Long-Term Continuous Seafloor Observation for Earthquake and Tsunami Using Developed ICT Cable Observation System off Sanriku, Japan

A development of Ocean Bottom Cabled Seismometer and Tsunami-meter (OBCST) system using Information and Communication Technology (ICT) started from 2012. The OBCST secures reliability by redundancy of commercial hardware and software, which provide with lower cost. The practical OBCST was deployed of F Sanriku in 2015, has three observation units and length of 105 km. Seismometers, a pressure gauge and a PoE external port can be equipped and the system implements ICT for data acquisition and communication. The OBCST system has been collecting data continuously from the installation for approximately 9 years since the deployment in 2015. From long-term data, we confirmed that ambient seismic and pressure noise levels have little variation for the whole operating period. An ambient seismic noise was comparable to that from a previous cable observation system. Pressure gauges provide data with a resolution of <1 hPa limited to environmental noise. Reflecting the low-noise environment, many local earthquakes, teleseismic events and tsunamis have been recorded by the system. The system monitors environmental data such as temperature, supply electric voltages. Is is found that Supply voltage is stable after improvement of ground system. Temperatures of the system in the observation units are enough low. The low temperature environment is thought to be effective for long-term observation.