Seismic Magnitude Converter

Earthquake magnitude is logarithmic: the underlying Gutenberg-Richter relation used here means each whole-number increase in Magnitude corresponds to roughly 31.6 times more Energy Released, not a proportional or doubled increase. So the jump from magnitude 6 to 7 releases about as much extra energy as the jump from 5 to 6 and from 4 to 5 combined, which is why moderate and major earthquakes differ so dramatically in destructive potential despite a "small" difference in the number itself.

This calculator clamps MMI between 1 and 12 because that's the full range of the Modified Mercalli Intensity scale itself -- 12 represents total destruction, so there's no higher category to report even as Magnitude and Energy Released keep climbing. In practice this ceiling is reached well within the calculator's own Magnitude range, which is why very large magnitude values show the same MMI reading despite representing very different amounts of released energy.

No. The Magnitude Scale selector only changes the label shown next to your result (Scale) -- it does not change Energy Released, TNT Equivalent, or MMI, which are all computed from the numeric Magnitude value alone regardless of which scale you select. This reflects that Richter and Moment Magnitude are designed to report comparable numbers for most earthquakes, even though they're derived from different underlying measurements.

Energy Ratio vs M4.0 divides your earthquake's Energy Released by the energy of a reference magnitude-4.0 event, giving you a quick multiplier for how much bigger the shock is in raw energy terms. Because the underlying relationship is logarithmic, this ratio grows extremely fast with Magnitude -- a magnitude 7.0 earthquake releases on the order of tens of thousands of times more energy than a magnitude 4.0 event (about 31,600 times, following the same ~31.6x-per-whole-number relationship described above).

Approx. Global/Year is a rough estimate of how many earthquakes at or above your entered Magnitude occur worldwide in a typical year, based on published long-term earthquake-frequency statistics (for example, roughly one magnitude 8+ event and roughly fifteen magnitude 7+ events globally per year). It's a frequency estimate, not a measure of energy or intensity -- it doesn't come from the Gutenberg-Richter energy relation used for Energy Released, and it should be read as a long-run global average rather than a prediction for any specific year or location.