a Multivariate Approach to Optimize Subseafloor Observatory Designs
Abstract
Long-term monitoring of the subseafloor has become a more common practice in the last few decades. Systems such as the Circulation Obviation Retrofit Kit (CORK) have been used since the 1970s to provide the scientific community with time series measurements of geophysical properties below the seafloor and in the latest versions with pore water sampling over time. The Simple Cabled Instrument for Measuring Parameters In-Situ (SCIMPI) is a new observatory instrument designed to study dynamic processes in the sub-seabed. SCIMPI makes time series measurements of temperature, pressure and electrical resistivity at a series of depths in the sub-seafloor, tailored for site-specific scientific objectives. SCIMPI's modular design enables this type of site-specific configuration, based on the study goals, combined with the sub-seafloor characteristics. The instrument is designed to take measurements in dynamic environments. After four years in development, SCIMPI is scheduled for first deployment on the Cascadia Margin within the NEPTUNE Canada observatory network. SCIMPI's flexible modular design simplifies the deployment and reduces the cost of measurements of physical properties. SCIMPI is expected to expand subseafloor observations into softer sediments and multiple depth intervals. In any observation system, the locations and number of sensors is a compromise between scientific objectives and cost. The subseafloor sensor positions within an observatory borehole have been determined in the past by identifying the major lithologies or major flux areas, based on individual analysis of the physical properties and logging measurements of the site. Here we present a multivariate approach for identifying the most significant depth intervals to instrument for long-term subseafloor observatories. Where borehole data are available (wireline logging, logging while drilling, physical properties and chemistry measurements), this approach will optimize the locations using an unbiased procedure that takes into account relationships among the data types that are not obvious when each value is analyzed independently. The low cost of the instrument provides the opportunity to use cables of different lengths and modules with varying capabilities to provide a flexible configuration. Determining the spatial distribution of modules based on the technique presented here will allow SCIMPI to be customized and deployed during the same expedition in which a site is drilled for first time.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMOS54A..05L
- Keywords:
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- 1694 GLOBAL CHANGE / Instruments and techniques;
- 4262 OCEANOGRAPHY: GENERAL / Ocean observing systems;
- 5194 PHYSICAL PROPERTIES OF ROCKS / Instruments and techniques