Magnitude is not a linear scale
Each extra point multiplies released energy by about 32. A magnitude 6 is not twice a magnitude 3: it releases thirty-two thousand times as much. That is why the decimals in a bulletin genuinely matter.
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Earthquakes near you
Almanaccolo lists recent earthquakes within 300 kilometres of where you are, with magnitude, depth and distance from the epicentre.
How to read it
Depth matters too
A magnitude 4 at five kilometres deep is felt more than a magnitude 5 at two hundred. Depth tells you how much rock sits between the epicentre and the surface: destructive quakes are almost always shallow ones.
What is felt, magnitude by magnitude
| Magnitude | Effect | Frequency worldwide |
|---|---|---|
| < 2 | Not felt | Millions a year, instruments only. |
| 2–3 | Rarely felt | Over a million a year. |
| 3–4 | Felt indoors | Around 100,000 a year. |
| 4–5 | Objects rattle | Around 10,000 a year. |
| 5–6 | Damage to weak buildings | Around 1,500 a year. |
| 6–7 | Serious damage up to 100 km | Around 130 a year. |
| 7+ | Destructive over a wide area | About fifteen a year. |
Data: USGS
Frequently asked questions
What does earthquake magnitude mean?
It measures the energy released. It is not a linear scale: each extra point multiplies energy by about 32, so a magnitude 6 releases thirty-two thousand times more than a magnitude 3.
Why is a deep earthquake felt less?
Because there is more rock between the epicentre and the surface to absorb the energy. A magnitude 4 at five kilometres deep is felt more than a magnitude 5 at two hundred.
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