Body waves
Topic: Interior of the Earth: Earthquakes, Volcanoes and the Layered Earth · NCERT: Class 11, Ch 3 "Interior of the Earth"
Meaning
Body waves are seismic waves that start at the focus and travel through the inside, or "body", of the earth in all directions. There are two kinds. P-waves (primary waves) are the fastest. They pass through solids, liquids and gases, and they squeeze and stretch the rock along their direction of travel. S-waves (secondary waves) arrive next. They pass through solids only, and they shake the rock at right angles to their direction of travel. Body waves travel faster in denser material, and they bend or bounce where the material changes. This is how they reveal the earth's layers.
Example
The Bhuj earthquake of 2001 in Gujarat sent body waves through the whole earth. Seismographs around the world recorded the P-waves first and then the S-waves.
Don't confuse with
- Surface waves: these form when body waves reach surface rocks. They travel only along the surface, arrive last and do the most damage.