New compact ocean bottom cabled system for seismic observation in the Japan Sea

The Japanese islands are positioned near the plate convergent zones, and large earthquakes have repeatedly occurred in marine areas around Japan. Although there are already approximately 2,000 land-based earthquake observatories in Japan, the number of permanent earthquake observatories in the oceans is quite limited. It is important to observe seismic activities on the seafloor just above these seismogenic zones for understanding the generation of large earthquakes. An ocean bottom cabled seismometers system (OBCS) is the most suitable observation tool for this purpose since data can be obtained in real-time. We have developed a new compact OBCS system. The first installation of the new OBCS system will be done in the Sea of Japan in August in 2010. The OBCS system has a cable length of 25 km and four observation nodes with 5 km spacing. This paper describes the new compact OBCS system and the Sea of Japan OBCS project.