Design of deep ocean submarine cable observation network for earthquakes and tsunamis

A scientific submarine cable network called DONET (Dense Ocean-floor Network System for Earthquakes and Tsunamis) is going to be built in the rupture area of Tonankai earthquake in the south of Kii-peninsula, Japan. By the DONET deployment in the seafloor, we expect significant improvement of location accuracy of micro earthquakes. Also, we expect to identify occurrence of slow slip event of moment magnitude of 6 in the seafloor. Observation of such events requires precision seismic and seafloor pressure measurement in wide dynamic range and broad frequency band for DONET observation sensors. We plan to combine broadband seismometer and strong motion accelerometer, quartz pressure gauge, a differential pressure gauge, and hydrophone installed in each observatory. To choose seismometers to be incorporated for the DONET observatory, we evaluated noise characteristics of seismometers of different kind in land vault. Also, we evaluated quartz pressure gauges for their long-term stability in seafloor environment.