The Mature Early Modern View
Bukō Chronicle (Bukō nenpyō) is a record of major historical events, mainly in Edo, compiled by Saitō Gesshin (1804–1878) in 1848 with some additions in 1878. Gesshin was an academically inclined neighborhood head in Edo. His account of the 1703 Genroku earthquake is a good example of an educated person's understanding of earthquakes in mid-nineteenthcentury Japan. Gesshin describes strong thunder during the evening prior to the earth roaring “like thunder” at the eighth hour that night. He describes houses undulating like boats and fissures in the ground as large as six shaku (roughly six feet) that blew out sand or water. Soon after the eighth hour, four tsunami waves swept in and out of the rivers. Aftershocks continued frequently for about a week. Following this description, Gesshin includes a line of verse from the imperial court poet Naka-no-in Michishige (1631–1710): “The rock of the thousand generations of the country's kami will not be shaken down by pulling on the immovable August Reign.” As we have seen, verses emphasizing the stability of the country's foundations, usually in the form of kami and the imperial court, were common in the wake of major earthquakes. Of course, Gesshin summarized this earthquake from documents, and the purpose here is to note the language and concepts he employed from his circa 1848 vantage point. Rain Dampened Sleeves (Shigure no sode) is an account of events and lore connected with the Ansei Edo earthquake compiled by Hata Ginkei. The chapter discussing earthquakes provides a useful glimpse of the knowledge available to well-read Japanese around 1855. It consists mainly of a summary of different theories and topics, but Ginkei's own ideas also guide the discussion. He discusses wind as a source of the trapped yang energy that causes earthquakes and points out that fierce wind accompanied an earthquake in the Kantō area in 1648. Subsequent sections include quotes from Illustrated Compendium of Chinese and Japanese Knowledge, a Chinese astronomy text, Chronicles of Japan (Nihongi or Nihonshoki), and several passages from Thoughts on Earthquakes. Ginkei includes a diagram of an earthquake's epicenter, extensive discussion of signs of an impending earthquake, and a discussion of earthquake divination. Rain Dampened Sleeves does not present new theories, but Ginkei assembles and summarizes in one place nearly all of the accumulated knowledge about earthquakes to date. Ginkei also provides an interesting explanation of how catfish came to be associated with earthquakes. From far back in the past, children imagined a giant catfish to live under the earth and cause earthquakes when it moved its whiskers (hige). Although the catfish idea is “utter nonsense,” the likely explanation for it is that the na in namazu (catfish) is the same na as in nai (earthquake). Furthermore, speculates Ginkei, hige (whisker, beard) and hire (fin) became confused. Therefore, catfish whiskers became associated in children's lore with earthquakes.
Ansei Record was a widely read journalistic account of the Ansei Edo earthquake. Its explanation of earthquakes, which appears in the initial part of the section “Jishin no ben” (Earthquakes explained), should be tediously familiar by now. It begins with the Astronomy Questions Answered–derived explanation that heaven and earth are full of holes like a bees' nest or the cap of a mushroom. The basic mechanism is that fire energy seeks to rise but is blocked by water energy—the same logic as thunder in the heavens. Moreover, Ansei Record provides exactly the same geographical explanation as previous texts regarding the frequency of earthquakes with respect to the North Pole, the equator, and warm areas with rocky soil. One point about the causal mechanism of earthquakes is an explanation that although Edo experiences frequent small earthquakes, the relative absence of large ones is because of the presence of many wells. These wells ordinarily provide yang energy with an escape route. This point was important, as we will see. By 1855, the basic idea of yang energy within the earth seeking to rise but blocked by yin had long been the dominant commonsense mechanical cause of earthquakes. Moreover, well-read Japanese of this time with an interest in natural science would likely have been aware of aftershocks, liquefaction, sand and mud blows, uplift, epicenters, and subsidence. They also had a vague sense of hypocenters and seismic waves, the knowledge that shaking diminishes farther from the epicenter, and that the severity of ground motion varies as a function of the soil base. Furthermore, tsunamis and volcanism were both understood as closely connected with earthquakes. In short, careful observation within an increasingly literate society had established a solid foundation of geophysical knowledge. The major gap in this knowledge, of course, was an understanding of faults and plate tectonics, two concepts that would not become known and accepted anywhere in the world until the early and later twentieth century respectively. In the absence of this knowledge, yin-yang–based descriptions of earthquakes had great explanatory power.
Other important components of the late Tokugawa-period view of earthquakes included an assumption that earthquakes and thunder were both the same basic phenomenon. Moreover, in academic circles there was an increasing interest in the possibility that electricity might be the key to explaining earthquakes. Most Japanese at this time thought earthquakes had connections with atmospheric phenomena, especially wind. Smoke, steam, other emissions of heat from the ground, unseasonably warm weather, and brightly glowing stars and the moon, especially with a reddish tint to them, were all signs of earthquakes, albeit always recognized after the fact. The basic idea behind all of these supposed precursors was yang energy rising from the earth. If this energy could be vented to the surface effectively, all would be well. If it became bottled up, explosions and shaking, accompanied by the expected sound and light effects, were the likely results.
-  Saitō Gesshin, Bukō nenpyō 1, Tōyō bunko #116, Kaneko Mitsuharu, comp., ed. (Heibonsha, 1968, 1992), 103.
-  Hata Ginkei, Shigure no sode, part 2 (kōhen), vol. 1, in Edo sōsho kankōkai, ed. Edo sōsho, vol. 10 (Meicho kankōkai, 1961), 107–122.
-  Hata, Shigure no sode, 110.
-  AKR, vol. 1, 1 (jō no ichi). See also Arakawa, Jitsuroku, Ō-Edo kaimetsu no hi, 24–25. According to Andrew Markus, “One theory . . . maintained that Edo was permanently immune from the danger of earthquakes, since a vast number of wells . . . provided more than adequate venting for pent-up ‘vapors’ in the earth.” See “Gesaku Authors and the Ansei Earthquake of 1855,” in Dennis Washburn and Alan Tansman, eds., Studies in Modern Japanese Literature: Essays and Translations in Honor of Edwin McClellan (Ann Arbor: Center for Japanese Studies, University of Michigan, 1997), 55.
-  Subsidence often appeared as “breaking” (yabure sōrō), especially in early texts. For example, in 1662 the edge of the moat of Osaka Castle “broke” by one shaku. See “Gen’en jitsuroku,” in DNJS, vol. 1 (kō), 249. After describing damage to samurai and commoner structures in the Obama domain of Wakasa, one passage explains that “there was ‘breakage’ to the extent of 3 or 4 shaku, from which mud flowed” (250).