The Nankai Trough and Earthquakes
The Nankai Trough is an ocean-floor trench that runs along the Pacific coast of Japan, where the Eurasian and Philippine Sea plates intersect. Powerful earthquakes occur here periodically, often causing large tsunamis. The people of southern Shikoku have always been exposed to this threat, which has forced them to adapt in various ways. The numerous stone monuments that dot the city of Tosashimizu are one example of this. Many of these memorials were inscribed with details such as the height of past tsunamis and how far inland the waves reached, so that future generations would know to be prepared. As the Japanese government estimates a high probability that a Nankai Trough megathrust quake will occur within the coming decades, preparedness is certainly in order. Nankai Trough earthquakes, however, can be thought of as more than just a danger. Sustained tectonic activity along the trench over hundreds of thousands of years has significantly shaped the landscape around Tosashimizu, helping to bring about the region’s steep cliffs, numerous bays, and abundant fishing waters.