Earthquake Energy Calculator

Magnitude

Compare with magnitude

Result

Times the energy31.62
Times the amplitude10
TNT equivalent, t15,080.24
In Hiroshima bombs1.002
Energy, J63,095,734,448,019
What happensbuilding damage for tens of kilometres

One point on the scale is thirty-two times the energy

Calculates the energy released by an earthquake in joules and TNT equivalent and how many times stronger one magnitude is than another.

Magnitude is logarithmic, and it is logarithmic twice over. One whole point is ten times the wave amplitude a seismograph draws — but about thirty-two times the energy released, because energy scales as ten to the power of one and a half.

That is why the difference between a magnitude 6 and a magnitude 8 is not a third worse but a thousand times the energy. Two points is 31.6 squared.

What this calculator shows

The energy in joules and in tonnes of TNT
How many times the energy and the amplitude exceed the magnitude you compare against
The energy in Hiroshima-bomb units and what happens at that magnitude

What to keep in mind

The Gutenberg–Richter relation is used: the base-ten logarithm of the energy in joules equals 1.5 times the magnitude plus 4.8.
This is the energy released at the source. Damage also depends on depth, distance, ground conditions and building stock, none of which is in the magnitude.

FAQs

Is a magnitude 7 ten times a magnitude 6?

In wave amplitude yes; in energy it is about 32 times. Both statements are correct, which is why the comparison is so often reported wrongly.

What is the difference between magnitude and intensity?

Magnitude describes the event and there is one number for it. Intensity describes the shaking at a place, and one earthquake has many intensities depending on where you stood.

Why does the scale stop near ten?

Because magnitude depends on the length of fault that ruptures, and the earth has no faults long enough to go much beyond 9.5 — the value of the 1960 Chile earthquake, the largest ever recorded.

Is the Richter scale still used?

Not for large events. The moment magnitude scale replaced it because the Richter scale saturates above about 7, but the numbers are close enough that the name stuck in the press.

Worked example

A magnitude six

Input: magnitude 6 against magnitude 5

Output: 31.6 times the energy

Note: That is 6.3 × 10¹³ joules, or about 15 kilotonnes of TNT — roughly one Hiroshima bomb, released tens of kilometres underground.

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Result

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