[J07-3] Tracking the sea floor in motion III

[J07-3-01] New buoy platform system for crustal displacement observation

^○Narumi Takahashi^{1, 2}, Kentaro Imai², Yasuhisa Ishihara², Tatsuya Fukuda², Hiroshi Ochi², Misae Imano³, Yusaku Ohta³, Motoyuki Kido³, Shuichi Kodaira² (1.National Research Institute for Earth Science and Disaster Resilience, 2.Japan Agency for Marine Earth Science and Technology, 3.Tohoku University)

It is known that huge earthquakes occurred repeatedly around the Nankai Trough area and that coastal residents have received severe tsunami damages. The huge tsunami was brought by vertical displacement of the seafloor. Therefore, it is very important for local residents to receive the tsunami detection, to escape from tsunami and to evaluate crustal displacement. However, there are areas without the monitoring system like the dense oceanfloor network system for earthquakes and tsunamis (DONET). Therefore, we has developed a new buoy platform system for observation of tsunami and crustal displacement for five years. The large merit of the buoy platform is mobility and easy replacement. The system has a pressure gauge and acoustic transponders on the seafloor to observe crustal displacement and tsunami, and their signals are sent to our land station via the buoy using acoustic transmission and the iridium communication. Because it measures sea surface height using GNSS, the vertical crustal displacement can be also measured using the height and pressure gauge data. The buoy plays a role as the center of this system, which control timing to send acoustic signals, collect data from the seafloor and transfer the data to the land station. The buoy has to stand up to severe environment with sever typhoons and strong sea current with a speed of over 5 knots to realize long periods observation of the crustal displacement. To overcome above conditions and difficulties, we adopted some unique means for the system. Important technologies of this system are acoustic transmission between seafloor and the buoy, slack mooring to bear strong sea current, and the system stability. We introduce collected data and our remaining tasks currently for long observation under the severe conditions.