The 684 Hakuho earthquake took place in Japan in 684, and is described in the history book Nihon Shoki from the 8th century.
It caused the under-sea inundation of approximately 10 km2 (3.9 sq mi) of rice fields.
[2] In this earthquake, the sea reportedly "swallowed up" 500,000 shiro of cultivated land in Tosa Province.
[4] The governor of this province reported the sinking of many ships by a "high-rising great tide" which accompanied the earthquake.
[4] Regarding the flooding, the Nihon Shoki reports that the local people had never experienced a disaster of this type.