A study on the optimal instrumentation region and data processing for tsunami detection in the eastern and southern sea of Korea

Abstract

A tsunami is a significant coastal hazard that causes destructive damage to coastal cities in the world. On the west coast of Japan, tsunamis were generated and damaged eastern coastal cities in Korea in 1983 and 1993. In recent years, there has been an increasing interest in the issue the potential tsunami zone exists near the west coast of Japan and the Ryukyu trench. Therefore, it is important to have tsunami observation instruments in proper location and effective algorithms for noise canceling and tsunami detection. Meteorological Agency has established a tsunami warning system in response to the unanticipated occurrence of potential tsunamis. Although Ulleung-do surge gauge, which is the top priority among the tsunami observation instruments in Korea, observed the 2011 Tohoku tsunami, the tsunami warning was not performed in real-time because the tsunami detection algorithm was not established at that time. Therefore, recently the Korea Meteorological Administration proposed a Tsunami Arrival time Detection System (TADS) for the Ulleung-do surge gauge. However, TADS cannot extract tsunami signals when tsunami signals overlap noises caused by bad weather and electronic communication. Therefore, this study proposes a tsunami detection algorithm considering the characteristics of the Korean tsunami observation instruments. Considering the aspects of noise recorded by the Ulleung-do surge gauge, this study suggested a logical slope-median filter based on the logical median filter of the previous study and the method successfully removed spike-type and bar-type noise of the Ulleung-do surge gauge. This method also shows that it is applicable to other tsunami observation instruments, including the Deep Ocean Assessment Reporting of Tsunamis operated by the U.S.A. as well as the Ulleung-do surge gauge. Several tsunami observation networks have been operated in the world to reduce the damage of unanticipated devastating tsunamis. However, all of tsunami observation instruments operated by Korea is located on the coast, so it is impossible to detect and issue tsunami warning based on observation before tsunamis reach the coast. Therefore, it is necessary to develop a tsunami early warning system for detecting tsunami by offshore tsunami observation instrument in Korea. This study aims to propose an optimal region of offshore tsunami observation instrument deployment for tsunami detection in Korea with efficiency. This study examines how the higher probability of tsunami detection with the minimum instruments and the maximum evacuation time. To suggest the optimal region, both numerical modeling, Cornell Multi-grid Coupled Tsunami (COMCOT), and probabilistic theory were used in this study. Finally, this study suggested the optimal region of instrument deployment for tsunami detection is northeast of Ulleung-do in the eastern sea of Korea and the southern boundary (126.7-127.5°E,32°N) of Korean territorial sea.