1. How and where are earthquake waves detected and recorded? A seismograph is an instrument that records earthquake waves. It is also used to determine the magnitude of an earthquake the location of its epicenter.

2. Anatomy of Earthquakes

3. A seismograph designed to record vertical ground motion

4. A seismograph designed to record horizontal ground motion

5. Typical Seismogram

6. Seismograph measuring horizontal displacement

7. Compressional Wave (P-Wave) Animation Particle motion consists of alternating compression and dilation (enlargement & reduction). Particle motion is parallel to the direction of propagation (longitudinal). Material returns to its original shape after wave passes.

8. Shear Wave (S-Wave) Animation Particle motion consists of alternating transverse motion. Particle motion is perpendicular to the direction of propagation. Transverse particle motion shown here is vertical but can be in any direction

9. Surface Wave (L-Wave) Animation Particle motion consists of alternating transverse motions. Particle motion is horizontal and perpendicular to the direction of propagation (transverse).

10. Seismology Types of seismic waves  Body waves  Travel through Earth’s interior  Two types based on mode of travel  Primary (P) waves  Push-pull (compress and expand) motion, changing the volume of the intervening material  Travel through solids, liquids, and gases  Generally, in any solid material, P waves travel about 1.7 times faster than S waves

11. Seismology Types of seismic waves  Surface waves  Travel along outer part of Earth  Cause greatest destruction  Waves exhibit greatest amplitude and slowest velocity  Waves have the greatest periods (time interval between crests)  Often referred to as long waves, or L waves

12. Seismology Types of seismic waves  Body waves  Secondary (S) waves  Shake" motion at right angles to their direction of travel  Travel only through solids  Slower velocity than P waves  Slightly greater amplitude than P waves

13. Locating the source of earthquakes Terms  Focus - the place within Earth where earthquake waves originate  Epicenter – location on the surface directly above the focus Epicenter is located using the difference in velocities of P and S waves

14. Draw the diagram on page 215 and write down the information on each caption. What is the relationship between particle density and seismic wave? How and where are Earthquakes recorded? (page 217) Summarize how the magnitude of an earthquake is measured.

15. A time-travel graph is used to find the distance to the epicenter