Finding the Epicentre

Triangulation from three stations

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Distance $\approx 8.4$ km per second of S–P lag (crustal speeds).
• One station gives a circle. Three circles pin down the epicentre.
• Early-warning systems use the head start of P-waves.

Steps

1. Distance from the lag
2. Triangulate
3. Distance from a lag
4. Early warning
5. Focus and epicentre
6. A deep quake