[J04-4] Geohazard early warning systems IV

[J04-4-04] Synthesis of Offshore Tsunami Records and Inundation Including Seismic Waves and Tsunami: Anticipated Nankai Trough Earthquakes, Southwest, Japan

^○Tatsuhiko Saito¹, Toshitaka Baba², Shunsuke Takemura¹, Eiichi Fukuyama¹ (1.National Research Institute for Earth Science and Disaster Resilience, 2.Tokushima University, Tokushima, Japan)

New tsunami observation networks such as DONET and S-net are designed for the observation inside earthquake focal area. When analyzing the tsunami recorded inside the focal area, seismic waves and tsunami appear at the same time. Theories that describe both seismic waves and tsunami are necessary. Saito and Tsushima (2016) proposed a method for synthesizing ocean-bottom pressure records considering both seismic waves and tsunami, but their method is not applicable to sea-surface displacement records. Recent observation enables us to observe tsunami by sea-surface displacement by using GPS buoys. Inazu et al. (2016) showed that real-time tsunami source estimation is possible if if we utilize high-precision, real-time GPS height observations equipped with cargo ships and tankers. This study shows a method that synthesizes tsunami records of sea-bottom pressure change and sea-surface displacement including seismic waves and tsunami. As examples of huge earthquake, the scenarios of anticipated Nankai-Trough huge earthquakes proposed by Hok et al. (2011) are used. By using their rupture scenarios as seismic sources in seismic-wave propagation simulations, we calculated spatial and temporal variation of the sea-surface displacement without considering gravity (e.g., Takemura et al. 2015). Then, we included the contribution of gravity by numerically solving tsunami equations and also simulated the inundation with high-resolution topography data using JAGRUS (Baba et al. 2015). Seismic waves and tsunami simultaneously appeared in both ocean-bottom pressure change and sea-surface displacement during the earthquake rupture, which would make tsunami analyses difficult. The seismic-wave contribution to sea-bottom pressure records is greater than to the sea-surface displacement. The data sets created in this study would be useful for practical tests of tsunami-prediction algorithms using offshore tsunami records, especially including the records inside the focal area.