Integrated Ocean Drilling Program Expedition 328 scientific prospectus; Cascadia subduction zone ACORK observatory

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doi: 10.2204/iodp.sp.328.2010
Author(s): Davis, Earl; Petronotis, Katerina; Gamage, Kusali
Author Affiliation(s): Primary:
Geological Survey of Canada, Pacific Geoscience Centre, Sidney, BC, Canada
Integrated Ocean Drilling Program, United States
Source: Scientific Prospectus (Integrated Ocean Drilling Program), Vol.328, 33p. Publisher: IODP Management International, College Station, TX, United States. ISSN: 1932-9415
Note: In English. 18 refs.
Summary: Operations to be carried out during Integrated Ocean Drilling Program Expedition 328 will be devoted to the installation of a new permanent hydrologic observatory at Ocean Drilling Program (ODP) Site 889, the location originally chosen for a Circulation Obviation Retrofit Kit (CORK) installation during ODP Leg 146. During that attempt, rapid sediment intrusion into the perforations and bottom of an open-ended casing liner prevented proper sealing of the hole, and the objectives for the original CORK monitoring were never met. The format of the new installation will follow the Advanced CORK (ACORK) design, developed initially for installations at the Nankai subduction zone during ODP Leg 196. This configuration will facilitate pressure monitoring at multiple formation levels on the outside of a 10 3/4 inch casing string. The casing will be sealed at the bottom, leaving the inside available for future installation of additional monitoring instruments. Although drilling operations will be highly focused in a short period of time on site, a broad range of objectives will be addressed with monitoring over the decades to follow. These will include documenting the average state of pressure in the frontal part of the Cascadia accretionary prism, the pressure gradients driving flow from the consolidating sediments, the mode of formation of gas hydrates, the influence of hydrates and free gas on the mechanical properties of their host lithology, the response of the material to seismic ground motion, and the magnitude of strain at the site caused by episodic seismic and aseismic slip in this subduction setting. Initial instrumentation will include autonomously recorded seafloor and formation pressure sensors and seafloor temperature sensors. These, and other downhole instruments to measure temperature, tilt, and seismic ground motion to be deployed at a later date by submersible, will be connected to the NEPTUNE fiber-optic cable for power and real-time communications from land.
Year of Publication: 2010
Research Program: IODP Integrated Ocean Drilling Program
ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; 18 Geophysics, Solid-Earth; Accretionary wedges; Boreholes; Cascadia subduction zone; Downhole methods; Drilling; Earthquakes; East Pacific; Expedition 328; Gas hydrates; Geophysical methods; Geophysical profiles; Geophysical surveys; Integrated Ocean Drilling Program; Leg 146; Leg 168; Marine drilling; Marine sediments; Monitoring; North Pacific; Northeast Pacific; ODP Site 1027; ODP Site 889; Observatories; Ocean Drilling Program; Pacific Ocean; Planning; Plate tectonics; Pressure; Programs; Sediments; Seismic methods; Seismic profiles; Seismicity; Strain; Subduction zones; Surveys
Coordinates: N470000 N490000 W1260000 W1290000
Record ID: 2010037799
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