A seismograph station can determine its distance from an earthquake's epicenter by _____.

1. subtracting P from S wave arrival time and then determining what that time is equal to in distance
2. mapping P and S wave arrival times on a map
3. subtracting P, S, and L wave arrival times, determining distance from this number, and then mapping it
4. One station can't locate its distance from an epicenter. Three stations must do this.