Advances in Seafloor Geodesy: Expanded Applications of Wave and Solar Powered Surface Vehicles

University Of California-San Diego Scripps Inst Of Oceanography, La Jolla CA

Investigators

Abstract

Subduction Zones are geologic faults that begin offshore where one tectonic plate slides beneath another. Due to friction along the fault some of the down-going plate motion is slowly transferred to the upper plate which bends and contracts storing the motion. Occasionally, this built-up motion is rapidly released as an earthquake and displaces the sea floor causing a tsunami. The Cascadia subduction zone offshore northern California, Oregon and Washington and the Aleutian subduction zone offshore Alaska have generated large earthquakes and tsunami in the past and will do so again. Measuring where and how fast this slow build-up occurs can improve understanding of the potential hazard. This requires offshore seafloor sensors to collect data, and in the past, ships to access this data. In this project, new methods will be develop and tested that use fewer instruments and remotely-piloted, self-powered sea surface vehicles, rather than ships, to lower the cost of data collection. This is a one-year project to implement acoustic upload of data from the sea floor to a wave- and solar-powered sea surface vehicle, and test a new lower cost method of collecting GPS-Acoustic data in shallow water (< 200 m) using a single seafloor transponder. An onboard computer will be programed to control the acoustic ranging system to operate in modem mode. A pressure sensor embedded with a transponder will be deployed offshore SIO to test the upload capability at varying ranges and depths. In addition, a transponder will be deployed offshore SIO and the sea surface vehicle will be operated remotely to circle the transponder for up to two weeks collecting GPS-Acoustic data. We will then evaluate if repeatability of positioning in shallow water is comparable to the existing GPS-Acoustic approach where data are collected from the center of an array comprised of three or more transponders.