Chapter 8 Section 1

Earthquakes:• Vibration of Earth created when there is a rapid release of energy• Caused by slippage along a fault• Faults are fractures in Earth where movement has occurred

Tension forces

Compression forces

Shearing forces

• Focus – point where an earthquake begins

• Epicenter – point on the surface above the focus

• Seismic waves – any energy waves made by an earthquake

• 1300 Km long

• Displacement can occur 100-200 km at a time

• Some sections move slowly

• Some sections lock for hundreds of years and then break

Views of the San Andreas Fault

The Cause of Earthquakes:• Rapid release of energy

• Forces in the Earth deform rock – stores elastic energy - suddenly breaks

• Energy released as seismic waves

• Elastic rebound – the tendency for a rock to spring back after an earthquake

• Aftershocks – earthquake that occurs soon after a major earthquake

• Foreshock – small earthquakes occurring before a major earthquake