The Richter scale, explained
Earthquake magnitude is logarithmic: each step means about 32 times more energy. Slide through the scale to feel how fast it grows.
- Energy released
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- Compared with one step lower
- About 32 times the energy, 10 times the shaking amplitude
- What you would feel
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- How often, worldwide
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- A real one
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From barely recorded to world-changing
Compare two earthquakes
Richter, moment magnitude and intensity
Charles Richter created his scale in 1935 for Southern California. It saturates for very large quakes, so seismologists now mostly report the moment magnitude (Mw), built to match Richter's numbers but measured from the size of the fault slip. News still says "Richter scale" for both.
Magnitude is one number per earthquake: its size at the source. Intensity (the Modified Mercalli scale, I to XII) is how strong the shaking is at a given place, which depends on distance, depth and ground.
Because the scale is logarithmic, a magnitude 7 releases about 1,000 times the energy of a magnitude 5, and the 2011 Japan earthquake (9.1) about 32,000 times that of a 6.1.