Earthquake Distance Calculator
Estimate earthquake distance from P-wave and S-wave arrival time difference.
Used in basic seismology.
Estimated Distance
Earthquake location can be estimated from the time difference between P-waves and S-waves.
P-waves (Primary waves) travel faster through the Earth. S-waves (Secondary waves) travel slower.
Average wave speeds:
- P-waves: ~6.0 km/s (3.7 mi/s) through Earth’s crust
- S-waves: ~3.5 km/s (2.2 mi/s) through Earth’s crust
Formula:
Distance = Time Difference × (Vp × Vs) / (Vp - Vs)
Where:
- Vp = P-wave velocity (6.0 km/s)
- Vs = S-wave velocity (3.5 km/s)
Example: If S-wave arrives 10 seconds after P-wave:
- Distance = 10 × (6.0 × 3.5) / (6.0 - 3.5)
- Distance = 10 × 21 / 2.5 = 84 km (52 miles)
Quick estimate: Each second of P-S delay ≈ 8 km (5 miles) of distance.
Note: Three or more stations are needed to pinpoint the exact epicenter (triangulation).