How do you calculate the distance from an earthquake?

The distance from an earthquake epicenter can be calculated using the time difference between the arrival of P-waves and S-waves at a seismograph station. By measuring this time lag and using the known velocity of seismic waves through the Earth's interior, the distance can be estimated. The greater the time lag between the arrival of the P-wave and S-wave, the farther the seismograph station is from the earthquake epicenter.