Seismologists study the waves generated by earthquakes to understand the nature of the seismic event and the structure of the Earth's interior. When an earthquake occurs, it releases energy that travels through the Earth in the form of waves. The two main types of seismic waves are P waves and S waves. P waves, also known as primary waves, are the fastest moving seismic waves. They are compressional waves that can travel through solids, liquids, and gases. P waves are characterized by their particle motion, which is in the same direction as the wave's propagation. This means that as the wave moves, it compresses and decompresses the material it passes through. S waves, or secondary waves, are slower than P waves and can only travel through solids. They are transverse waves, which means that the particle motion is perpendicular to the direction of the wave's travel. S waves cause the ground to shake side-to-side and up-and-down, which is why they are often more destructive at the surface. read more >>

Energy released during an earthquake travels in the form of waves around the Earth. Two types of seismic wave exist, P- and S-waves. They are different in the way that they travel through the Earth. P-waves (P stands for primary) arrive at the detector first.read more >>