University of Miami - RSMAS
4600 Rickenbacker Causeway
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Geological Survey of Canada
Advanced CORK (ACORK) Data from the Nankai Trough,
Ocean Drilling Program Holes 808I and 1173B
Mikada, H., Becker, K., Moore, J.C., Klaus, A., et al., 2002. Proc. ODP, Init. Repts., 196: College Station, TX (Ocean Drilling Program). doi:10.2973/odp.proc.ir.196.2002
If you utilize the Nankai ACORK data from this site in any publications, please acknowledge support from the Ocean Drilling Program (ODP), Geological Survey of Canada, and the National Science Foundation (NSF grant OCE-0083156) for the original instrumentation as well as JAMSTEC for submersible support for the data downloads in 2002, 2003, 2004, and 2006-2008. (Note that the ACORK in Hole 1173B was visited and data downloaded only in 2002, 2004, 2006 and 2007.)
The ASCII datasets contain pressure values measured at 10-min intervals at the seafloor and several subseafloor depths in two "Advanced CORK" hydrologic observatories installed by ODP in 2001 at Sites 808I and 1173B in the Nankai Trough subduction zone.
The datasets were downloaded from logger memory using Japanese research submersibles at irregular intervals of 1-2 years. Currently there are 10 total datasets as follows: downloads at 808I in 2002, 2003, 2004, 2006, 2007, and 2008; downloads at 1173B in 2002, 2004, 2006, and 2007. They should be of interest to scientists studying seismogenic processes at subduction zones.
Please note that much of the data from 808I may be compromised by the lack of seal for the central bore. In addition, several of the valves on both installations were bumped open by a reentry camera frame during deployment, so the first year's installment of data from both sites was compromised until the valves were closed during the 2002 Kaiko operations.
There are separate data files for each of the downloads. Each data file has a header of basic metadata that describes the contents of the columns and the respective checks on logger clock drift. Typically, the clock drift was checked just before each download, and the clocks were then reset to UTC immediately after the respective downloads. In three cases, the records of the logger times checks have been misplaced and the drifts computed from other clock checks (consistent from year to year at each site, order 1-2 minutes per year) are reported. Note that the times in the data files have not been corrected for the clock drift. Also, during some of the download operations, there were attempts to calibrate the relative offsets among gauges by opening the seafloor valves to apply seafloor pressure to all the gauges. These are not reflected in the main data files.
Future ACORK data:
The installations have battery power for 10-15 years of operation, so there should be future downloads to add to the archive. The next opportunity appears to be on a JAMSTEC cruise in September 2009, and there are likely to be future opportunities at unpredictable intervals, hopefully 1-2 years. At ~5 Mb/yr, future datasets should be ~5-10 Mb in size.
Details of ACORK installations:
Deformation and Fluid Flow Processes in the Nankai Trough Accretionary Prism: Logging While Drilling and Advanced CORKs, in Proceedings of the Ocean Drilling Program, volume 196 Initial Reports Covering Leg 196 of the cruises of the Drilling Vessel JOIDES Resolution, Keelung, Taiwan, to Kochi, Japan, Sites 808 and 1173, 2 May - 1 July 2001.
(30 April 2002, ISSN 1096-2158, doi:10.2973/odp.proc.ir.196.2002).
Related Data at NGDC:
Related External Sites: