Mercalli Intensity Calculator
Mercalli shaking level from magnitude.
What it does
Magnitude counts energy while Mercalli counts shaking: one quake releases single energy but rattles each town differently. Near-field bands translate between them roughly.
The tool above takes earthquake magnitude. It returns the MMI level with shaking words and scope.
The default 6.0 reads VII to VIII, very strong to severe, near field. The 4.5 case reads V moderate, and 7.5 reads IX violent.
Earthquake hazard programs publish the I through XII scale with felt descriptions per level. Seismology networks teach magnitude as energy against intensity as experience.
Estimates never replace felt reports or engineering: depth, soils, and buildings rewrite shaking block by block. Report shaking to did you feel it maps after events.
How to use
- Type the magnitude.
- Read MMI first.
- Read shaking words beside it.
- Read the scope last.
- Report real shaking to maps.
- Follow alerts always.
Formula
- M
- Moment magnitude 0 to 10.
- MMI
- Roman numeral shaking level.
USGS earthquake hazards programs publish the Modified Mercalli scale with I through XII shaking descriptions. Seismological network materials mirror intensity as shaking felt versus magnitude as energy released. Bands here estimate near-field shaking; depth, distance, and soils move real reports.
Worked example
Example: magnitude 6 nearby
Default: magnitude 6.0.
- Quake: magnitude 6.0 shallow nearby.
- Band: 6.0 sits VII to VIII.
- Words: very strong to severe shaking.
- Scope: near field; depth and soil shift it.
- Check: far field reads lower always.
- Tool shows VII-VIII, Very strong to severe, Near-field estimate; depth and soil shift it.
Reference table
| Magnitude | MMI | Shaking |
|---|---|---|
| Under 2 | I | Not felt |
| 2 to 3 | II-III | Weak |
| 3 to 4 | IV | Light |
| 4 to 5 | V | Moderate |
| 5 to 6 | VI-VII | Strong |
| 6 to 7 | VII-VIII | Very strong |
| 7 to 8 | IX | Violent |
| 8 plus | X+ | Extreme |
Common mistakes
Try it yourself
Quick checks. Answers sit tucked under each question.
Magnitude 4.5?
V with moderate shaking, near field.
Magnitude 7.5?
IX with violent shaking, near field.
Magnitude 11?
Past 10 exceeds earthly scales: enter 0 to 10.
Questions
MMI scale?
I not felt through XII total destruction, keyed to shaking and damage, not energy.
Magnitude or intensity?
Magnitude measures energy released; intensity measures shaking felt. One quake, many intensities.
Estimate quality?
Near field estimate only: depth, distance, and soils swing real readings.
Real maps?
USGS Did You Feel It maps crowdsource real intensities after events.
Build to math?
No, this screens bands. Alerts and engineers rule safety, never arithmetic.
More than shaking?
Yes, duration, aftershocks, and loose ground all amplify harm beyond one number.