Question

How can seismic waves be used to determine an earthquakes epicenter????

Answer 1

Tectonic plates sliding apart can cause aftershock.

Answer 2

The difference in arrival time between the two types of seismic wave can be used to calculate the distance of the earthquake's epicenter from the seismometer, as the further away an earthquake is, the greater the lag time between the detection of the S waves relative to the P waves.