Japan Meteorological Agency seismic intensity scale

The Japan Meteorological Agency seismic intensity scale is a measure used in Japan and Taiwan to indicate the strength of earthquakes. It is measured in units of . 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 [ [http://www.seisvol.kishou.go.jp/eq/intens_st/index.html 気象庁 | 震度観測点（全国） ] ] and provides real-time earthquake reports to the media and on the internet. [ [http://www.jma.go.jp/en/quake/ Japan Meteorological Agency | Earthquake Information ] ]

History

Japan experiences approximately 400 [http://www.hinet.bosai.go.jp/about_earthquake/part1.htm Japanese web site; official data of Shindo 1-7 in 1997 to 2006 is 32,244 times, and Shindo 1-3 is 4 to 5 times in a day. Web site of 防災科学技術研究所;National Research Institute for Earth Science and Disaster Prevention=NIED/ Although none of web site is available for basis of 400 times in a day, but 400 times is well told and well assumable number with this data. ] 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.

Following the Great Hanshin earthquake in 1995, "Shindo" was further expanded to a total of 10 levels of earthquake: 0-4, lower/upper 5 （５弱、５強）, lower/upper 6 （６弱、６強） and 7.

The "Shindo" scale has been used in Japan from 1996 without change. [ [http://www.e-pisco.jp/equake/shindo/old/oldshindo2.html 気象庁震度階級（明治17年～昭和23年）] in Japanese] [ [http://wwweprc.eri.u-tokyo.ac.jp/CSS/shindo.html 震度] in Japanese]

JMA scale explanation

The JMA Scale runs from 0 to 7, with 7 being the strongest. The Mercalli intensity scale is sometimes used together with the "Shindo"; however this is not usual practice in Japan. Real-time earthquake reports are calculated automatically from measurements of ground acceleration. The JMA reports the earthquake level based on the ground acceleration, measured automatically with seismic intensity meters. There is no simple and linear relationship between Shindo Number and peak ground acceleration, [ [http://www.jma.go.jp/jma/kishou/know/shindo/keisoku.html Calculation method of seismic intensity (Japanese)] ] ^, [ [http://www.seisvol.kishou.go.jp/eq/kyoshin/kaisetsu/comp.htm Seismic intensity and acceleration (Japanese)] ] so the values of the table below should only be regarded as an approximate orientation.

See also

* Seismic scale
* List of earthquakes

References

External links

* [http://weathernews.jp/quake/ Up dating information of earth earthquakes in Japan in last 7 days] , Japanese language. Circled number is "Shindo"(震度) Number.　Format is Hypocenter of earthquakes, location, north latitude, east longitude and depth.
* [http://www.jma.go.jp/jma/kishou/know/shindo/shindokai.html JMA Seismic Intensity Scale] in both Japanese and English language.