1. Earthquakes
Section 17.2

2. Earthquakes Shaking of the Earth’s crust caused by a release of energy
Build-up of stress
Stress overcomes friction
Plates slip (EQ)
Land snaps back into original shape

3. 3. Earthquakes Focus – point UNDERGROUND where movement starts
Epicenter – point ON THE SURFACE directly above focus

4. 3. Earthquakes Seismic Waves: Body Waves P-Waves aka “Primary Waves”
Compressional wave movement
Travel through solids, liquids, and gasses

5. 3. Earthquakes Seismic Waves: Body Waves S-Waves aka “Secondary Waves”
Arrive second, slower than p-waves
Side-to-side wave movement
Travel through solids ONLY

6. 3. Earthquakes Seismic Waves: Surface Waves L-Waves
aka “Land Waves” or “Surface Waves”
Last waves to occur
Cause most damage
Rayleigh Waves or Love Waves

7. 3. Earthquakes P S Body Wave Mantle Outer Core (liquid)
Inner Core (solid) P
Speed up, refract
Slow down
Speed up S
STOP

8. 3. Earthquakes

9. 3. Earthquakes

10. Collapse Because Lack of Shear Walls
San Fernando, Ca 1971
Loma Prieta, Ca 1986
San Francisco