[S-CG63] Reducing risks from earthquakes, tsunamis & volcanoes: new applications of realtime geophysical data

[SCG63-06] Toughening disaster prevention for each region using scientific information on real-time crustal activities, prediction and hazards

*Narumi Takahashi¹, Naotaka YAMAMOTO CHIKASADA¹, Yoshinobu Mizui¹, Rika Otsuka¹, Kentaro Imai², Ryoko Ohbayashi², Hiroshi Osada², Masahisa Oyaizu², Kentaro Nakai³, Yoshiyuki Kaneda⁴, Atsuko Nonomura⁴, Mari Takahashi⁴, Toshitaka Baba⁵, Junko Kanai⁵, Kazuyoshi Nanjo⁶, Mayumi Sakamoto⁷, Anna Matsukawa⁷, Kan Shimazaki⁸, Kohei Takahara⁹, Jun Kawaguchi¹⁰, Yuji Kobayashi¹¹, Shuichi Kodaira² (1.National Research Institute for Earth Science and Disaster Resilience, 2.Japan Agency for Marine-Earth Science and Technology, 3.Nagoya University, 4.Kagawa University, 5.Tokushima University, 6.University of Shizuoka, 7.University of Hyogo, 8.Kinki University, 9.National Institute for Land and Infrastructure Management, 10.Mie University, 11.Oita University)

Keywords:Nankai trough earthquake and tsunami, crustal activity, hazard, literacy for disaster information

One of the most important concern for residents living along the Pacific coast is the Nankai Trough earthquakes and tsunamis, To contribute for them, a Research project for Disaster Prevention on the great Earthquakes along the Nankai Trough continued until March, 2025. As a part of the project, we have carried out studied about establishing disaster images through information of activities of the Nankai trough earthquakes and tsunamis. Our main activities consist of three items, which are re-evaluation of hazards using realistic strong motions and tsunamis, discussion for sharing disaster prevention on each local region using cutting edge technologies and science, and improvement on literacy for disasters. Here, we present contents of these studies, and how these results contribute to local regions.
For re-evaluation of the hazards, one of issues is deformation of river embankments. Current strong motion waveform used for the evaluation should have long duration time with low frequencies. In addition, the 2D heterogeneous ground structure until basement rocks should be also considered. Some areas where mouths of large rivers concentrate may have larger risks for the subsidence of the embankments than current hazards. The second is tsunami debris. Tsunami debris tends to accumulate around upper limit of the inundation area and tsunami fire may be brought. Shallow inundation areas must not be regards to be safety areas. Here, we present some examples of debris accumulation (Imai et al, 2022) and drift of the debris (Kozono et al., 2016). These images of tsunami debris mapping are important for estimation of the damage level. Local government can also know not only concrete damages by the Nankai trough earthquakes and tsunamis in advance using such simulation technology but also priority of policies for disaster prevention. For example, health of infrastructures and difficulties of access are imaged. As the third, some local governments implement a real-time tsunami prediction system using real-time data for earthquakes and tsunamis (Takahashi et al., 2017). Recently, we transfer how to use it for reduction of damages, and rescue residents damaged by tsunamis to users supporting risk managements. Above issues we mentioned, should be customized for each character through drills.
Such local characters of disaster prevention should be shared among municipalities having similar characters. We have held a meeting twice per a year with four themes, which are re-evaluated hazard, complicated disasters by earthquakes, tsunamis, meteorological disaster and so on, business continuity plan after disaster, and education for future local region supporters. Through the meetings, we obtained common items to overcome disasters, which are diversities for scenarios, optimization of the prevention considering complicated disasters, establishment of close communities, customized preparation for evacuation and reconstruction in advance, and disaster education. To recognize the risks correctly, understanding current crustal activities and vulnerability of disaster prevention for each area is indispensable. We constructed sharing system for crustal activities and hazard information for an entire area along the Nankai trough. Spatial-temporal distributions of seismicity and slow slips are visualized on the hazard information with active fault distribution. It has options to compare between the seismicity and crustal structure, therefore, uses can monitor activities along the plate boundary.
We worked on improvement of disaster literacy using questionnaire survey to confirm the effects. Disaster prevention classes have been also held for high grade children of elementary schools and junior high school students for four years in Kagawa, Kochi and Miyazaki prefectures. Through the class, the effects for improvement of the understanding natural phenomena of earthquakes and tsunamis, mechanism of the natural hazards, risks for strong motions and tsunamis are confirmed. It is expected that the understanding becomes better and better by the continuity of the class. These classes are helpful for appropriate actions for evacuation and supports for surrounded persons, and made accelerate establishment of the knowledge. We also confirmed that it prompts improvement of ability to think evacuation for junior high school students. There are differences on responses by the class among the generation, and the contents of disaster prevention should be customized via the generation. The challenge is to develop effective educational methods that lead not only to knowledge but also to optimal behavior.