1. Earthquakes!

2. Seismic Waves General Info  Seismic waves are the energy released when rocks break along faults.  Focus = the point within the Earth’s Interior at which this energy is first released.  Seismic waves are produced and travel outward from the earthquake focus.  Are Seismic Waves Compressional or Transverse Waves? – Why??

3. Epicenter  EQ Epicenter = the point on the Earth’s surface directly above the earthquake’s focus.  The speeds of seismic waves allows us to determine how far away earthquake epicenter is from a seismic station.  Measured with Seismograph.

4. “Body” Waves 1) P-waves (Primary Waves) 1) Fastest Seismic Wave  Cause particles in rocks to move back & forth in same direction. Ex: Stretched Spring, Compressional / Sound Wave. Ex: Stretched Spring, Compressional / Sound Wave. 2) S-waves (Secondary Waves)  Cause particles in rocks to move at right angles to the direction of the wave travel. Ex: Ocean Wave, Transverse Wave.

5. Surface Waves  Move rock particles in a rolling, side-to-side, swaying motion.  Most damaging type of seismic waves.

6. Measuring EQ’s  Richter Scale Used to measure the strength of an earthquake. Used to measure the strength of an earthquake. Based on the height of the lines on the seismograph. Based on the height of the lines on the seismograph. Scale has no upper limit, but 9.5 is estimated maximum. Scale has no upper limit, but 9.5 is estimated maximum.

7. Measuring EQ’s  Mercalli Intensity Scale Used to measure the intensity of an earthquake based on the amount of damage caused by the earthquake. Used to measure the intensity of an earthquake based on the amount of damage caused by the earthquake. Scale has 12 levels. Scale has 12 levels.