Development and Utilization of Real-Time Tsunami Inundation Forecast System Using S-net Data

One of the causes of enormous damages of the 2011 megathrust Tohoku earthquake (M 9.0) was the underestimation of the first tsunami warning, which was issued three minutes after an earthquake by JMA as well as the insufficient dissemination of the tsunami information to the public due to power failures. To reduce the fatalities due to tsunamis, it is essentially important to deliver prompt and accurate forecast to the on-shore residences. At the time of the 2011 Tohoku earthquake, offshore observations were insufficient. In response to this situation, Japanese government has started to construct the Seafloor Observation Network for Earthquakes and Tsunamis along the Japan Trench (S-net). One of the most important contributions of S-net is that we obtain additional lead time for earthquake and tsunami early warning. To maximize the advantage of S-net, we are developing a new methodology of real-time tsunami inundation forecast system. In our algorithm, we quickly select several appropriate tsunami scenarios that can explain offshore tsunami observations by using multiple indices from the proposed Tsunami Scenario Bank (TSB), which contains offshore tsunami waveforms etc. An advantage of our method is that tsunami inundations are estimated explicitly without any source information, which may have large estimation error. We carry out many calculations to investigate the sensitivities of the source models to coastal tsunami heights along the Pacific coast of Chiba prefecture. Furthermore, we will evaluate and improve our system through the demonstration experiments with local governments.