The Japanese archipelago is located in an area where several continental and oceanic plates meet. This is the cause of frequent earthquakes and the presence of many volcanoes and hot springs across Japan. If earthquakes occur below or close to the ocean, they may trigger tidal waves (tsunami).
In the last one hundred years, there have been over 30 earthquakes of magnitude 7.0 or above.
In 1854-55, the years of the Great Ansei earthquakes, there were 120 earthquakes and tremors in the Edo (Tokyo) region, with 20,000+ casualties.
The Mino-Owari earthquake of October 1891 is the largest known inland earthquake in Japan, with casualties of over 7000.
The Meiji-Sanriku earthquake of June, 1896 occurred off the coast of Sanriku in Iwate Prefecture, causing a tsunami of 25 m (82 ft) 35 minutes after the quake which destroyed hundreds of houses and killed over 27,000 people.
The Great Kanto Earthquake, the worst in Japanese history, hit the Kanto plain around Tokyo in 1923 and resulted in the deaths of over 100,000 people. It devastated Tokyo, the port city of Yokohama, surrounding prefectures of Chiba, Kanagawa, and Shizuoka. An index of the power of this earthquake was the fact that the 93-ton Great Buddha statue at Kamakura slid forward almost two feet. Manly Hall visited Japan just after this earthquake.