Japan Meterological Agency seismic intensity scale
The Japan Meterological Agency seismic intensity scale is used in Japan to measure the strength of earthquakes. Unlike the Richter scale (which measures the total magnitude of the earthquake) the JMA scale describes the degree of shaking at a point on the Earth's surface, so the size of the earthquake may be described as "4 JMA in Tōkyō".
The JMA operates a network of 180 seismographs and 600 roman numerals are used, however this is not the usual practice in Japan. The real-time reports are calculated automatically from measurments of ground acceleration. (Note: 1 gal = 0.01 m/s² = 1/980 g)
7 - In most buildings, wall tiles and windowpanes are damaged and fall. In some cases, reinforced concrete-block walls collapse. Peak ground acceleration greater than 400 gal
6 upper - In many buildings, wall tiles and windowpanes are damaged and fall. Most unreinforced concrete-block walls collapse. 315 -- 400 gal
6 lower - In some buildings, wall tiles and windowpanes are damaged and fall. 250 -- 315 gal
5 upper - In many cases, unreinforced concrete-block walls collapse and tombstones overturn. Many automobiles stop due to difficulty in driving. Occasionally, poorly installed vending machines fall. 140 -- 250 gal
5 lower - Most people try to escape from danger, some finding it difficult to move. 80 -- 140 gal
4 - Many people are frightened. Some people try to escape from danger. Most sleeping people awake. 25 -- 80 gal
3 - Felt by most people in the building. Some people are frightened. 8 -- 25 gal
2 - Felt by many people in the building. Some sleeping people awake. 2.5 -- 8 gal
1 - Felt by only some people in the building. 0.8 -- 2.5 gal
0 - Imperceptible to people. Less than 0.8 gal
- See also:Mercalli Intensity Scale
