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Lesson 3 How do Earthquake Waves Travel? • Energy released from moving plates and faults travels through the Earth as waves. • These waves are called seismic waves. Types of Seismic Waves 1. BODY WAVES: Seismic waves that travel through the Earth. 2. SURFACE WAVES: Seismic waves that travel along the surface. • WAVES TRAVEL: 1.At different speeds and 2 In different ways Depending on what kind of material they are moving through. Body Waves • There are two types of body waves: • P-waves • S-waves P-waves • • • • P-waves are pressure waves. P-waves travel through solid, liquids and gases. P-waves are the fastest waves. P-waves are the first waves to be detected and the first waves to arrive. • P-waves are also called primary waves because they arrive first. • P-waves cause rock to squeeze and stretch. Imagine a slinky! • The area of the Earth that does not receive seismic energy is called the shadow zone. S-waves • S-waves are the second fastest waves. • S-waves are also called secondary waves because they arrive second. • S-waves are slower than P-waves. • S-waves move rock from side to side. • S-waves can’t travel through parts of the Earth that are completely liquid. Surface Waves • Surface waves move along the surface of the Earth. • Surface waves can move up, down and around or side to side. • Surface waves move the slowest and cause the most destruction. Seismic Wave Arrival • First- P-waves • Second- S-waves • Third- Surface Waves Shadow Zone The shadow zone results from S waves being stopped entirely by the liquid core and P waves being bent (refracted) by the liquid core. Moho Zone • The Moho is the boundary between the crust and the mantle in the earth. This is a depth where seismic waves change velocity, or speed. They tend to increase at the location. Quiz • • • • • • 1. Most Earthquakes occur along ________________. 2. The first seismic waves to arrive are______________. 3. The second seismic waves to arrive are _____________. 4. The last seismic waves to arrive are_______________. 5. Which seismic waves travel the fastest?___________ 6. Which type of seismic wave can move through a solid, liquid or a gas?________________ • 7. Which seismic wave cannot travel through material that is completely liquid?______________ • 8. Which seismic waves are the slowest and the most destructive?_______________