Earthquake Epicenter

Use seismic wave data to triangulate earthquake locations

Earthquakes generate two main types of body waves. P-waves (primary, compressional) travel fastest — about 6 km/s through Earth's crust — and arrive at seismic stations first. S-waves (secondary, shear) travel slower — about 3.5 km/s — and arrive after. The farther you are from the earthquake, the bigger the time gap between P and S arrivals. By measuring this time delay at a single station, you can calculate the distance to the epicenter, but not the direction. With two stations you narrow it to two possible points. With three or more stations, you can pinpoint the exact location — this is triangulation. Each station draws a circle on the map with radius equal to its calculated distance. The unique point where all circles intersect is the epicenter. Real seismological networks use hundreds of stations and computers to locate earthquakes within seconds. Earthquake depth (shallow vs. deep) also affects wave behavior and damage patterns — shallow quakes under 70 km cause the most surface damage.