Earthquakes

Causes of Earthquakes An earthquake is a shaking of the Earth’s crust cause by a release of energy. Earthquakes happen because – eruption of a volcano, collapse of a cavern, impact of a meteor Most major earthquakes are caused by the movement of two faults (Fault  a break in the lithosphere {crust} between two lithospheric plates)

Focus …… The point where the first movement occurs

Epicenter….. The point on Earth’s surface directly above the focus

Waves Body waves  waves that travel from the focus of the earthquake through the Earth

P-waves P waves  primary waves, compressional waves  squeeze and stretch rock materials as they pass through Earth; p-waves can travel through any material….solid rock, magma, ocean water, air

S-Waves S waves  secondary waves, shear waves  cause particles of rock material to move at right angles to the direction in which the waves are traveling; s-waves can ONLY travel through solid material, NOT liquids or gases

Surface Waves Earthquake waves that travel along Earth’s surface. Love waves  cause particles of material to move from side to side, in a direction PERPENDICULAR to the waves’ direction of travel Rayleigh waves  travel slower than Love waves; material moves in a elliptical pattern

Seismograph

Seismograph Detects and records waves produced by earthquakes

Magnitude Strength of an earthquake Charles Richter (1935)  Richter Scale ; each level on the scale is 31 times greater than the level before it

Earthquake Hazards…… Ground shaking and foundation failure (buildings falling over, completely collapsing) Liquefaction  loose soil that moves like a liquid instead of a solid http://www.youtube.com/watch?v=j0sLyJpfTE8 Aftershocks  smaller earthquakes that follow after the main earthquake http://www.youtube.com/watch?v=Z7eABGpOHv8 Fire http://www.youtube.com/watch?v=f5xt8oQTApE Tsunami  underwater earthquakes that create huge ocean waves http://www.youtube.com/watch?v=k8IAgUNr6x4