EARTHQUAKE

EARTHQUAKErth'kwkEARTHQUAKEThe result of a sudden release of energy in theEarth'scrustthat creates seismic waves.Sudden trembling of the ground caused by the crusts movement.Scientists who study earthquakes -- Seismologists.Scientists say there are over 1 million earthquakes per year or about 1 every second.

How do they occur?Rocks under stress accumulate strain energy over time. When stress exceeds strength of rocks, rock breaks. Strain energy is released as seismic waves. The longer that energy is stored up and is maintained without release, the more likely that a strong earthquake will occur.

Types of seismic waves

1. Body waves - travel through interior 2. Surface waves - travel on surface of earth

Specific Body Waves

Primary or "P" Waves: Primary waves Highest velocity Causes compression and expansion in direction of wave travel.

Secondary or "S" Waves: Secondary or shear waves Slower than P waves but faster than surface waves. Causes shearing of rock perpendicular to direction of wave propagation Cannot travel through liquids Surface Waves"Love" (L) WavesCause vertical & horizontal shakingTravel exclusively along surface of earth

Parts of anEarthquakeCauses of EarthquakesFaulting- Sudden movement of rock along planes of weakness called faults.NORMAL - one side of a fault slips down relative to another REVERSE (& Thrust) - one side of a fault is driven up and over the other STRIKE-SLIP occur where plates meet evenly and slip past each other horizontally. (The angle at which a fault cuts through the earth is referred to as the strike, so a strike-slip fault happens when plates slip along the strike).

Effects of EarthquakesRuptureDeathBuilding collapseFiresLiquefactionLandslides