Earthquake Magnitude Scales Comparison

Interactive visualization showing relationships between different seismic magnitude scales

Richter Scale (ML)

The original magnitude scale developed by Charles Richter in 1935. Measures the amplitude of seismic waves recorded on seismographs. Most accurate for local earthquakes (< 600 km) and magnitudes < 6.5.

Moment Magnitude (Mw)

The most reliable scale for large earthquakes. Based on the seismic moment, which measures the total energy released. Doesn't saturate for large earthquakes and is now the standard for reporting earthquake magnitudes.

Body Wave Magnitude (mb)

Measures short-period P-waves (1 second). Useful for deep earthquakes and nuclear test detection. Tends to saturate around magnitude 6.5-6.8.

Surface Wave Magnitude (Ms)

Based on the amplitude of Rayleigh surface waves with periods near 20 seconds. Good for shallow earthquakes at teleseismic distances. Saturates around magnitude 8.0.

Duration Magnitude (Md)

Based on the total duration of seismic wave coda. Particularly useful for small to moderate earthquakes (M < 5). Easy to calculate and widely used for local earthquake monitoring. Less reliable for larger earthquakes.

JMA Magnitude (MJMA)

Japan Meteorological Agency magnitude based on maximum amplitude. Optimized for Japanese earthquakes and seismic network. Well-calibrated for regional events but shows slight saturation for very large earthquakes.

Body Wave Magnitude Lg (MbLg)

Uses regional Lg waves (guided waves in the crust). Effective for continental earthquakes at regional distances (150-1500 km). Saturates around magnitude 6.5-7.0 due to Lg wave characteristics.

Reference Relationships Used

Moment Magnitude (Mw):
Mw = ML (reference scale, no conversion)
Body Wave Magnitude (mb):
mb = ML for ML < 5.5
mb = 5.5 + 0.7(ML - 5.5) for ML ≥ 5.5
Surface Wave Magnitude (Ms):
Ms = 0.95ML for ML < 5.0
Ms = ML for 5.0 ≤ ML < 7.0
Ms = 7.0 + 0.8(ML - 7.0) for ML ≥ 7.0
Duration Magnitude (Md):
Md = ML + 0.05(ML - 3.0) for ML < 5.0
Md = ML + 0.1 for 5.0 ≤ ML < 6.5
Md = 6.6 + 0.5(ML - 6.5) for ML ≥ 6.5
JMA Magnitude (MJMA):
MJMA = ML - 0.05 for ML < 5.5
MJMA = ML for 5.5 ≤ ML < 7.0
MJMA = 7.0 + 0.85(ML - 7.0) for ML ≥ 7.0
Body Wave Magnitude Lg (MbLg):
MbLg = ML + 0.1 for ML < 5.0
MbLg = ML + 0.05 for 5.0 ≤ ML < 6.0
MbLg = 6.05 + 0.6(ML - 6.0) for ML ≥ 6.0
Sources: Relationships derived from: Bormann et al. (2013) "Magnitude Calibration Formulas" in New Manual of Seismological Observatory Practice (NMSOP-2); Kanamori (1983) "Magnitude scale and quantification of earthquakes"; Utsu (2002) "Relationships between magnitude scales"; IASPEI Working Group on Magnitude (2011). Saturation effects based on empirical observations from global earthquake catalogs.