Question

When earthquakes occur, seismic waves are sent through the Earth. The two most common types of seismic waves are P waves and S waves. The graph below shows how P waves and S waves can travel through Earth.


Modified from image courtesy of USGS

Based on the graph, what is true about P waves and S waves?
A.
They both travel slower than 1,000 miles per hour.
B.
They travel at different speeds through the Earth.
C.
They both travel faster than 7,000 miles per minute.
D.
They travel at the same speed through the Earth.

Answer 1

B. They travel at different speeds through the Earth.

Explanation: P waves arrive earlier (reach a given distance in less time) than S waves, so P waves travel faster. The difference in arrival times on the graph shows the two wave types move at different speeds.