貞享二,三年(1685,1686年)の三河地震:吉田藩内とその近傍で書かれた新発掘史料による考察 (邦文)

概要

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It is mentioned in several earthquake catalogues of historical earthquakes that two earthquakes occurred in May, 1685 and on October 3, 1686 in the Toyohashi region, central Japan. We have recently found historical documents recording the latter earthquake in the Toyohashi region where previous studies located the epicenter of the 1686 earthquake without documents. Our analysis of the documents suggests that the 1685 earthquake did not occur. The damage recorded in the historical documents on the 1686 earthquake was large in villages on the Pacific side of the Toyohashi region. According to this evidence we consider that the epicenter of the 1686 earthquake may be located near the Pacific coast to the south of the town of Toyohashi. This large earthquake, the magnitude of which is estimated to be about 7, occurred 21 years before the great Hoei earthquake of October 28, 1707 (M=8.4). In the eastern part of Aichi prefecture, including the Toyohashi region and the offshore region of the Atsumi peninsula, moderate earthquakes have recently occurred. It is possible that the 1686 earthquake was a seismic precursor to the great 1707 earthquake. The eastern part of Aichi prefecture and the offshore region of the Atsumi peninsula in Aichi prefecture may be regions where we should carefully observe seismic activity, and other geophysical and geochemical phenomena.