Japan Meteorological Agency magnitude scale
# 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.

## Overview

In Japan, for shallow (depth < 60 km) earthquakes within 600 km, the Japanese Meteorological Agency 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; they agree "rather well" with the seismic moment magnitude $M_w$  in the range of 4.5 to 7.5, but underestimate larger magnitudes.

