Earthquake Calculator Guide: Magnitude, Energy, Distance, and Shaking
Use earthquake math carefully: compare magnitude energy, estimate distance from P-S delay, and model simplified shaking intensity with clear limits.
The Calculator Has Three Separate Earthquake Modes
The Do The Calculation earthquake tool is not one single earthquake answer. It has three educational modes: magnitude-to-energy comparison, epicenter distance from P-S wave delay, and a simplified ground-shaking estimate. Keep those modes separate. Energy describes the source event, distance uses wave arrival timing, and intensity describes local shaking at a site.
Pick the right earthquake calculation
Each mode answers a different scientific question.
Energy mode
Enter one magnitude, or compare two magnitudes, to estimate joules, TNT equivalent, and ratios.
Distance mode
Enter S-minus-P delay and wave velocities to estimate station distance from the source.
Intensity mode
Enter magnitude, distance, soil type, and depth to estimate simplified PGA and MMI class.
Interpret limits
Use results for learning and scenario comparison, not emergency decisions or prediction.
Magnitude and Energy: Why One Whole Number Matters
The energy mode uses the common logarithmic relationship E = 10^(1.5M + 4.8), with E in joules. That means each one-unit magnitude increase multiplies estimated energy by about 31.6 and wave amplitude by 10 when two magnitudes are compared. This is why a magnitude 6 is not just slightly larger than a magnitude 5.
Swipe sideways to compare columns.
| Metric | Calculator output |
|---|---|
| Magnitude being evaluated | 6.0 |
| Comparison magnitude | 5.0 |
| Energy | 63,095,734,448,019 J |
| TNT equivalent | 15,080.24 tons |
| Energy ratio | 31.62x |
| Amplitude ratio | 10x |
A one-magnitude increase is not linear
The calculator returns the same ratios for 6 vs 5 and 7 vs 6.
Amplitude ratio
One magnitude step
Energy ratio
One magnitude step
Distance from P-S Delay
P waves usually arrive before S waves. The calculator estimates distance from the time gap between those arrivals using the selected P-wave and S-wave velocities. With the default 6.0 km/s P-wave velocity and 3.5 km/s S-wave velocity, a 10-second S-minus-P delay returns an 84 km distance estimate.
Swipe sideways to compare columns.
| Input or result | Value |
|---|---|
| P-S delay | 10 seconds |
| P-wave velocity | 6.0 km/s |
| S-wave velocity | 3.5 km/s |
| Estimated distance | 84.0 km |
| P travel time | 14.0 seconds |
| S travel time | 24.0 seconds |
Shaking Intensity Is Site-Specific
The intensity mode estimates simplified peak ground acceleration from magnitude, distance, focal depth, and soil type. It then maps PGA thresholds to a Modified Mercalli-style class. This is a teaching model. Real ground motion depends on fault geometry, rupture direction, basin effects, building type, local geology, and recorded waveform data.
Swipe sideways to compare columns.
| Metric | Calculator output |
|---|---|
| PGA | 1.38%g |
| MMI class | IV |
| Shaking label | Light |
| Damage label | None |
Magnitude, distance, and intensity are different
Do not mix the meaning of these outputs.
Magnitude
Describes event size and energy release.
Distance
Describes how far a station is from the source estimate.
Intensity
Describes local shaking effects at a specific place.
Safety Limits and Prediction Limits
This calculator is for education, scenario comparison, and understanding earthquake math. It cannot predict earthquakes. USGS states that scientists cannot predict the exact date, time, location, and magnitude of a future major earthquake. For preparedness, alerts, and hazard decisions, use official geological and emergency-management sources.
Open the Earthquake Magnitude & Energy CalculatorCompare earthquake energy, estimate P-S delay distance, and explore simplified shaking intensity scenarios.Official Sources Checked
- USGS earthquake prediction FAQ: https://www.usgs.gov/faqs/can-you-predict-earthquakes
- USGS earthquake travel times: https://www.usgs.gov/programs/earthquake-hazards/earthquake-travel-times
- USGS P-wave and S-wave paths: https://www.usgs.gov/media/images/p-wave-and-s-wave-paths-through-earth
Earthquake Calculator FAQ
Can this calculator predict earthquakes?
No. It models educational scenarios after you enter assumptions; it cannot predict future earthquakes.
Why does one magnitude step matter so much?
The calculator uses a logarithmic relationship, so one magnitude unit means about 10x amplitude and 31.6x energy.
What is the energy formula?
Energy in joules equals 10 raised to the power of 1.5 times magnitude plus 4.8.
What does P-S delay mean?
It is the time difference between the first P-wave arrival and the S-wave arrival at a station.
Why must P-wave velocity be greater than S-wave velocity?
The distance formula depends on P waves arriving first; if the velocity order is invalid, the calculator returns zero distance.
What is PGA?
PGA means peak ground acceleration, reported here as a percentage of gravity.
What does MMI mean?
MMI refers to Modified Mercalli-style intensity classes describing local shaking effects.
Does soil type affect shaking?
Yes. The simplified model adds a soil factor for stiff and soft soil, which increases estimated PGA.
Why can the same earthquake feel different in different places?
Distance, depth, soil, structures, basin effects, and rupture direction can all change local shaking.
Should I use this for safety decisions?
No. Use official alerts, hazard maps, emergency guidance, and professional engineering or seismology resources.
Written by
Do The Calculation Team
Do The Calculation Editorial Board
The Do The Calculation Editorial Board is comprised of software engineers, finance analysts, and technical contributors focused on building clean, accurate, and easy-to-use calculator tools.