EarthquakesThe 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