Many parts of eastern Japan experienced unusually long and slow shakes on Monday night, following the magnitude 7.5 earthquake that struck off the eastern coast of Aomori Prefecture.

Called ¡°long-period ground motion,¡± this is a lesser-known type of quake that reaches long distances and can be felt especially strongly by people on the upper floors of tall buildings.

After Monday¡¯s quake, wide areas of Hokkaido, Tohoku and parts of the Kanto region including Tokyo, Saitama and Chiba prefectures experienced these shakes, though in varying degrees.