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Earthquakes

Tokyo is near the boundary of three plates, making it an extremely active region for smaller quakes and slippage which frequently affect the urban area with swaying as if in a boat, although epicenters within mainland Tokyo (excluding Tokyo's 2,000 km (1,243 mi) –long island jurisdiction) are quite rare. It is not uncommon in the metro area to have hundreds of these minor quakes (magnitudes 4–6) that can be felt in a single year, something local residents merely brush off but can be a source of anxiety not only for foreign visitors but for Japanese from elsewhere as well. They rarely cause much damage (sometimes a few injuries) as they are either too small or far away as quakes tend to dance around the region. Particularly active are offshore regions and to a lesser extent Chiba and Ibaraki.

Tokyo has been hit by powerful megathrust earthquakes in 1703, 1782, 1812, 1855, 1923, and much more indirectly (with some liquefaction in landfill zones) in 2011; the frequency of direct and large quakes is a relative rarity. The 1923 earthquake, with an estimated magnitude of 7.9, killed more than 100,000 people, the last time the urban area was directly hit.