Although the entire nation is vulnerable to quakes, the possibility of a quake that could wipe out the heavily populated Tokyo area causes the most anxiety. The area between Tokyo and Osaka, called the Tokai region, is a hot zone of seismic activity because it is the spot where the Philippine Sea plate is butting heads with the Eurasian plate. That is before any outbreak of fire. A mega-quake beneath the capital, while long feared, is less likely in the short term, scientists say. Authorities have been on edge since April 20 of this year when a series of thousands of tremors, most not felt without seismic equipment, have rattled the area.
Japan is also vulnerable to tsunami, a large sea wave that originates from a quake.
The largest tsunami to strike the country this century was the 1933 Sanriku tsunami, which killed 3,008 people in northeastern Japan. It sent a sea surge 14 meters high washing over coastlines.