ABSTRACT

In this paper, we conducted study of tsunami inundation forecasting in Aichi and Mie Prefecture, Japan. In this study, a database that consists of precomputed tsunami inundation and waveform from multiple scenarios is developed. This method is divided into two stages. In first stage, preliminary earthquake information is used to find appropriate tsunami inundation scenario in database. In second stage, a real-time tsunami waveform simulation is conducted to find best scenario by comparing computed tsunami waveforms and those in database. Furthermore, this method can produce good tsunami inundation forecast in a reliable time.

INTRODUCTION

The 2011 Tohoku earthquake caused more than 15,000 people died and missing (Kazama and Noda, 2012). About 3 min after the earthquake, Japan Meteorological Agency (JMA) announced tsunami warning and advisories for along the coast of Hokkaido to Kyushu and the Ogasawara Islands (Ozaki, 2011). To calculate and determine earthquake hypocenter coordinate and magnitude, JMA utilizes real-time seismic data. By using this system, earthquake information can be obtained shortly after earthquake, but the system underestimated magnitude of the 2011 Tohoku earthquake (Gusman and Tanioka, 2015). JMA estimated initial earthquake magnitude was Mjma 7.9 obtained within 3 min after earthquake. Then, it is revised to be Mjma 8.4 in more than 1 h after earthquake (Ohta et al., 2012). Further study revealed that those magnitudes underestimate actual earthquake magnitude Mw 9.0 (e.g. Gusman et al., 2012; Satake et al., 2013).

The future Nankai Trough earthquake is expected to be occurred in the near future and more destructive than the 2011 Tohoku earthquake. Ishibashi (2004) explained that great earthquake has recurrence interval of 100–200 years based on historical records. Compared to the other earthquake zones in Japan, the Nankai Trough located very near to the coast (less than 150 km) (Mulia et al, 2017). If an earthquake followed by tsunami occurred, tsunami wave would require short time to reach the coast. The 1944 Tonankai and the 1946 Nankai earthquake are the last two earthquakes in Nankai Trough zone followed by tsunami that causing severe damages in southeast of Japan. The estimated seismic moment of the 1944 Tonankai earthquake is 2.06 × 1021 Nm (Mw 8.1) (Baba et al., 2006). This earthquake generated large tsunami with maximum inundation up to 2.8 m as observed in Owase city during field survey (Hatori et al., 1981). The 1946 Nankai earthquake was a shallow earthquake (4.1 km hypocenter depth) with magnitude of Mjma 8.0. More than 11,000 and 1,500 houses were collapse and washed away, respectively by tsunami with maximum wave height of about 6 m (Murotani et al., 2015).

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