Japan Meteorological Agency seismic intensity scale

The Japan Meteorological Agency seismic intensity scale is a seismic scale used in Japan and Taiwan to measure the intensity of earthquakes. It is measured in units of shindo (震度^?, seismic intensity, "degree of shaking"). Unlike magnitude measures such as the Moment Magnitude Scale (Mw), and the earlier Richter magnitude scale, which attempt to describe the energy released by the earthquake, the JMA scale describes the degree of shaking at various points on the Earth's surface, and is analogous to the Mercalli intensity scale. The intensity of an earthquake is not totally determined by its magnitude, but varies with event's depth, and distance from the event; for example, a 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 627 seismic intensity meters and provides real-time earthquake reports to the media and on the Internet.

Japan experiences about 400 earthquakes every day, although the vast majority are shindo scale "0" or less and detectable only using specialist apparatus.

The Japan Meteorological Agency (JMA) first assigned a four-stage Shindo in 1884, with the levels: 微 (faint), 弱 (weak), 強 (strong), and 烈 (violent).

In 1898 this scale was changed to a numerical system, assigning earthquakes levels 0–7.

In 1908, the levels on this scale were given descriptions, and earthquakes were assigned levels based on their perceived effect on people. This scale was widely used during the Meiji period, and revised during the Shōwa period with the descriptions seeing an overhaul.

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