Seismic Waves (earthquakes)

Seismic waves are waves produced by sudden energy release inside Earth, especially during earthquakes. They travel through Earth and along its surface.

**Primary waves (P waves)** are longitudinal waves. They are the fastest seismic waves and can travel through: solids; liquids; * gases.

**Secondary waves (S waves)** are transverse waves. They are slower than P waves and travel only through solids.

Surface waves travel along Earth's surface and often produce strong ground motion. They can be particularly damaging near the surface.

The different behaviour of P and S waves provides information about Earth's internal structure. For example, the inability of S waves to travel through liquids helped scientists infer that part of Earth's outer core is liquid.