Question

Compare S (secondary) waves and P (primary) waves. Why do they travel at different speeds?

Answer 1

S waves

• These are shear waves .

• The motion of the medium is perpendicular to  direction of propagation of the wave .

• They can propagate only through solids and not through gases or liquids .

• S waves are larger .

• They travel with less speed .

P waves

• These are compression waves .

• These waves produces a force along the direction of propagation .

• They can propagate through solids, gases and liquids.

• P waves are smaller than s waves .

• They travel with 60% greater speed than S waves .

P-waves travel 60% faster than S-waves on average because the interior part of the Earth does not react the same way as the s wave and P wave.