Development of compact ocean bottom cabled seismometers system for spatially dense observation on sea floor and first installation plan

To install seismometers and tsunami-meters on the sea floor is necessary for monitoring seismic activities of a seismogenic zone. An ocean bottom cable seismometers system (OBCS) is most suitable for this purpose since data can be obtained in real-time. Some systems have been installed over the past 25 years around Japan. Although the existing OBCS systems are useful for the study of seismic activities, the number of station is limited due to their costs. Therefore lower cost in both production and installation by development of a portable system is expected. We have developed a new OBCS system. Utilization of the up-to-date ICT (Information and Communication Technologies) and semiconductor technologies is essential to reduce a size of the observation node and a cost of production and installation. We have a plan to install the new OBCS system in Japan Sea. The cable system has total length of 25 km and 4 observation nodes with 5 km interval. At the present, we are choosing an area for the deployment. The first installation of our new OBCS system is planed in 2010. This paper describes the new compact OBCS system in detail and presents a plan for the first installation.