Outline the features of seismic waves.

Seismic waves are shock waves released by the rupture of rock duing an Earhquake. Seismic waves radiate from the focus of the earthquake and travel through rocks.

Primary waves (P-waves) are compressional waves and therefore vibrate in the direction of travel. P-waves are the fastest seismic waves and reach the Earth's surface first. P-wavs are high frequency and can tavel through the Earths mantle and core.

Secondary waves (S-wavs) vibrate at right angles to the direction of travel and are the second fastest waves, traveing at half the speed of P-waves.

Surface Lowe waves travel near to the Earth's surface and are the slowest waves but cause the most damage.

Raleigh waves occur in complicated, low frequency, rolling motions, spreading out from the earthquake epicentre.

Seimic waves are measued on seismographs an have helped to discover the internal structure of the Earth. This is due to the fact that S-waves can travel through solid mantle but not through the fluid crust and therefore refract upon reaching the core. However, P-waves can tavel through both solid and fluid and can therefore be measured on the opposite side of the epicentre.