Japan Meteorological Agency magnitude scale

Not to be confused with Japan Meteorological Agency seismic intensity scale.

The Japan Meteorological Agency magnitude scale (Japanese: 気象庁マグニチュード) 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 M_w  in the range of 4.5 to 7.5,^[4] but underestimate larger magnitudes.

Notes

1. 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". コトバンク (in Japanese). Retrieved 2021-06-02.{{cite web}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
2. Katsumata 1996; Bormann, Wendt & Di Giacomo 2013, §3.2.4.7, p. 78; Doi 2010.
3. Bormann & Saul 2009, p. 2478.
4. See also figure 3.70 in NMSOP-2.

Sources

• Katsumata, A. (June 1996), "Comparison of magnitudes estimated by the Japan Meteorological Agency with moment magnitudes for intermediate and deep earthquakes.", Bulletin of the Seismological Society of America, 86 (3): 832–842, Bibcode:1996BuSSA..86..832K, doi:10.1785/BSSA0860030832, S2CID 130279928.
• Bormann, P.; Wendt, S.; Di Giacomo, D. (2013), "Chapter 3: Seismic Sources and Source Parameters", in Bormann (ed.), New Manual of Seismological Observatory Practice 2 (NMSOP-2), doi:10.2312/GFZ.NMSOP-2_ch3, archived from the original (PDF) on 2019-08-04, retrieved 2021-06-02.
• Bormann, P.; Saul, J. (2009), "Earthquake Magnitude" (PDF), Encyclopedia of Complexity and Applied Systems Science, vol. 3, pp. 2473–2496.
• Doi, K. (2010), "Operational Procedures of Contributing Agencies" (PDF), Bulletin of the International Seismological Centre, 47 (7–12): 25, ISSN 2309-236X. Also available here (sections renumbered).