A seismometer is a device that detects earthquakes. P-waves travel at a known speed between an earthquake and a seismometer. S-waves travel at a slower speed than P-waves. A P-wave and an S-wave from the earthquake arrive at the seismometer at different times. Describe the relationship between the distance from the earthquake to the seismometer and the time between the P-wave and the S-wave arriving.

P-waves and S-waves start at the earthquake's epicentre at the same time. However, P-waves travel faster through the Earth than S-waves. This means that over any given distance, a P-wave will take less time to travel than an S-wave. As the total distance to the seismometer increases, the total travel time for both waves increases. Because of the constant speed difference, the time gap between their arrivals also increases. Therefore, the relationship is that the time difference between the arrival of the P-wave and the S-wave is directly proportional to the distance from the earthquake. A larger time lag means the earthquake was further away.