According to a popular Japanese myth the cause of earthquakes is the giant fish Namazu, often depicted as a giant catfish in woodcuts called namazu-e. He is considered one of the yo-kai, creatures of mythology and folklore causing misfortune and disasters. Only the god Kashima can immobilize namazu and with the help of a heavy capstone he will push the fish against the foundations of earth. However the god sometimes got tired or is distracted from his duty, Namazu will use these moments to wiggle his tail, causing an earthquake in the human world.
Fig.1. The god Kashima immobilizes a guilty Namazu, demonstrating to a group of smaller catfishes, representing earthquakes of the past, the severe punishment for their behaviour. The catfishes explain their misbehaviour as results of their envy to other fish species, much more appreciated and popular in traditional Japanese cooking (image in public domain).
Namazu depictions are known since the fifteenth century, however only in the late eighteenth century he became associated with natural disasters. In the Tokugawa period (1603-1868) the giant catfish was as a river deity associated with floods or heavy rainfall. He acts often as a premonition for danger, warns people from an imminent catastrophe or swallows dangerous water-dragons, preventing further disasters. The dragon was a very old and powerful symbol, imported from China, and was considered the main culprit of many sorts of disasters, including earthquakes. During the 18th century the giant namazu gradually replaces the dragon in the role as mischief-maker. This change from the dragon to Namazu was minor, because dragons were also associated to water and rivers and therefore considered closely related to the catfish myth.
During the 19th century and especially after the earthquake of Edo (modern Tokyo) in 1855 the wrongdoings of Namazu were considered more a punishment of human greed, as it was believed that the catfish by causing havoc forces people to redistribute equally their accumulated wealth. Namazu became known as yonaoshi daimyojin, the "god of world rectification".
Fig.2. Namazu-e showing yonaoshi daimyojin perpetuating a traditional suicide ("seppuku namazu", 1855) - with his sacrifice he will provide money, dropping from his belly, for the poor people seen in the background of the image. The scene is supervised by the god Kashima. Some of these anonymous images possess also great magical powers, promising protection from earthquakes and "10.000 years of fortune" (image in public domain).
The classic namazu-e (more than 300 are today known) were a response of the Edo earthquake - by trying to depict also "positive aspects" (the redistribution of wealth) of the earthquake the artists hoped to rise the morals of the survivors. The figure of Namazu was used also in satire; he is shown as a coward hiding from the responsibility of disaster relief, a reference to the aristocracy and incompetent civil servants.
Fig.3. A Namazu, representing the earthquake of Edo (modern Tokyo) in October 1855, is attacked by peasants and concubines, however in the background help for the catfish is approaching - craftsmen, who will take profit from the reconstruction of the city. The earthquake of Edo, which killed thousand of inhabitants, coincided with the traditional "month without gods", believed a period when all of the gods gather in a secret temple. Taking advantage of the absence of Kashima, the coward Namazu causes destruction and sorrows in the human world (image in public domain).
Fig.4. A picture by the Japanese artist Kadzusa-ya Iwaz of 1842 lampooning the myth of Namazu: a Tanuki (a sort of mythical raccoon-dog with the ability to enlarge voluntarily parts of his body) is subduing the catfish with his giant scrotum (figure from Kuniyoshi Project; Copyright 2006 - 2011 William Pearl, non - commercial use granted).
There exist also other versions of the myth, in some stories Kashima doesn't use a rock, but a sword to nail the Namazu onto the ground. According to another version it is the god Kadori controlling the catfish, using a giant pumpkin. Also the main villain can be represented by a giant eel - Jinshin-Uwo - or the giant dragon-beetle Jinshin-Mushi.
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