The PI's request funding to develop a portable platform to collect Global Positioning System - Acoustic (GPS-A) measurements to measuring seafloor deformation. The proposed system will be internally powered and autonomous, capable of collecting GPS-A data for a minimum of 24 hours while unattended. It will have two thrusters guided by GPS to automatically maintain its lateral position above an array of acoustic transponders on the sea floor. It will be portable, self-contained and deployable from a variety of vessels to open access to regions wherever there are ships-of-opportunity.
Broader Impacts:
After the Sumatra, Chile and Japan earthquakes the need for more knowledge and tools in this area/discipline is even more apparent. To further enable research in this area, new tools are required to engender new science. If successful, GEOSPAR will bring new knowledge on earth's active process both in research and education, as well as a view of disaster prevention against large earthquakes and resultant tsunami. Has direct impact upon science goals of four major NSF supported efforts: GeoPRISMS, the Cascadia Initiative, Earthscope, and the OOI cabled observatory (along the Cascadia Subduction Zone).
We have developed a new, lower cost approach to collect data for long-term measurements of seafloor deformation. Seafloor deformation is important to measure because it is the rapid displacement of the seafloor that causes tsunami, such as the one associated with the Great Japanese earthquake in 2011 and the 1964 Earthquake in Alaska. These regions are subduction zones where one tectonic plate slides beneath another at the rate of a few centimeters per year. Along the interface between these two plates there is friction and the motion of the downgoing plate slowing squeezes the upper plate. During the earthquake this built up displacement is released displacing the sea floor and causing the tsunami. With seafloor geodesy the slow squeezing of the plate can be measured and used to gage how much the sea floor could displace during the earthquake and thus the size of the tsunami. To measure the seafloor deformation we combine high-precision kinematic GPS positioning from an ocean surface platform with precision acoustic ranging from the platform to transponders on the seabed. The technique is called GPS-Acoustics (GPS-A) and was developed by our group here at the Scripps Institution of Oceanography. Wider adoption of GPS-A has been restricted by the high-cost of shiptime (~$50k/day). Our objective in this project was to find some platform other than a costly ship from which to collect the GPS-Acoustic data. Moored buoys are one option, but are costly to maintain. A more general solution uses a platform that extracts the kinetic energy of the ocean wave motion to derive propulsion and solar energy for running the payload, i.e., a Wave Glider from Liquid Robotics. We re-engineered the GPS-Acoustic hardware into a smaller and lower power form factor that fits into a Wave Glider. While ships cost thousands to tens-of-thousands of dollars per day to operate, the Wave Glider costs tens-of-dollars a day. We have successfully tested the Wave Glider GPS-A approach and used the system in Sept. 2014 in the Cascadia Subduction zone offshore Newport, Oregon. Present offshore studies of subduction zones such as Cascadia and Aleutians, have good geodetic coverage onshore and seismic surveys both on/off shore, but both subduction zones are lacking in offshore geodetic measurements. This new approach makes it cost effective to expand seafloor geodetic measurements in Cascadia and Aleutians.
