Just like density, the elastic moduli change with pressure and temperature. Pressure tends to increase the modulus, temperature tends to decrease the modulus. A rock's elastic moduli are characteristic of that rock type and are controlled by the rock's mineral content. We can measure a rock's elastic moduli in a laboratory. In elastic material, disturbances that transmit energy called elastic waves .
Seismic waves are elastic waves that travel through Earth.
Surface Waves P waves travel fastest and thus are the first waves to arrive. They are sound waves that travel through Earth. They travel slower than P waves but are usually larger than P waves. Surface waves travel along Earth's surface and are the largest waves observed at distance from shallow earthquakes. P waves transmit a strain that squeezes or expands a rock in the direction that the wave is moving.