# Earthquakes The movement of the ground, caused by waves from energy released as rocks move along faults.

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Earthquakes The movement of the ground, caused by waves from energy released as rocks move along faults.

Faults Rocks break and move along surfaces called faults.
When the elastic limits of rock is pass an earthquake results. Normal Faults Reverse Faults Strike-slip Faults

Normal Faults Tension forces
rock above the fault (head wall) moves down in relation to the rock below the fault surface (foot wall).

Reverse Faults Compression Forces
The rocks above the fault surface (head wall) moves up and over the rock below the fault surface (foot wall).

Strike-slip Fault Shear Forces also called a transform fault
rock on either side of the fault surface move past each other.

Seismic Waves In an earthquake, the energy waves that move outward from the earthquake focus and make the ground quake. Primary wave (P wave) Secondary wave (S wave) Surface wave (Love wave)

Primary Wave Moves within the ground, outward from the focus.
Causes rock to move back and forth in the direction of the wave. Fastest of the waves. Arriving at a seismic station first.

Secondary Wave Moves within the ground, outward from the focus.
Causes rock to move at right angles to the direction of the wave. Arrives at the seismic station second.

Surface Waves Travel on the surface of the ground, outward from the epicenter. Moving particles in an elliptical motion as well as back-and-forth swaying motion. Are the slowest of waves. Are the most destructive of wave.

Epicenter vs.. Focus Focus: the point in Earth’s interior where energy release occurs. Epicenter: The point on Earth’s surface directly above the earthquake’s focus.

Locating the Epicenter
Three seismic stations are needed. Record the difference in time of the arrival of the P and S waves. (using a seismograph) Using a chart, the difference in time will tell how far the earthquake epicenter is away from the station. Triangulation of three stations gives the location.

The Inner Core and Seismic Waves
S waves will not pass through the liquid outer core of the Earth. P waves are deflected as they enter the outer part of the inner core creating a shadow zone on the earth surface.

Richter Scale Measures the energy release from an earthquake.
Measured in magnitude, the greater the magnitude the greater the damage. A 1.0 increase of magnitude equals 32 times as much energy!

Tsunamis Also known as a tidal wave (has nothing to do with tide!!)
Seismic sea wave can travel thousands of kilometers when it breaks on shore it can reach 30m high

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