Earthquake Energy Calculator
Released energy, TNT tons, and Hiroshima equivalents from magnitude.
What it does
Earthquake energy explodes with magnitude: each whole unit multiplies released energy near 28 times here (32 by the classic form), so a 7 carries roughly 750 times a 5. Joules turn into TNT tons and Hiroshima units to make the scale graspable.
The tool above takes moment magnitude. It returns energy with TNT equivalent and Hiroshima count beside them.
The default magnitude 7 gives 2.09 PJ (499.35 kilotons, 33.3 Hiroshimas). A 5 gives 2.75 TJ (658 tons), while a 9.1 gives 2.21 EJ (527.73 megatons).
The relation follows geological survey magnitude science with published energy studies matching the form. Both use log energy near 5.24 plus 1.44 times magnitude, noting forms vary slightly.
How to use
- Enter the moment magnitude Mw.
- Read energy first in scaled joules.
- Read TNT tons for the explosive picture.
- Read Hiroshimas for the human scale.
- Remember shaking damage follows more than energy.
Formula
- 1.44
- Slope: each unit multiplies energy near 28x.
- 4.184e9
- Joules per ton of TNT.
- 15 kt
- Hiroshima reference yield used here.
Rough estimate: published energy forms vary slightly around these constants. Magnitude measures size at the source; shaking and damage depend on depth, distance, and ground.
Worked example
Example: magnitude 7
Default: magnitude 7.
- Exponent: 5.24 + 1.44 x 7 = 15.32.
- Energy: 10^15.32 = 2.09 PJ.
- TNT: 2.09e15 / 4.184e9 = 499.35 kilotons.
- Hiroshimas: 2.09e15 / 6.276e13 = 33.3.
- Tool shows 2.09 PJ, 499.35 kilotons of TNT, 33.3 Hiroshimas (15 kt each).
Reference table
| Magnitude | Energy | TNT |
|---|---|---|
| 5.0 | 2.75 TJ | 658 tons of TNT |
| 7.0 | 2.09 PJ | 499.35 kilotons of TNT |
| 9.1 | 2.21 EJ | 527.73 megatons of TNT |
Limits
- Rough estimate; published forms vary slightly.
- Energy is not damage: depth and distance rule shaking.
- Single number hides rupture complexity.
- Tsunami needs water displacement, not just energy.
Common mistakes
- Reading magnitude as linear: 8 is not twice 4.
- Confusing amplitude 10x with energy 28x.
- Mixing Richter with moment magnitude casually.
- Equating TNT tons with damage tons.
- Forgetting depth in shaking estimates.
Try it yourself
Quick checks. Answers sit tucked under each question.
Magnitude 5?
2.75 TJ: 658 tons of TNT, 0.044 Hiroshimas.
One unit more means?
Near 28 times the energy here: 10^1.44 is 27.5 (32 classic).
Magnitude 9.1?
2.21 EJ: 527.73 megatons, 35.2 thousand Hiroshimas.
Questions
How much energy is a magnitude 7?
About 2.09 PJ: 499 kilotons of TNT, 33 Hiroshimas.
What does each unit add?
Near 28 times more energy here (amplitude grows 10 times).
Richter or moment magnitude?
Modern science uses moment magnitude Mw; Richter saturates on big ones.
Energy versus damage?
Depth, distance, buildings, and soil decide damage more than joules.
Biggest ever?
Chile 1960 at 9.5: thousands of megatons by this math.
Why do forms differ?
Energy integrates the whole rupture; authors fit slightly different constants.
Sources
- USGS: Earthquake magnitude, energy release, and shaking
- Annals of Geophysics: Magnitude and energy of earthquakes (Gutenberg-Richter)