Why is three the minimum number of stations necessary to locate an epicenter?

Answer 1

Three seismic stations are needed to find the epicenter of an earthquake because all three radial circles made by the stations will only meet at one point. (example: if you only had to circles they would meet at two different points)
At least 3

Answer 2

A single seismic station can tell you the distance to an earthquakes epicentre but will give you no information on it's location.

Seismic vibrations take time to travel to a seismic station and when you have two seismic stations you can narrow down the location of the earthquake's epicentre to two possible locations.

Add in a reading from a third station and you can nail down the exact location because if you draw 3 circles one round each station with the size of each circle proportional to the distance of the station form the epicenter, they will intersect at one location on the planet and that location is the epicenter.

Answer 3

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