Japan Meteorological Agency magnitude scale

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

Overview

In Japan, for shallow earthquakes within 600 km, the Japan Meteorological Agency calculates a magnitude labeled MJMA, M_JMA, or M_J. or M^{JMA magnitudes are based on the maximum amplitude of the ground motion; they agree "rather well" with the seismic moment magnitude in the range of 4.5 to 7.5, but underestimate larger magnitudes.}