A Design Study for an AUV Mounted Electromagnetic Surveying System

Rob Evans, Geology & Geophysics

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2014 DOEI Funded Project

Abstract

Many important processes of fluid exchange at the seafloor are poorly constrained because of a lack of techniques that can provide quantitative estimates of the volumes and temperatures of the fluids involved.  This includes low-temperature hydrothermal release at mid-ocean ridges; gas and brine discharge in areas of methane hydrate formation; and release at cold-seeps and pockmarks on the continental shelf and slope.  Furthermore, providing quantitative estimates of mineral volumes found in large hydrothermal deposits has also proven problematic.  The electrical conductivity of the seafloor is sensitive to a number of important physical properties including fluid content, temperature, and composition (particularly the presence of conductive metalliferous minerals).  Currently, there exists no technology capable of providing maps of the conductivity of the uppermost few tens of meters of seafloor over the kinds of rugged terrain common in areas of fluid discharge or mineralization.  We propose to carry out an initial engineering design for such a device that would make use of advances in AUV technology.  Our aim is to lay out the framework for a system that would use multiple AUVs, one carrying a transmitter generating a signal that is received remotely by devices mounted on one or more independent AUVs.  Our work will involve numerical modeling to determine an optimal system configuration and identification and bench-testing of sensor and other electronic components, chosen based on the modeling analysis that would be the framework for such a system and would provide sufficient background for a full development proposal.