A scale that grows by powers of ten
Each whole-number increase means about ten times the recorded ground motion and roughly 32 times the energy released.
M 51×Reference
M 632×More energy
M 7~1,000×More energy
Approximate energy released, relative to a magnitude 5 earthquake.
What each range usually means
Effects depend on distance, depth, local ground conditions, and buildings. Use these ranges as a general guide.
| Magnitude | Typical effects |
|---|---|
| 2.5 or less | Usually not felt; recorded by seismographs. |
| 2.5 to 5.4 | Often felt, with minor damage at most. |
| 5.5 to 6.0 | Can cause slight damage to buildings and structures. |
| 6.1 to 6.9 | May cause substantial damage in populated areas. |
| 7.0 to 7.9 | Major earthquake; serious damage is possible. |
| 8.0 or more | Great earthquake; severe destruction near the epicenter. |
Why depth matters
Shaking loses energy as it travels to the surface. A shallow earthquake can produce stronger surface shaking than a deeper earthquake of the same magnitude.
Shallow0 to 70 km
Intermediate70 to 300 km
Deep300 to 700 km
Why two numbers can disagree
Initial magnitudes can change as more stations report. Different measurement methods can also produce slightly different values.