1. Chapter 12: Earthquakes

2. Earthquake
sudden release of energy from a fault (crack in a body of rock)
“locked” faults undergo stress…they deform, slip, and then rebound

3. Elastic rebound
sudden return
to Earth’s
un-deformed
shape

5. BODY WAVES travel through Earth
Begins at FOCUS
Point directly above – EPICENTER
Vibrations – SEISMIC WAVES

6. Seismic Waves P waves: compression waves, parallel, Fastest
S waves: shear waves, perpendicular, ONLY IN SOLIDS, 2nd Fastest
Surface waves: travel along the surface, slowest moving, GREATEST DAMAGE

8. Measuring seismic waves detects Earth’s internal layers
*Measuring seismic waves detects Earth’s internal layers *Earth’s interior can change the size and/or direction of seismic waves

9. Convergent Oceanic —plates move toward each other and collide
Convergent Oceanic —plates move toward each other and collide. Divergent Oceanic —(mid-ocean ridges)—plates move away from each other. Continental -convergent/divergent/transform

10. Recording Earthquakes
Seismograph – machine
Seismogram – recording/report
The closer S+P
waves are, the closer to the earthquake

11. Measuring Earthquakes
Moment Magnitude (BEST): magnitude scale based on size of the fault area, how far fault blocks move, and rigidity of the rocks
Richter Scale: measures ground motion
Modified Mercalli Scale: measures basic EQ intensity (after effects)

14. *Buildings may sway or collapse, constructed to “sway”

15. U.S. Earthquake Risk Map