The Japan Meteorological Agency magnitude scale () is a seismic magnitude scale set by the

Japan Meteorological Agency The Japan Meteorological Agency (JMA; ''気象庁, Kishō-chō'') is a division of the Ministry of Land, Infrastructure, Transport and Tourism dedicated to the Scientific, scientific observation and research of natural phenomena. Headquartered ...

Overview

In Japan, for shallow (depth < 60 km) earthquakes within 600 km, the Japan Meteorological Agency (JMA) calculates 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 Ground motion is the movement of the Earth’s surface from earthquakes or explosions. Ground motion is produced by seismic waves that are generated by sudden slip on a fault or sudden pressure at the explosive source and travel through the Eart ...

; they agree "rather well" with the seismic moment magnitude in the range of 4.5 to 7.5,See also figure 3.70 in NMSOP-2. but underestimate larger magnitudes.

Notes

Sources

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(sections renumbered). Seismic magnitude scales Japan Meteorological Agency {{Seismology-stub