AOS :the adaptable observation system for real-time seafloor observation

Summary form only given. The submarine cable connected earthquake monitoring system is one tool for observation and had been deployed typical seismogenic zones around Japan since 1970s. Although, high efficiency seismic observation requires a high-density seismic measurement network, there is considerable technological difficulty in deploying as many sensors on the seafloor as on land. The existing observation network is still small scale and insufficient for an ideal observation network covering Japan. To solve this problem, JAMSTEK developed an expandable and replaceable satellite measurement station called the Adaptable Observation System (AOS) and designed the newest cable system to extend the existing cable observation using this system. The AOS is a battery operated mobile observatory connected to the backbone cable system by the thin fiber cable to ensure real-time data recovery. The system consists of a branching system, a junction box, a fiber cable, and a battery system for 6-month operation. The branching system is a part of backbone cable system and the other equipment make up the observation site. Installation and construction of the AOS will be conducted by a towed vehicle and an ROV. Submarine thin fiber cable is too delicate to install to the seafloor from the sea surface as same manners as backbone submarine cable. It is necessary to use some device to lay the cable right above the seafloor. The thin fiber scale laying system was designed to store more than 10 km of thin fiber cable in a cable bobbin and to maintain the tensile strength in the cable laying operation. Installation and construction of the AOS were conducted at the Off-Kushiro-Tokachi area by the underwater vehicles in JAMSTEC. The first trial system was successfully operated and confirmed the efficiency of mobile observatory in JAMSTEC. The first trials of this system were successfully operated and confirmed the efficiency of mobile observatory in the 6-month observation. We believe - his kind of system is a powerful too for future real-time seafloor observation and provides a chance to extend existing seafloor networks from in line to a wider area.