Explanation: There are two types of body waves. They are called P and S-waves. P-waves move faster and are the first to arrive at the surface. These are also called primary waves.

• The P-waves are similar to sound waves. They travel through gaseous, liquid and solid materials. S-waves arrive at the surface with some time lag. These are called secondary waves.
• An important fact about S-waves is that they can travel only through solid materials.
• The earthquake events are scaled either according to the magnitude or intensity of the shock. The magnitude scale is known as the Richter scale.
• The magnitude relates to the energy released during the quake. The magnitude is expressed in numbers, 0-10.
• The intensity scale is named after Mercalli, an Italian seismologist. The intensity scale takes into account the visible damage caused by the event. The range of intensity scale is from 1-12.

Source: NCERT – Fundamental of Physical Geography