The SP timing method is a technique, which is useful for finding the epicenter of the earthquake. The Seismograph at a particular station shows the S and the P waves. The difference between the S and the P waves can be used to determine the distance, which waves have travelled in order to reach the seismic station.
The distance obtained is the distance of the epicenter from that seismic station, in order to determine the epicenter the circle is drawn in the map keeping the seismic center at the center. Same process is done by three or more seismic centers. The point, where the circle drawn by three or more seismic centers meet is considered as the epicenter.
Hence, the correct answer is Three.
