[HDS13-P02] Tsunami Data Assimilation of the 2015 Torishima Earthquake
Keywords:Tsunami Data Assimilation, Tsunami Forecasting, Torishima Earthquake
Tsunami data assimilation forecasts the tsunami by assimilating offshore observed data into a numerical simulation, without the need of calculating the initial sea surface height at the source (Maeda et al., 2015). In the Nankai region, the Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) records the water pressure and has real-time data transmission. Synthetic experiments showed that this observational system was able to forecast the waveforms at Shikoku Island by tsunami data assimilation approach (Wang et al., 2018). Here, we performed this method to retroactively forecast the tsunami of the 2015 Torishima earthquake. We assimilated the observations of 16 DONET stations and two ocean bottom gauges off Muroto. The tsunami waveforms at the tide gauges Tosashimizu and Kushimoto were forecasted, and compared with the actual records.
The comparison between forecasted and observed waveforms at two tide gauges suggested that our method could forecast the tsunami amplitudes and arrival time accurately. The tsunami warning could be issued to local residents of Shikoku Island more than one hour before its arrival. Our method is merely based on offshore observations, and could be implemented for future tsunami warning systems.