An investigation into the ancient documents showed that the strange massive earthquake occurred in 794 (Enryaku 13th years) when the capital relocation to Heiankyo was carried out could be the Nankai earthquake.
Associate Professor Katsunori Imazu (Japanese ancient history) of the Okayama University announced this on the 17th (April). Although it was supposed that the Nankai earthquake had a occurrence cycle of once in about 100 years, the record on this earthquake for about 200 years was not found until now, there was an earthquake buried in that "empty period".
According to Associate Professor Imazu, inside the "Nihongiryaku" (edited at the Heian period) which extracted contents from one of the Japanese official history - the "Nihonkouki", on 10th July in the 13th year of Enryaku there was a description saying that "the Imperial Court, the Kyonggi government residence, and the houses were shaken. There were people died in the quake". Two years afterward, the ancient "Nankaido" highway which was built along the sea in Shikoku was abandoned, and it was recorded that a new road was designed afterwards.
Since the abandonment of the highway presupposed that it was damaged due to a tidal wave caused by a massive earthquake, and that the epicentre area was presumed to be at the Pacific Ocean side, Associate Professor Imazu judged that it was the Nankai earthquake.
This is an interesting historical finding about a tsunami occurred in Japan more than