Real-time measurement of deep sea currents off Cape Muroto

A Real-time Seafloor Observatory was developed at JAMSTEC from 1995 to 1996 for the purpose of measuring and monitoring submarine earthquakes and the deep sea environment. It was deployed off Cape Muroto, in western Japan, in March, 1997. The observation system consists of bottom seismometers, a Tsunami pressure gauge and a cable end station. An ADCP (RD Instruments, BB-DR-150) and electro-magnetic current meter (InterOcean, S4D) were attached on the cable end station as environment monitoring instruments. The cable end station is located about 100 km off Cape Muroto, at a depth of 3572 m. Measurement data is transmitted in real-time by using a submarine electro-optical cable. Current profiles are obtained as in layers of about 150 m thickness. The features of the deep currents, the southwestward current, which can be observed in the Nankai Trough on the landward slope in the right hand, is strong. This suggests that existence of a deep boundary current at landward slope of Nankai Trough.