Japan Meteorological Agency seismic intensity scale
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The Japan Meteorological Agency seismic intensity scale (気象庁震度階級: Kishōchō shindo kaikyū, or shindo) is a measure used in Japan to indicate the strength of earthquakes. Unlike the Richter magnitude scale (which measures the total magnitude of the earthquake, and represents the size of the earthquake with a single number) the JMA scale describes the degree of shaking at a point on the Earth's surface. As a result, the measure of the earthquake varies from place to place, and a given quake may be described as "shindo 4 in Tokyo, shindo 3 in Yokohama, shindo 2 in Shizuoka".
The JMA operates a network of 180 seismographs and 600 seismic intensity meters and provides real-time earthquake reports to the media and on the internet (Japanese page) (http://www.tenki.jp/qua/quake_0.html).
JMA Scale Explanation
The JMA Scale runs from 0 to 7, with 7 being the strongest. Sometimes roman numerals are used, as in the Mercalli Intensity Scale; however this is not the usual practice in Japan. The real-time reports are calculated automatically from measurements of ground acceleration. The JMA reports the shindo based on the ground acceleration, which can be written in the SI metric units meters per second squared (m/s²).
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 4 m/s²
6+: In many buildings, wall tiles and windowpanes are damaged and fall. Most unreinforced concrete-block walls collapse. 3.15–4.00 m/s²
6−: In some buildings, wall tiles and windowpanes are damaged and fall. 2.50–3.15 m/s²
5+: 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. 1.40–2.50 m/s²
5−: Most people try to escape from danger, some finding it difficult to move. 0.80–1.40 m/s²
4: Many people are frightened. Some people try to escape from danger. Most sleeping people awake. 0.25–0.80 m/s²
3: Felt by most people in the building. Some people are frightened. 0.08–0.25 m/s²
2: Felt by many people in the building. Some sleeping people awake. 0.025–0.08 m/s²
1: Felt by only some people in the building. 0.008–0.025 m/s²
0: Imperceptible to people. Less than 0.008 m/s²