Earthquakes.

By: Laura Barjarow

Chapter 12.

Earthquakes

• A movement or trembling of the ground that is caused by a sudden

release of energy when rocks along a fault move

Seismograph.

• Earthquakes generate seismic waves which can be detected with a sensitive instrument called a seismograph.

• Instrument that records vibrations in the ground

• Seismogram- a tracing of earthquake motion that is recorded by a seismograph.

seismic waves.

• Body waves- in geology, a seismic wave that travels through the body of a medium.

• Surface waves- in geology, a seismic that travels along the surface of a medium and that has a stronger effect near the surface of the medium than it has in the interior.

Body waves.

• P waves- (primary waves, or compression wave); a seismic wave that causes particles of rock to move in a back-and-forth direction parallel to the direction in which the waves traveling; fastest traveling seismic waves and can travel through solids, liquids, and gases.

• S waves- (secondary waves, or shear wave); a seismic wave that causes particles of rock to move in a side-to-side direction perpendicular to the direction in which the wave is traveling; second-fastest seismic waves and can travel only through solids.

Epicenters.

• The point on earth’s surface directly above an earthquakes starting point, of focus.

• Focus- the location within earth along a fault in which the first motion of an earthquake occurs.

Locating epicenters.

How to Locate Epicenter.

• Get three different seismograph reading and plot them on a map. The point which all the circles meet is where the epicenter is.

Elastic Rebound Theory.

• Elastic rebound- the sudden return of elastically deformed rock to its undeformed shape.

• Two blocks of crust push against each other at a fault. Which causes stress but doesn’t move because of friction .

• As stress builds up at the fault, the crust deforms.• The rock fractures and then snaps back into its

original shape, causing an earthquake.

Tsunami’s

• A tsunami is a giant ocean wave that forms after a volcanic eruption, submarine earthquake, or landslide.

• Causes much destruction if it reaches land.