Earthquakes produce seismic waves, which travel through Earth. Primary waves, or P-waves, are longitudinal. They can travel through both solids and liquids. Secondary waves, or S-waves, are transverse. They can travel through solids only. P-waves travel at approximately 8.0 km/s, and S-waves travel at approximately 4.5 km/s. Following an earthquake, vibrations are recorded at seismological stations around the world.
(a) Calculate how long P-waves and S-waves take to travel from an earthquake to a seismological station that is 2.4 X 10^3 km away. Express your answers in minutes.
(b) Why do you think that transverse waves are called secondary waves?
(c) By referring to Figure 3, explain how observing P-waves and S-waves helps geophysicists analyze the structure of Earth's interior.