Distributed Acoustic Sensing measurement by using seafloor optical fiber cable system off Sanriku for seismic observation

Recently Distributed Acoustic Sensing (DAS) measurement which utilizes an optical fiber itself as a sensor becomes popular. In 1996, a seafloor seismic tsunami observation system using an optical fiber cable was deployed off Sanriku by Earthquake Research Institute, the University of Tokyo. The system has spare (dark) optical fibers without repeaters. We start development of a seafloor seismic observation system by the DAS technology with Sanriku cable observation system as a next generation of marine seismic observation system. In February 2019, we made a pilot observation of a DAS measurement using a dark fiber of Sanriku seafloor observation system. The data were collected continuously for about 46 hours and many earthquakes including micro-earthquakes and a deep earthquake were recorded.