| Co-Investigator(Kenkyū-buntansha) |
HINO Ryota Research Center for Prediction of Earthquakes and Volcanic Eruptions, Faculty of Science, Tohoku University, Assistant Professor, 大学院・理学研究科・地震・噴火予知研究観測センター, 助教授 (00241521)
IMAMURA Fumihiko Tsunami Engineering, Disaster Control Research Center, School of Engineering, Tohoku University, Assistant Professor, 大学院・工学研究科・附属災害制御研究センター, 教授 (40213243)
NAKAMURA Koichiro Research Institute of Electrical Communication, Tohoku University, Research Associate, 電気通信研究所, 助手 (40302236)
HARA Takefumi Koden Electronics Co. Ltd., Special Product Group, Research Engineer, 特機本部, 研究員
DOBASHI Koji Oki Electric Industry Co., Ltd., Electronic & Communication Systems Lab., Research Development Group, Research Manager, 研究開発本部電子通信システム研究所, 主任研究員
|
|---|
| Research Abstract |
An optical hydraulic-pressure gauge for an optical ocean bottom tsunami meter was developed using a frequency, shifted feedback laser with a rolled fiber sensor based on optical frequency domain reflectometry. Measuring the optical path length of the fiber, the hydraulic pressure is calculated. The sensor consisted of an 870 m-long bare dispersion-shifted fiber rolled on a hollow cylindrical aluminum bobbin, and its pressure sensitivity was confirmed as -2.34 10^<-11> /Pa. The accuracy of distance measurement was 10^<-9> using the frequency shifted feedback laser oscillating at 1.55 μm. Then the accuracy of pressure measurement using this system was 62 Pa, which corresponds to a depth of 6.2 mm and is sufficient performance for tsunami-measurement applications.
Moreover, an origin with a field-spread of a tsunami was estimated using the reverse propagation technique analysis. This draws the wave crest lines to the maximum high-water level point and zero-cross point of the first wave of tsunami about each of two ocean bottom tsunami meters, and estimates the intersection as the origin area. As a result of carrying out a simulation about the tsunami network for the Pacific rim, by adding ocean bottom tsunami meters to the Hawaii Islands circumference realized that an origin area could be estimated with less than 20 % of error.
On the coast of our country, human life is taken by tsunami and it is inflicting serious material damage frequently. It is indispensable to damage mitigation by tsunami offering exact information promptly. Real-time multi-point measurement is possible by the multiplexing the laser hydraulic pressure gauge using a frequency-shifted feedback laser. A tsunami numerical simulation can grasp correctly the scale and arrival time of tsunami. If the measurement network by the ocean bottom tsunami meter of a wide area based on this research result is realized, an exact tsunami warning can be issued and it is expected to minimize the damage.
|
