Catalog input
- Number of rows read
- After analysis
- Number of valid events
- After analysis
- Number of events after filtering
- After analysis
- Events at or above Mc (N)
- After analysis
- Detected columns
- After analysis
Filter (optional)
Estimation settings
Results
Cumulative FMD graph
Run an analysis to display the graph.
FMD (Frequency-Magnitude Distribution)
| M | Events | Cumulative (M or greater) | log10(cumulative) |
|---|---|---|---|
| Run an analysis to display FMD rows. | |||
Assumptions and limits
- The b value compares how often small and large earthquakes appear in the selected catalog.
- Set Mc carefully. Different Mc values can change the estimated b and a values a lot.
- Use this tool for learning and exploratory research. Do not rely on it alone for disaster-response decisions.
- The browser processes input data locally and does not send it to the server.
- CSV/TSV line breaks within cells (multi-line cells enclosed in quotation marks) are not supported.
FAQ
What does a large or small b value mean?
A higher b-value means smaller earthquakes make up a larger share of the catalog. Interpretation still depends on data quality and Mc.
How should I choose Mc?
Catalog completeness changes with region, period, and observation network. This calculator does not estimate Mc automatically, so set it from your catalog, literature, or analysis purpose.
Can I use these results for prediction?
Use the results as exploratory evidence only. They are not enough on their own for earthquake forecasts or disaster-response decisions.
What catalog data should I enter first?
Start with earthquake magnitudes from a consistent catalog and set the completeness magnitude Mc before estimating b. Exclude mixed regions or time periods unless you intentionally want a combined sample.
Why can b-value estimates differ between tools?
Different tools may use different Mc choices, magnitude bins, maximum-likelihood formulas, uncertainty estimates, or catalog filters. Align those assumptions before comparing b values.
Earthquake b-value analysis notes
Completeness magnitude matters
The b value is sensitive to Mc. If small events are missing from the catalog, the slope can be biased and the uncertainty will look more precise than it should.
Keep the catalog consistent
Use one region, time window, magnitude scale, and detection network when possible. Mixing catalogs can change the magnitude distribution before the calculation even starts.
Read b with uncertainty
A higher b value generally means relatively more small events; a lower value means relatively more large events. Check uncertainty and sample size before interpreting the difference.
Common mistakes
Do not use aftershock clusters, changing network coverage, or arbitrary Mc values without noting the limitation. Do not compare rounded b values without checking the inputs.
Use limitations
This page supports exploratory Gutenberg-Richter analysis. It does not forecast earthquakes or replace a seismological hazard assessment.
Related tools
- Geology/Environment (Disaster prevention (earthquake/tsunami/ground))
- Moment magnitude Mw (Fault → Mo → Mw)
- P wave/S wave: Initial tremor duration → epicenter distance/occurrence time (for education)
- Earthquake magnitude and energy comparison calculator
- Ground: Simple indicator of liquefaction (for educational use)