NH43B-1878
GNSS Buoy Array in the Ocean for Natural Hazard Mitigation

Thursday, 17 December 2015
Poster Hall (Moscone South)
Teruyuki Kato1, Yukihiro Terada2, Shin-ichi Yamamoto3, Naohiko Iwakiri3, Morio Toyoshima3, Naokiyo Koshikawa4, Osamu Motohashi4, Gousei Hashimoto5 and Akira Wada6, (1)Earthquake Research Institute, University of Tokyo, Tokyo, Japan, (2)National Institute of Technology, Kochi College, Kochi, Japan, (3)National Institute of Information and Communications Technology - NICT, Tokyo, Japan, (4)Japan Aerospace Exploration Agency - JAXA, Tsukuba, Japan, (5)Space Engineering Development Co., Ltd., Tsukuba, Japan, (6)Hitachi Zosen Corporation, Tokyo, Japan
Abstract:
The GNSS buoy system for tsunami early warning has been developed in Japan. The system has been implemented as a national wave monitoring system and its record was used to update the tsunami warning at the 3.11 Tohoku-oki earthquake. The lessons learned in this experience was that the buoys are placed only less than 20km from the coast, which was not far enough for effective evacuation of people. We thus tried to improve the system for putting the buoy much farther from the coast. First, we tried to implement, different from current baseline mode RTK-GPS, a real-time PPP analysis strategy for positioning. In addition, we tried to use a two-way satellite data transmission in contrast with current surface radio system. We have made a series of experiments for this purpose in 2013 and 2014. A buoy of about 40km south of Shikoku, southwest Japan, was used for this purpose. GEONET data were used to obtain precise orbits and clocks of satellites. Then, the information was transferred to the GNSS buoy using LEX signal of QZSS satellite system. The received information on the buoy were used for real-time PPP analysis for every second. The obtained buoy position was then transmitted to the ground base, through an engineering test satellite, ETS-VIII. The received data was then disseminated to public through the internet. Both filtered short-term and long-term waves, were separately shown on the webpage.

The success of these experiments indicates that the GNSS buoy can be placed at least more than 1,500 km from the ground based tracking network. Given this success, we would now be able to deploy a new GNSS buoy array system in the wide ocean. An array in the ocean can be used for ionospheric and atmospheric research in the same region as well as tsunami or ocean bottom crustal deformation monitoring through an application to the GNSS-acoustic system. We are now designing a regional GNSS buoy array in the western Pacific as a synthetic natural hazard mitigation system.

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