Possibility of the links between Tokai and Nankai earthquakes indicated by tsunami deposits

Four tsunami deposits have been discovered in the Otagawa Lowlands. Based on radiocarbon dating, they are placed at the late 7th century, the late 9th century, between the11th and the 12th centuries, and between the latter half of the 15th and the early 17th centuries, respectively. The younger two deposits are considered to represent tsunami resulting from the 1096 CE Eicho Earthquake and the 1498 CE Meio Earthquake. In conjunction with historical records, the occurrence of the tsunami in the late 9th century provides evidence for the occurrence of a Tokai earthquake at the same time as the Nankai earthquake of August 22, 887. The tsunami deposit dating from the late 7th century also indicates the occurrence of a Tokai earthquake, but because the date of its occurrence cannot be specified, it is unknown whether it occurred simultaneously with the Nankai earthquake of 684.