Instrumented Borehole Seals for 1996 ODP Drilling on the Juan de Fuca Ridge

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9530426 Becker This project supports the fabrication of cable sensor systems and their deployment at six sites in the northeastern Pacific Ocean to study the hydrogeology of two regions of the Juan de Fuca Ridge. Dr. Keir Becker of University of Miami (Florida) will collaborate in the instrument development and integration with researchers from the Geologic Survey of Canada and engineers at Texas A&M University. The full sensor systems (supported herein) and data recording packages (built by GSC) will be installed in seafloor holes drilled by the drill ship JOIDES Resolution, operated by an international consortium led by the National Science Foundation. Borehole seal systems will be fabricated by engineers at Texas A&M University, the subcontractor responsible for JOIDES Resolution operations. The present study follows the successful development and deployment of these subseafloor "observatories," designated "CORKs," for hydrogeologic investigations in six previous holes in 1991-1994. It proposes refurbishment of two existing sites and deployment at four new sites to be drilled during summer 1996. The basic objective of the research is to define hydrogeologic properties of the seafloor in two different regions, addressing questions about rates of pore fluid flow within the ocean crust, and related questions about the degree of fracturing, bulk permeability and fracture heterogeneity, and the volume of mobile fluid in the rock "reservoir." This research is closely related to research on submarine hydrothermal systems and study of heat and chemical balances in the oceans, all of which must make implicit or explicit assumptions about these properties. The work undertaken in this project includes both passive monitoring of subsurface physical properties for multi-year duration and active pressure pulse transmission between existing drill holes to define intervening reservoir properties. Annual visits to the deployment sites and continuous data logging will provide unique long term record s of subcrustal processes. ***