrable sub-stratum, continuous fluid flow meters, multi-core deployments for sediment pore-water chemistry and thermal gradient measurements, and Jason-II heat flow probes. The heat flow and fluid flux data will be obtained at 10 specific equally-spaced depth intervals, along the margin from 2900 m to 500 m depths. The heat flow profile would also coincide spatially with other large-scale NSF programs planned for the Washington corridor at 47°N, including the OBSIP (Ocean Bottom Seismometer) focused deployment site, Endurance Array moorings for OOI, high resolution EM302 bathymetry surveys, and an Open Access 3-D MCS volume using the LANGSETH. The goal would be to obtain data of sufficient quality that downward projection of the surficial thermal gradients to the CSZ décollement and igneous basement can be made with reasonable confidence.The Open Data Access strategy developed by the MCS community is the new paradigm for geophysical data that has wide community interest, and we plan to follow that model. The planned heat flow, fluid flux and companion geophysical data will be made publically available (via GeoPRISM and UW web sites) in preliminary form, within 3 months of the end of the cruise. The project will also incorporate UW graduate and undergraduate students, as well as students from other institutions in the cruises and equipment development. The Grays Canyon area is within the treaty fishing zone of the Quinault Indian Nation, and the PIs plan to include students and teachers from the Tahola High School and Cascadia Community College in the field program.