GEOCE (GEOphysical and OCEanographic observatory) measures tectonic seafloor motion from a mooring-based observing system which inherently lends itself to interdisciplinary research. The core system consists of a surface buoy with a highly accurate GPS sensor for both position and attitude of the buoy, and an acoustic transponder at the bottom of the buoy. Seafloor-mounted acoustic transponders are positioned around the buoy and accurately located from the ship after deployment. The combination of the GPS signals above the sea surface and subsurface acoustic ranging between buoy and bottom transducers allows buoy-based measurements of horizontal seafloor motion. Vertical seafloor motion is determined via high-precision bottom pressure measurements, after removing sea surface height motion (using the GPS) and internal ocean density fluctuations (using temperature and salinity data measured along the mooring line). The measurements of temperature and salinity by themselves have broad use in oceanography, and the surface platform with its power supplies and radio equipment is utilized to add meteorological sensors and current measurements, thus making this a comprehensive and interdisciplinary observing system.

More information is available on Michael Tryon's web page.

Measurement principles and system components of the GEOCE mooring.

Scientific party on the R/V Robert Gordon Sproul, August 14, 2008, before deployment of the first GEOCE buoy (visible in background) off Del Mar.

The surface buoy of the GEOCE mooring off Del Mar in fall 2008.