Question

What are the 3 main types of seismic waves? How do they differ from each other?

Answer 1

Hint: The energy and vibration that travels through earth’s layers when an earthquake , volcano or other explosion occurs, is called seismic wave. These waves travel through different layers of earth. As different layers have different densities, these waves get reflected and refracted. Seismographs record the amount of time taken by different waves to reach the surface. They record the frequency and amplitude of seismic waves.

Complete answer: Seismic waves are broadly classified into two categories - body waves and surface waves.
-Body waves are the waves that are generated at the focus of earthquakes. These waves travel in all directions through the body of the earth.
-Body waves are further classified into P waves and S waves.
-P waves or the primary waves are first to arrive at the surface and travel though gaseous, liquid as well as solid material. P waves lead to stretching and squeezing of the material it passes through as it vibrates parallel to the direction of the wave.
-S waves or the secondary waves arrive after P waves and travel only through solid material. S waves travel perpendicular to the direction of the wave and thus it creates troughs and crests in the material that it passes through.
-Surface waves are created when the body waves interact with surface rocks. These are last to reach the surface and are considered to be the one causing the most amount of damage. Surface waves cause displacement of rocks. They are further classified into love waves and rayleigh waves.

Note: P waves are also known as longitudinal waves and S waves are called transverse waves. The seismic waves have helped us understand the interior of earth. Shadow zones help in understanding the same. Shadow zones are basically areas where waves are not reported.