European Ideas about Earthquakes
Greek thinker Anaximenes of Miletus (586–528 BCE) saw the earth as full of holes, like a sponge. Rainwater filled these holes and accumulated. When obstructions blocked the rising waters, the accumulated pressure could cause earthquakes. Moreover, when this water dried up, it caused the earth to crack, which caused mountains to collapse, making the earth shake. Democritus (ca. 460–ca. 370 BCE) thought that groundwater displacement was the basic cause of earthquakes. In his view, the earth was originally full of water and excessive rains might cause this water to overflow, thus triggering earthquakes. When parts of the earth dried out, large quantities of water rushing into the dry area could also cause earthquakes. Aristotle (384–322 BCE) was doubtful of these explanations. For one thing, even constantly dry regions experience earthquakes, and if Anaximenes was correct, the earth's surface would gradually become more level and the frequency of earthquakes would diminish.
Aristotle's view of earthquakes came to Japan via Christian missionaries in the late Muromachi period and remained influential during the Tokugawa period. For Aristotle, wind was the main cause of earthquakes, and he saw the world as consisting of five elements: fire, earth, air, water, and ether. This obvious resemblance to theories of earthquakes based on Buddhist cosmology, along with imprecise translation, resulted in theories of earthquakes based on Aristotle often appearing to be of Buddhist origin. The first systematic explanation of earthquakes in Japan was Alpha and Omega Explained (Kenkon bensetsu), first written in roman letters in 1650 and rewritten in Japanese script in 1659. “Kenkon” is the Japanese pronunciation of the Chinese qian-kun, the pure yang and pure yin trigrams in the Classic of Changes (Yijing). The original author of Alpha and Omega Explained was Sawano Chūan, formerly Christovao Ferreira, who lived in Japan for forty years. His work was based on a European astronomy book that a Japanese official obtained from Portuguese priests undergoing interrogation in 1643. True to its title, the work explains a wide variety of natural phenomena. One chapter deals with earthquakes, and the explanation is basically Aristotelian: “That which we call an earthquake is the result of bursts of wind entering the large holes in the earth and becoming trapped there. Because this collected wind is located under subterranean water, when it tries to escape from the earth it can find no suitable path. The force of the wind trying to escape causes the earth to shake.” There is an obvious resemblance to the action of wind and water previously described in Buddhist theories.
The work goes on to specify additional mechanisms. One possibility is that when wind does escape through the earth's large holes, the air below has the qualities of being warm and damp, whereas the earth has the opposite qualities of being cold and dry. The conflicting qualities can cause the earth to shake. In cases when the opposite qualities blend harmoniously, the escaping yang-air (called eisarasan) becomes hot and dry. When wind blows anew, this new wind and the escaping hot and dry air are in conflict, and the new wind pushes the escaping air back, causing the earth to shake. Another possible cause of earthquakes is a large quantity of this accumulated hot and dry air. Because it naturally seeks to rise, this air can cause the earth to shake. Islands and areas along rivers are especially prone to earthquakes owing to these forces.
Many Tokugawa-era scholars were aware of both classical and more recent European theories of the earth and planets. The prolific philosopher and astronomer Miura Baien (1723–1789), for example, made reference to the ideas of Hipparchos (second century BCE), Ptolemaios (Claudius Ptolemy, second century), Nicolas Copernicus (1473–1543), and Tycho Brahe (1546–1601).
-  Hashimoto, Jishingaku, 7–8, and Guidoboni and Ebel, Historical Seismology, 148–149.
-  Quoted in Nihon gakushiin, Butsuri kagakushi, 533. Regarding Kenkon bensetsu, see 532–524 and Hashimoto, Jishingaku, 13.
-  Nihon gakushiin, Butsuri kagakushi, 533, and Hashimoto, Jishingaku, 13. According to Hashimoto, these Kenkon bensetsu explanations are modifications of Aristotle’s original theory.
-  Miura Baien, Zeigo, in Yamada Keiji, ed., trans., Miura Baien, Nihon no meicho 20 (Chūō kōronsha, 1984), 454.