A basic study of utilization of DBF ocean radar with VHF BAND for tsunami detection in open sea

After 2011 Tohoku-Pacific Ocean earthquake, Chubu Electric Power Co., Inc. has been voluntary addressing to build the tsunami observation network at Hamaoka nuclear power station mainly utilizing an ocean radar, the GPS-mounted Buoy, the submarine cabled real-time seafloor observatory system and a highly sensitive camera. The purpose of this study is to evaluate the basic usability of the VHF ocean radar through field observation in front of Hamaoka nuclear P/S, and to investigate short time variability of coastal currents under the natural condition for construction of tsunami warning system. High acquisition area of valid current data of the ocean radar varied from 13 to 17 km off the observation site in the radial direction, which suggests the maximum detection range of tsunami by the ocean radar in this sea area. The comparison of the current data by the ocean radar with the current meter resulted in the correlation coefficient of about 0.8 in radial direction, and the correlation improved after reducing the wind-driven effect by the multiple regression analysis with the wind data. As the temporal variability of coastal currents to 1-hour interval was almost about 5 to 10 cm/s, the current anomaly excited by tsunami greater than 10 cm/s seems to be detectable by the ocean radar in this area.