安政2年9月28日 (1855-XI-7) の遠江沖地震について

抄録

In the evening of November 7, 1855, a large earthquake occurred beneath the sea off the southern coast of the Tokai district, central part of the Honshu Island. Recently more than fifty kind of historical documents were discovered, and we obtained much amount of knowledge about it. Most serious damages occurred in several villages on the coast in the vicinity of Hamamatsu City, where destruction of houses and gushing of sand were reported. Shock of intensity IV (in JMA scale) was experienced in the western part of Shizuoka Prefecture and at several cities on the east coast of the Kii Peninsula. After the occurrence of the earthquake, a small tsunami was generated, and was observed at the Shimoda Port near the tip of the Izu Peninsula, and at three ports on the east coast of the Kii Peninsula, where inundation height was one to two meters. The coast was upheaved near the mouth of the lake of Hamana where it had been subsided with the occurrence of the Ansei Tokai Earthquake of December 23, 1854. In contrast to that, the coast near the cape of Omaezaki was subsided with this earthquake, which had been upheaved with the Ansei Tokai Earthquake.
The estimations of the location of the epicenter and the magnitude were made by adapting least mean square method to the formulae which give the relationship between the magnitude and the area of intensities IV, V, and VI. The location of the epicenter and the magnitude are estimated 34.5°N, 137.8°E and M=7.1, respectively.