Seismologists study the various types of waves that travel through the Earth's layers following an earthquake. Among these are P waves and S waves, which are crucial for understanding the nature of the seismic event and the structure of the Earth's interior. P waves, or primary waves, are the first to be detected at seismic stations after an earthquake because they travel faster than any other type of seismic wave. These waves are compressional waves, meaning they cause particles in the Earth's material to vibrate back and forth in the same direction as the wave is moving. P waves can travel through all states of the Earth's interior, including solid rock (the crust and mantle) and fluids, such as the outer core. S waves, or secondary waves, follow P waves and are slower. They are shear waves, which means they cause particles to move perpendicular to the direction of the wave's travel. Unlike P waves, S waves cannot travel through liquids, which is why they are absent in the Earth's liquid outer core. Both P and S waves are generated by the sudden release of energy caused by the movement of tectonic plates or other seismic sources. The study of these waves helps scientists to locate the epicenter of an earthquake, determine its depth, and understand the properties of the Earth's layers. read more >>

The first kind of body wave is the P wave or primary wave. This is the fastest kind of seismic wave, and, consequently, the first to 'arrive' at a seismic station. The P wave can move through solid rock and fluids, like water or the liquid layers of the earth.read more >>