It’s a tale of culture as much as science: At the time, people attributed earthquakes to Namazu-e, a massive catfish thought to live deep in the Earth. When the fish escaped the control of Kashima, the deity thought to prevent earthquakes, its thrashing shook the planet and triggered catastrophic quakes.
In the wake of the 1855 quake, artists created hundreds of prints depicting the catfish. But another artist left behind something more useful to modern seismologists. Nakamura Nazako III, a Kabuki actor, wrote about how he told women and children to calm down after hearing a strong rumble, then stood up. Afterward, the ground began shaking.
That clue was enough for the researchers to estimate the S-P interval, which helps scientists measure the distance of a location to the center of an earthquake. During an earthquake, different seismic waves arrive at different times. First, fast-moving P (primary) waves arrive, shaking the ground back and forth and often creating a rumbling sound. Then, slower S (shear) waves arrive. Finally, surface waves, which cause the strongest shaking, arrive.
The research “highlights the importance of long-term seismic knowledge,” writes Hornyak.
To learn what the scientists concluded about the earthquake’s center — and read the words of Nakamura Nazako III — look for Hornyak’s engaging article at bit.ly/EdoQuake.