Detection of Kuril subduction-zoneearthquakes from remote historic recordsin Honshu, Japan, between 1656 and 1867

Abstract

Earthquakes before A.D. 1800 along the Southern Kuril trench, although before the start of written history on nearby islands, probably account for some of the earthquakes noted by local records in Honshu, hundreds of kilometers to the southwest. Earthquake historians have identified about 4800 felt earthquakes in Edo (present Tokyo) and about 3000 felt reports in selected local government records in Tohoku, northern Honshu, for the years A.D. 1656-1867. On the average, 19 earthquakes per year were felt in Edo. Of the Tohoku records, 361 (an average nearly 2 per year) were felt at multiple Tohoku locations; 95 of these (0.4 per year) were also felt in Edo. Since 1926, Tokyo has had a yearly average of 15 felt earthquakes with seismic intensity 2 or more on the Japan Meteorological Agency scale (corresponding to III or more on Modified Mercalli scale). For Tohoku the average annual frequency is about 4. Among them, an average of 0.6 events per year also reached intensity 2 in Tokyo. About one quarter of these events occurred in the southern Kuril trench. If the seismicity is temporally constant, about 80 of the earthquakes recorded in 1656-1867 probably had a Kuril origin.