New buoy observation system for tsunami and crustal deformation
- PDF / 1,987,869 Bytes
- 11 Pages / 595.276 x 790.866 pts Page_size
- 72 Downloads / 180 Views
SPECIAL ISSUE PAPER
New buoy observation system for tsunami and crustal deformation Narumi Takahashi • Yasuhisa Ishihara • Hiroshi Ochi • Tatsuya Fukuda • Jun’ichiro Tahara Yosaku Maeda • Motoyuki Kido • Yusaku Ohta • Katsuhiko Mutoh • Gosei Hashimoto • Satoshi Kogure • Yoshiyuki Kaneda
•
Received: 31 May 2013 / Accepted: 15 March 2014 / Published online: 27 August 2014 Ó Springer Science+Business Media Dordrecht 2014
Abstract We have developed a new system for real-time observation of tsunamis and crustal deformation using a seafloor pressure sensor, an array of seafloor transponders and a Precise Point Positioning (PPP ) system on a buoy. The seafloor pressure sensor and the PPP system detect tsunamis, and the pressure sensor and the transponder array measure crustal deformation. The system is designed to be capable of detecting tsunami and vertical crustal deformation of ±8 m with a resolution of less than 5 mm. A noteworthy innovation in our system is its resistance to disturbance by strong ocean currents. Seismogenic zones near Japan lie in areas of strong currents like the Kuroshio, which reaches speeds of approximately 5.5 kt (2.8 m/s) around the Nankai Trough. Our techniques include slack mooring and new acoustic transmission methods using double pulses for sending tsunami data. The slack ratio can be specified for the environment of the deployment location. We can adjust slack ratios, rope lengths, anchor weights and buoy sizes to control the ability of the buoy system to maintain freeboard. The measured pressure data is converted to time difference of a double pulse and this simple method is effective to save battery to transmit data. The time difference of the double pulse has error due to move of the buoy and fluctuation of the seawater
N. Takahashi (&) Y. Ishihara H. Ochi T. Fukuda J. Tahara Y. Maeda Y. Kaneda Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan e-mail: [email protected] M. Kido Y. Ohta Tohoku University, Sendai, Japan K. Mutoh G. Hashimoto S. Kogure Japan Aerospace Exploration Agency, Tsukuba, Japan
environment. We set a wire-end station 1,000 m beneath the buoy to minimize the error. The crustal deformation data is measured by acoustic ranging between the buoy and six transponders on the seafloor. All pressure and crustal deformation data are sent to land station in real-time using iridium communication. Keywords Tsunami Crustal deformation Buoy Slack mooring Nankai Trough
Introduction Many large earthquakes (magnitude [7) have occurred along the Nankai Trough. The trough has four rupture segments, named Tokai, Tonankai, Nankai (e.g., Ando 1975) and Hyuganada from east to west. The latest large events were the 1944 Tonankai earthquake and the 1946 Nankai earthquake. Previously, the 1854 Ansei earthquake ruptured Tonankai, Tokai and Nankai segments. Both earthquakes broke the Tonankai segments earlier and the pattern was reappeared in simulation study of rupture pattern of the large earthquakes along the Nankai Trough using crustal st
Data Loading...
