Seismic Waves

What do we know?• Energy that travels through the earth caused by the sudden breaking of rock within the earth or an explosion

•Examples?

Types of Waves

• P-waves– The fastest kind of seismic wave– The P wave can move through solid rock and

fluids, like water or the liquid layers of the earth.

• S-waves– An S wave is slower than a P wave and can only

move through solid rock, not through any liquid medium.

P-waves

It pushes and pulls the rock it moves through

S-waves

S waves move rock particles up and down, or side-to-side--perpendicular to the direction that the wave is traveling in

Earthquakes

• Earthquakes and seismic waves?

• Think for two minutes with your partner about the relation between earthquakes and seismic waves.

Earthquakes cont.

• Seismic movement• Intensity (strength) can fluctuate• Usually last a short time

• Question: Where does the majority of seismic activity take place?

How do we Measure Earthquakes?

• Intensity – Based on perceived sensations and effects and

measured by the M.S.K. scale.

• Magnitude – Measures the amount of energy released by an

earthquake. Measured by the Richter scale.

Richter Scale

Analyze

• Where does the earthquake originate?• Where does one feel the earthquake?• Will the epicenter always be directly above the focus?

Seismic Risks

• The earth’s crust (or land) shifts and moves causing earthquakes and tsunamis (tidal waves).

Prevention/Prediction

Seismometer: instruments used to measure motions in the ground and the seismic waves generated by earthquakes and volcanic eruptions

Review

Review cont.

• Is this a P or S wave?

Review cont.

• Is this a P or S wave?

Review cont.