Outline of New Cabled Observation System off Toyohashi

A new cabled observation system off the coast of Toyohashi in central Japan is now being developed. The system uses a couple of former underwater optical telecommunication cables of about 60 kilo-meters long. The authors will use the cable in two ways simultaneously. One is to build a new observatory at the end of the cable. Underwater sensors including a broadband seismometer, a precise water-pressure sensor and an electro-magnetometer will be connected to the junction unit using underwater mateable connectors. The other is to use the same cable simultaneously as a long emitting antenna to monitor the electro-magnetic property of the earth crust. We have developed a new time synchronization system. It provides precise 1PPS signal, clock and NMEA data to underwater sensors. In this paper, we will describe the outline of the system. The longterm monitoring will start in this April.