Early and medieval theories of natural Hazards and disasters
The general term for the Chinese idea that natural calamities were heavenly warnings or punishments for a lack a virtue on the part of the ruler is zaiyi sixiang (Japanese: saii shisō). The zai of zaiyi included events such as droughts, floods, famine, insect infestations, fires, and rebellions, and yi indicated portents such as eclipses, earthquakes, unseasonable weather, and abnormal plants and animals. This basic concept was present in Japan by the time of the formation of the Ritsuryō state in the eighth century, and it coexisted with an alternative understanding of natural and social disasters as curses (tatari) from the kami. Because early conceptions of the kami usually regarded them as inscrutable and arbitrary in their violence, this alternative understanding conflicted with the view that natural disasters were signs the sovereign or state was deficient in virtue.
Early Japanese emperors typically took responsibility when natural hazards caused major loss of life or destruction, but formal declarations typically deemphasized any lack of virtue on the part of the sovereign. Instead, the focus of imperial responsibility was enacting corrective measures such as intoning sutras at major temples. The typical arsenal of corrective actions included donations to major shrines and temples, mobilizing temple and shrine priests, declaring a general amnesty, and distributing rice and salt to the poor. Other measures might include rebuilding destroyed dwellings, ensuring proper burial of the dead, exempting those above age sixty from labor service, imperial edicts exhorting officials to be mindful of their duties, and changing the era name. Some of these elements remained part of official responses to calamities even during the nineteenth century. In the wake of the Ansei Edo earthquake, for example, the bakufu mobilized the religious power of shrines and temples and provided material relief to retainers and townspeople.
During medieval times, Buddhist cosmology tended to condition thinking about natural hazards and disasters. The basic idea was to link good or evil behavior in the realm of humans with the balance of power between good and evil deities. In this view, the conflict between good and evil deities controlled natural phenomena on earth. Japan's kami became avatars of buddhas and bodhisattvas, and, as such, the kami became more rational in the sense of behaving predictably according to moral standards. Insofar as human behavior could influence the kami for better or worse, it could increase or reduce the severity of natural hazards. In Treatise on Securing Peace for the Country (Risshō ankokuron, 1260), for example, Buddhist thinker Nichiren explained that when people turn their back on the True Law and embrace the Wicked Law, a variety of problems plague a country. These problems include abnormalities of the sun and moon, abnormalities of the stars, fires, floods, windstorms, droughts, external military invasions, famine, warfare, and epidemic disease. In one part of the essay, Nichiren explains that when the principles of Buddhism become obscured and lost, “at that time, loud noises will sound in the air and the earth will shake; everything in the world will begin to move as though it were a waterwheel. City wells will split and tumble, and all houses and dwellings will collapse. Roots, branches, leaves, petals, and fruits will lose their medicinal properties. . . . The crops will all wither and die, all living creatures will perish, and even the grass will cease to grow any more. Dust will rain down until all is darkness and the sun and the moon no longer shed their light.” In Nichiren's Treatise and many other Buddhist writings, earthquakes are part of a larger package of possible calamities including the complete destruction of human society.
The most common Buddhist texts deployed in attempts to prevent or minimize the effects of malevolent cosmic forces were the Heart Sutra(Daihannya-kyō) and the Benevolent King Sutra (Ninnō-kyō). In 1231, for example, the Kamakura bakufu ordered thirty priests to intone the Heart Sutra at the Tsuruoka Hachiman Shrine at the height of the Kangi Famine. Another common text for guarding against natural disasters was the Golden Light Sutra (Konkōmyō-kyō).
-  Mizuno Shōji, “Chūsei no saigaikan,” in Kitahara Itoko, ed., Nihon saigaishi (Yoshikawa kōbunkan, 2006), 97–98. For a detailed discussion of Chinesederived tenjin-sōkan (heaven and human interconnection) thought in the context of earthquakes in Japan, see Hagiwara et al., Kojishin, 43–47. Regarding countermeasures, see 44–45, 46–47. For a discussion of era name changes because of earthquakes, see 46–47 and Nihon gakushiin, eds., Meiji-zen Nihon butsuri kagakushi (Nihon gakjutsu shinkōkai, 1964), 501.
-  Mizuno, “Chūsei,” 98–99, and Imahori Ta’itsu, “Kokudo no saigai to akukishin: Saigai to zokushin,” in Inseiki bunka kenkyūkai, eds., Seikatsushi (Inseiki bunka ronshū, vol. 5), 198–232. According to the Niō Sutra, for example, “Disorder among the deities leads to disorder in a country. Because the deities are in disorder, so too are the masses of people” (Imahori, “Kokudo no saigai,” 224).
-  Philip B. Yampolsky, ed., Burton Watson et al., trans., Selected Writings of Nichiren (New York: Columbia University Press, 1990), 16. For the full discussion, see 13–21. See also Mizuno, “Chūsei,” 99, and Imahori, “Kokudo no saigai,” 220–226.
-  Azuma kagami, Kangi 3, 5m 17d. “To attain peace in the realm and a bountiful harvest for the country, from today, at the Tsuruoka Hachiman Shrine, thirty priests will intone the Dai hannyakyō.” (http://www5a.biglobe .ne.jp/~micro-8/toshio/azuma/123105.html, accessed February 14, 2011). See also Mizumo, “Chūsei,” 100–101, and Hagiwara et al., Kojishin, 46.
-  Herman Ooms, Imperial Politics and Symbolics in Ancient Japan: The Tenmu Dynasty, 650–800 (Honolulu: University of Hawai‘i Press, 2009), 90.