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FAQ for Earthquake


7. What is "intensity"?

The intensity of an earthquake is a measure of the degree of vibration that people can feel on the Earth's surface, or the degree of damage for an object under vibration.

Today seismic apparatus is able to portray detailed earthquake acceleration, such that the intensity can be classified according to the information on the acceleration. Scales of the earthquake intensities exist as positive numbers (see Earthquake Intensity Table by the Central Weather Bureau, Ministry of Transportation and Communications).

Earthquake Intensity Table
Central Weather Bureau, Ministry of Transportation and Communications

Seismic Intensity Scale
Intensity Lecel What People Feel Effects Indoors Effects Outdoors
0 Undetectable Imperceptible to humans    
1 Slight People may feel slight shaking when motionless    
2 Weak Most people will feel shaking, and some sleepers may wake up Light shaking of dangling objects such as lamps Stationary vehicles shake slightly, similar to when a truck passes by, but only for a short time
3 Light Almost everyone will feel shaking, and some may experience fear Houses shake; bowls, plates, doors, windows etc. make noise; dangling objects swing Stationary vehicles shake visibly; power lines sway slightly
4 Moderate Will cause a considerable degree of fear; some people will look for shelter, and almost all sleepers will wake up Houses shake violently; objects tumble; heavy furniture moves; slight damage may occur Vehicle drivers feel slight shaking; power lines sway visibly; pedestrians also feel shaking
5 Lower Strong Most people are frightened and panic Some walls crack; heavy furniture may be overturned Vehicle drivers feel obvious shaking; some signboards and chimneys fall or collapse
5 Upper Almost everyone is frightened and panics, and has difficulty walking Large quantities of unsecured items tumble and fall; furniture moves or is overturned; some doors and windows become twisted; some walls crack; a small number of houses with poor seismic resistance may be damaged or collapse Wall tiles fall from some buildings; rockfalls occur in mountainous areas; liquefaction may occur in soft soil; utilities and/or communications may be interrupted in some areas; a small number of brick walls with poor seismic resistance may be damaged or collapse
6 Lower violent Violent shaking makes it difficult to remain standing Some buildings are damaged; heavy furniture is overturned; doors and windows twist Drivers have difficulty driving; soil liquefaction is seen
6 Upper Violent shaking makes it almost impossible to stand Lots of furniture moves violently or is overturned; doors and windows become twisted; some houses with poor seismic resistance may be damaged or collapse, and even houses with better seismic resistance may also be damaged Some ground surfaces crack; landslides may occur in mountainous areas; liquefaction occurs in soft soil; utilities and/or communications may be interrupted on a large scale
7 Extreme Violent shaking make voluntary action impossible Some buildings are seriously damaged or collapse; almost all furniture moves a long distance or tumbles Landslides occur and fissures appear; railroad tracks are twisted; underground pipelines are damaged