What Causes Earthquakes? As Earth’s plates scrape against each other, stress builds up along faults. A fault is a break in the Earth’s crust.

Earthquakes Focus: Where earthquake starts Epicenter: Spot on the surface directly over the focus

Earthquake waves All Earthquakes give off energy in the form of waves. Earthquake waves are called seismic waves Two types of seismicwaves P Waves S Waves

Earthquake waves (Seismic waves) Longitudinal waves are called Primary waves (p-waves) They move faster than secondary waves Transverse waves are called secondary waves (s-waves) They move more slowly than p-waves

Waves Longitudinal waves Matter in the medium moves back and forth along the same direction that the wave travels.

Seismic Waves Transverse waves Particles in the medium moves at right angles to the direction of the wave.