Fast magnitude estimates for classrooms, labs, and fieldwork. Switch scales, validate inputs, and view examples. Save your results in CSV and PDF with ease.
| Scale | Amplitude (μm) | Distance (km) | Seismic moment | Magnitude |
|---|---|---|---|---|
| Local | 12.0 | 80 | — | ~4.90 |
| Local | 35.0 | 150 | — | ~5.55 |
| Mw | — | — | 1.0 × 10^19 N·m | ~6.59 |
Magnitude summarizes earthquake size with a single number that supports fast decisions. Emergency managers use it to anticipate response scale, while engineers use it to compare loads across events. Because the scale is logarithmic, small numerical changes can reflect large physical differences.
Local magnitude estimates start from measured wave amplitude recorded at a station. Larger peak amplitudes typically indicate stronger shaking near the source. In practice, instruments and processing choices affect measured amplitude, so consistent units and careful measurement improve repeatability.
Seismic waves lose energy as they travel. The same earthquake produces smaller amplitudes at greater distances because of geometric spreading and material damping. A distance term corrects for this attenuation, helping measurements from different stations remain comparable.
Moment magnitude (Mw) is based on seismic moment, a physical quantity derived from fault area, slip, and rock rigidity. Mw scales well for very large earthquakes and avoids the saturation that can affect some older amplitude-based scales. Seismic moment is commonly reported in N·m.
On a logarithmic magnitude scale, an increase of one unit corresponds to much larger ground motion and energy release. A widely used approximation relates magnitude to energy using log10(E)=1.5M+4.8, where E is joules. This helps communicate how a 7 can be dramatically more energetic than a 6.
Magnitude alone does not guarantee damage. A “moderate” event near a city can be more disruptive than a stronger event offshore. Depth, local soil, building vulnerability, and rupture direction influence shaking intensity. Use the category label as a quick guide, not a final verdict.
Before calculating, confirm units, ensure values are positive, and avoid mixing distance definitions (epicentral versus hypocentral) without noting the difference. If amplitude is derived from multiple components, be explicit about the chosen peak measure. Keeping a small example table supports validation and training.
This calculator is designed for educational and screening purposes. Professional catalogs may use region-specific corrections, instrument responses, and station networks. For official reporting, rely on a seismic agency’s published magnitude. Still, the calculator is useful for exploring “what-if” scenarios and learning how inputs influence computed values.
Magnitude is a logarithmic indicator of earthquake size, related to recorded wave amplitudes or seismic moment. It helps compare events and estimate relative energy release.
Different scales use different data sources and corrections. Local magnitude uses amplitudes and distance, while Mw uses seismic moment. Mw is preferred for large events because it scales reliably.
Enter amplitude in micrometers and distance in kilometers for the local estimate. Consistent units matter because logarithms amplify unit mistakes.
Enter a positive seismic moment value and select units. If you provide dyne·cm, the calculator converts it to N·m internally before computing Mw.
No. Damage depends on depth, distance to populated areas, ground conditions, and building resilience. Magnitude is one factor among many that control shaking intensity and impacts.
The energy equation gives a rough order-of-magnitude estimate. Real energy partitioning varies by rupture style, stress drop, and regional geology, so treat it as an educational approximation.
Official agencies use calibrated instruments, station networks, and region-specific corrections. This tool uses simplified relationships for learning and quick screening, so differences are expected.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.