Exploiting Synergies between Academia and Industry to Mature Seabed Deformation Measurements.

Geraint West, Sonardyne International Ltd., Yateley, United Kingdom and C David Chadwell, University of California San Diego, La Jolla, CA, United States
Almost since the advent of GPS, scientists and engineers have taken for granted the ability to measure terrestrial mass movements to centimetric or better precision; however, until recently, equivalent measurements on the seabed were problematic. Nevertheless, the needs of both academia and industry to measure such movements on a centimetric scale have grown. In response to this, academia led development of the GPS-Acoustic (GPS-A) technique, while industry adapted Long BaseLine (LBL) techniques for this purpose.

First developed by Scripps Institution of Oceanography in the 1980s, GPS-A was developed as an approach to directly measure seabed tectonic movements, with the first site being established offshore Vancouver Island in the mid-1990s. Independently, Sonardyne International Ltd adapted LBL technology to monitor seabed deformation resulting from hydrocarbon extraction, with an operational system being deployed at Shell’s Ormen Lange field on the Norwegian Continental Shelf in 2007.
Although these approaches were quite different, they shared a number of challenges: The first of these being that the very slow velocities (typically a few centimetres per year) required instruments that can be left in situ for several years, while secondly, dependence on conventional ships to undertake measurements or recover data made operations prohibitively costly. In response to these challenges, both Scripps and Sonardyne developed long-life seabed transponders and Unmanned Surface Vehicle systems.

In 2012 the two came together as it became apparent that the technical developments were complementary and science requirements could be met with commercially supported instruments. As a consequence, Sonardyne instruments have now been deployed on Scripps’ GPS-A projects ranging from the Hikurangi Subduction Zone to the Aleutian Subduction Zone. The most recent project will see a large deployment of instruments as part of the North Cascadia Subduction Zone Observatory.