New ocean bottom cabled seismic and tsunami observation system enhanced by ICT

Abstract

A new Ocean Bottom Cabled Seismic and Tsunami observation system (OBCST) has been developed for replacement of the existing cabled observation system off Sanriku, Japan, whose landing station was damaged by tsunamis of the 2011 Tohoku earthquake. Until 2010, we had already developed and installed the new compact Ocean Bottom Cabled Seismometer (OBCS) system near Awashima-island in the Japan Sea. After the installation, the OBCS system is being operated continuously and we have continuous seismic data for more than 3 years. The new OBCST system for off-Sanriku area is based on the Awashima system, and is characterized by system reliability using TCP/IP technology and down-sizing of an observation node using up-to-date electronics. The new OBCST system has new functions compared to the first system. An Ethernet of the system is upgraded to Giga-bit and clocks in observation nodes can be synchronized through TCP/IP protocol with an accuracy of 300 ns (IEEE 1588). In addition, power over Ethernet technology enables us to equip an external port for additional sensors. After installation of the cabled system, a scientific sensor can be added/replaced by using remotely operated vehicle. We have a plan to install the new OBCST system in 2015. The system has two observation nodes with three-component accelerometers and pressure gauge for tsunami observation and one node with accelerometers and an external port for additional sensors on seafloor. Total length of the practical system is approximately 100 km and an interval of the observation node is about 30 km. At the present, we are producing the observation nodes of the new OBCST. In this paper, we present a system of the new OBCST in detail, and installation plan.