Japan Meteorological Agency magnitude 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, MJMA, or M`J`. (These should not be confused with moment magnitudes JMA calculates, which are labeled Mw(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 Mw 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" (in ja). https://kotobank.jp/word/マグニチュード-135837.
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, doi:10.1785/BSSA0860030832, Bibcode: 1996BuSSA..86..832K .
* Bormann, P.; Wendt, S.; Di Giacomo, D. (2013), "Chapter 3: Seismic Sources and Source Parameters", in Bormann, New Manual of Seismological Observatory Practice 2 (NMSOP-2), doi:10.2312/GFZ.NMSOP-2_ch3, http://gfzpublic.gfz-potsdam.de/pubman/item/escidoc:108170:12/component/escidoc:364681/Chapter_3.pdf, retrieved 2021-06-02 .
* Bormann, P.; Saul, J. (2009), Earthquake Magnitude, 3, pp. 2473–2496, http://gfzpublic.gfz-potsdam.de/pubman/item/escidoc:238827:1/component/escidoc:238826/13221.pdf .
* Doi, K. (2010), "Operational Procedures of Contributing Agencies", Bulletin of the International Seismological Centre 47 (7–12): 25, ISSN 2309-236X, ftp://isc-mirror.iris.washington.edu/pub/pdf/bulletin/summary/BulletinSummary20107_pub.pdf . Also available here (sections renumbered).

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