Japan Meteorological Agency magnitude scale explained

The Japan Meteorological Agency magnitude scale is a seismic magnitude scale set by the Japan Meteorological Agency.^[1]

Overview

In Japan, for shallow (depth < 60 km) earthquakes within 600 km, the Japanese Meteorological Agency calculates^[2] a magnitude labeled MJMA, M_JMA, or M_J. (These should not be confused with moment magnitudes JMA calculates, which are labeled M_w(JMA) or M^(JMA), nor with the Shindo intensity scale.) JMA magnitudes are based (as typical with local scales) on the maximum amplitude of the ground motion; they agree "rather well"^[3] with the seismic moment magnitude in the range of 4.5 to 7.5,^[4] but underestimate larger magnitudes.

Sources

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Notes and References

1. Web site: 第２版,世界大百科事典内言及. 日本大百科全書(ニッポニカ),精選版 日本国語大辞典,ブリタニカ国際大百科事典 小項目事典,知恵蔵,デジタル大辞泉,百科事典マイペディア,世界大百科事典. マグニチュードとは. 2021-06-02. コトバンク. ja.

2. , p. 78; .

3. .
4. See also figure 3.70 in NMSOP-2.