Question

Everyone knows that an earthquake is the shaking of the ground. Describe the ways in which it acts like a wave. How can the S and P waves be used to determine the location of the epicenter and the nature of the interior of the Earth?

Answer 1

We can locate earthquakes using a simple fact: an earthquake creates different seismic waves (P waves, S waves, etc.) The different waves each travel at different speeds and therefore arrive at a seismic station at different times. P waves travel Fastest, so they arrive first. S waves, which travel at about half the speed of P waves, arrive later. A seismic station close to the earthquake records P waves and S waves in quick succession. With increasing distance from the earthquake the time difference between the arrival of the P waves and the arrival of the S waves increases. This basic approach to locating quakes is illustrated using an example of an earthquake near Mexico.

So,

• Different waves each travel at different speeds and therefore arrive at a seismic station at different times.
• Difference in arrival times between P and S waves can be used to determine the distance between the station and an earthquake epicenter
• By knowing how far away the quake was from three stations we can draw a circle around each station with a radius equal to its distance from the earthquake. The earthquake occurred at the point where all three circles intersect. That is the point of epicenter