Paper short abstract:

This paper deals with the natural disasters that marred the final years of Tokugawa Tsunayoshi's government with focus on the earthquake of Genroku 13 (1703). The paper will explore why this 8.2 magnitude earthquake, causing a change in era name, finds little mention by historians.

Paper long abstract:

Historical markers are essential for historians for they define the scope of their work. Since they are also political statements, their determination has been the preserve of power holders for the greater part of history writing. In Japan historical markers were generally set by a change in era name, and the case of the competing Northern and Southern Courts of the fourteenth century, each setting their own era names, is a case in point.

With the assumption of the Tokugawa regime, changes in era name became the prerogative of the shogun, and were often used to break the chain of unfortunate events, hoping to persuade the gods that a new era had begun. Thus the 8.2 magnitude Genroku 16 (1703) earthquake with a tsunami washing away whole villages along the coast of present-day Chiba, Shizuoka and Kanagawa prefectures and a death toll of over 200.000 people, resulted in a change of era name to Hōei. Yet natural calamities continued for the remainder of the fifth shogun's government, peaking in the most violent recorded eruption of Mt. Fuji of Hōei 4 (1707).

The change in era name to Hōei thus provides a convenient historical marker in dividing the government of Tokugawa Tsunayoshi (1680-1709) into an era of increasing prosperity and social development peaking in the Genroku period (1688-1703) and the final six years of his government when the extreme conditions produced by natural disasters had to be dealt with. Traditional Japanese historiography, however, has divided Tsunayoshi's government in to the "sober" period of government under the control of the grand counsellor Hotta Masatoshi corresponding to the Tenna era (1681-1684) and the "corrupt" chamberlain government of the remaining period. The Genroku earthquake, though stronger and claiming more lives than the so-called Great Kantō earthquake of 1923, finds little mention in history books, and the disastrous 1707 eruption of Mt. Fuji has only recently received some attention though mainly from volcanologists, since a new eruption is due.

The paper argues that the traditional interpretation is based on "alternative facts" and that environmental facts are a more reliable source for the historian.