Two ways to estimate distance
The S-P wave method uses the delay between faster P waves and slower S waves. The coordinate method uses latitude and longitude to estimate the surface distance between two points.
When to use this calculator
Use this page for classroom exercises, quick earthquake context or understanding how epicenter distance is estimated. It is not an official earthquake alert or hazard product.
What this does not do
This calculator does not predict damage, shaking intensity, aftershocks, building safety or earthquake probability. Check official geological and emergency sources for real events.
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FAQ
What is S-P time?
It is the difference between the arrival time of S waves and P waves on a seismogram.
Is the S-P distance exact?
No. It is a simplified estimate.
Can this locate an epicenter?
A single distance does not locate an epicenter. Triangulation requires distances from multiple stations.