Japan Meteorological Agency Seismic Intensity Scale

The JMA operates a network of 180 Seismograph s and 600 Seismic Intensity Meter s and provides real-time earthquake reports to the media and on the internet (Japanese page) .

JMA scale explanation

The JMA Scale runs from 0 to 7, with 7 being the strongest. Sometimes Roman Numeral s 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 Meter s 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

(Note: 1 Gal = 0.01 m/s² = 1/980 G )

SEE ALSO

Other Seismic Scales

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Japan Meteorological Agency Seismic Intensity Scale