Japan’s Geology

Japan’s Geological History

A History of Disasters

The 2011 Sendai earthquake was a shocking disaster that took thousands of lives and its consequent tsunami caused the most recent nuclear plant meltdown in modern history. However, natural disasters have dotted Japan’s past, and the people of Japan have been adapting for centuries.  Prior to modern science that could explain these geological occurrences, the earthquakes were attributed to a giant catfish god, 鯰 (Namazu). In the Tokugawa Period (1603-1868), Namazu was a general god of disasters and acted more as a mischief-maker and harbinger of disaster. However, after the great Edo Earthquake near the end of the Tokugawa Period, Namazu became more closely correlated with earthquakes themselves. According to folklore, the god 鹿島 (Kashima) was put in charge of guarding Namazu, but the rowdy koi would take any opportunity when Kashima wasn’t paying attention to thrash around violently. In later eras, it was believed that Namazu would do this to punish misbehavior by the human race.

A Tokugawa Era painting depicting Kashima weighing down Namazu with a giant stone. He is also scolding smaller catfish that are supposed to represent great past earthquakes. Photo courtesy of http://historyofgeology.fieldofscience.com/2011/01/namazu-earthshaker.html

More evidence of ancient Japanese people’s experience and adaptation to earthquakes and tsunami include early signs of architectural planning. Large stones have been discovered dating back to 1896 that have inscribed warnings stating, “Remember the calamity of the great tsunamis. Do not build any homes below this point.” The town of Aneyoshi was famously spared from the 2011 tsunami because the town heeded these stones – the flood waters reportedly stopped 300 feet below the stones.

1900 – present

A recent data analysis of major earthquakes in Japan from 1900 to the present has been compiled in an interactive map, shown below, that shows the distribution of epicenters and the magnitude of every earthquake over a 6.5 on the Richter scale. As you can see, there have been hundreds of earthquakes in the past 116 years. One of the worst was the Great Kanto Earthquake on September 1, 1923, which resulted in the greatest loss of life from an earthquake in modern Japanese history. The total death count was over 145,000 people, with most of them attributed to buildings collapsing and crushing people to death as well as a fire tornado that raged through Tokyo.

This is an interactive map via NewScientist, powered by Tableau, that shows all major earthquakes (Magnitude 6.5 or above) that have occurred in Japan from 1900 to the present. Photo taken from Tableau Public

Focusing in on just the earthquakes that resulted in great loss of life since 1900, 12 events pop up. This leads to a frequency of an earthquake resulting in great loss of life once about every 10 years. With a frequency that high, it’s no wonder why Japan has become a world leader in tsunami and earthquake research as well as early warning systems and prevention technology. Japan’s proclivity to these great natural disasters has caused the country much grief, but it has also spurred them to make societal changes to prevent the consequences of residing right over a subduction zone.

All major earthquakes resulting in significant loss of life from 1900 to present. There are 12 total, resulting in a period of about 1/10 years. Photo courtesy of Tableau Public

The most recent major earthquake to hit Japan was the 2011 Sendai Earthquake and the chaos surrounding the Fukushima Nuclear Reactor Meltdown. Footage of the disaster shows just how powerful and devastating a tsunami can be, especially on flat plains.

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