Early Modern Academic Theories of Earthquakes
Between 599 and approximately 1990, over forty-five thousand instances of felt earthquakes appear in extant records. Approximately 1.1 percent of these records are from the period of 599 until 1600, and 89 percent of them are from the Tokugawa period. This sharp increase in the documentary coverage of earthquakes corresponds with the emergence in the seventeenth century of specific theories about their causes. During medieval times, earthquakes were but one variety of “earthly anomalies” (chii). During the Tokugawa period, earthquakes became an object of academic study in their own right. Although there was considerable overlap and cross-influence, academic theories of earthquakes tended to fall into three categories based on the origins of their theoretical frameworks: Buddhist, Western, and Chinese. Theories based on a Chinese-derived yin-yang framework became most influential as time went on.
Basic Buddhist Theory
During the seventeenth century, Buddhist cosmology often supplied material to explain earthquakes. The anonymous 1662 Supreme Ultimate Earthquake Record (Taikyoku jishinki), another product of the Kanbun earthquake, was particularly influential. Although it explains earthquakes from a Buddhist cosmological perspective, the work also contains extensive quotations from Confucian and Daoist writings. Buddhist explanations of earthquakes typically start with the Five Seed Elements of earth, water, fire, wind, and space. As for the structure of the earth, “above space is wind. The agitation of wind causes it to blow upward, likewise agitating fire. When fire becomes well agitated, water is no longer calm, and it functions as a substance [ki] that can long support things floating on it. Therefore, it is easy for the earth to float atop water. The power of the fire and wind below causes the water to surge upward, and the earth serves as a lid to hold the water down.” The element space is found in the heavens, and the deepest layer of the earth is wind. This wind feeds fire, the next layer, which boils the water above it, which supports the earth. The above passage describes the normal state of affairs, with upwelling forces and downward suppressing forces in equilibrium, much like yin and yang balancing each other.
What preserves this balance? According to Supreme Ultimate Earthquake Record, it is “the ki of the two kami,” with ki indicating matter or material force (Chinese: qi) in the context of Chinese cosmology and the kami as willful cosmic forces. Ominously, “When the people offend against the will of the kami, that offense penetrates heaven and earth.” The anger of the deities whips up a divine wind that can manifest itself as earthquakes, typhoons, floods, severe waves, or poor agricultural conditions—among other problems. Notice here the key role of human behavior in influencing the cosmic forces. In this respect, little had changed from medieval conceptions of natural hazards.
Supreme Ultimate Earthquake Record explains the basic mechanism of earthquakes in several variations, striking what we might call a scientific tone in some places and focusing on moral qualities in others. For example, “Earthquakes are the result of abnormal transformations within the earth, water, fire, and wind.” After proposing the metaphor of water boiling in a pot, the text explains that the mechanics of earthquakes are the same everywhere under heaven. Other metaphors come into play to make the same basic points, reiterating that earthquakes, typhoons, and floods share the same root cause, namely “abnormal transformations of ki.” In what became a common feature in essays on earthquakes during the Tokugawa period, Supreme Ultimate Earthquake Record provides a list of fifteen major earthquakes starting with one in 416, the earliest recorded earthquake in the Japanese islands, and ending with the Kanbun earthquake of 1662. Subsequent paragraphs describe earthquake lore, reiterate the point about earthquakes being caused by transformations of ki, and point out that space or emptiness is the root of the way.
The final paragraph in Supreme Ultimate Earthquake Record includes the rhetorical question, “If we reject the seeds of ethics and promptly forget the way of the kami, will not the state perish?” Subsequent sentences shift the focus from the negative consequences in the question to the benefits of correct behavior and mindset. The dominant metaphor is a mirror, whose essence remains unchanged and that reflects reality without distortion or bias. The final image is of the sun and moon shining brightly, in harmony with people whose pure minds reflect divine virtue. In such a state, “What fear need we have of earthquake anomalies?”
This ending is similar Ryōi's attempt to reassure readers that the future looks bright. In another similarity between the two contemporaneous texts, Ryōi provides a brief description of over twenty past earthquakes starting in 416, including some that occurred in China. Immediately after this description, there is a concise explanation of the Buddhist view of earthquakes, which differs slightly from Supreme Ultimate Earthquake Record. Wind is the deepest layer in Ryōi's summary, but instead of nurturing fire, the wind agitates a layer of water. The gold layer is located above the layer of water, and earth forms the outermost layer. Vigorous movement of the wind can agitate all of the other layers, thus causing an earthquake. Ryōi's explanation is entirely mechanical, with no mention of moral issues or human behavior.
-  Kitahara Itoko, ed., Nihon Saigaishi (Yoshikawa kōbunkan, 2006), 161, and Ueda Kazue and Usami Tatsuo, “Yūshi irai no jishin kaisū no hensen,” Rekishi jishin 6 (1990): 181–187.
-  Taikyoku jishinki, in Aoki Kunio et al., eds., Taikyoku jishinki, Ansei kenbunroku, Jishin yobōsetsu, Bōkasaku zusetsu, Edo kagaku koten sōsho, vol. 19 (Kōwa shuppan, 1979), 12. See also Hashimoto, Jishingaku, 11–12, and Nihon gakushiin, Butsuri kagakushi, 534–538.
-  Taikyoku jishinki, 12.
-  Ibid., 15.
-  Ibid., 17.
-  Ibid., 18.
-  Ibid., 19.
-  Ibid., 20.
-  Asai Ryōi, Kaname’ishi, 66–70.