1. Earthquakes
Photo credit: USGS

2. Causes of Earthquakes Types and Behavior of Seismic Waves Body Waves
Primary or Compressional
Secondary or Shear
Surface Waves
Raleigh (large vertical displacements)
Love (shear)

3. Elastic Rebound Theory
3 m offset
1906 San Francisco Earthquake

4. Elastic Rebound Animation

5. Offset Lettuce Rows - El Centro, CA

6. Earthquake Focus and Hypocenter

7. Earthquake Focus Animation

8. Seismic Wave Types
Body Waves
Surface Waves

9. equations for velocities
Vp = k + 4/3µ r
1/2 r
density
shear modulus (rigidity)
Vs = µ r k
bulk modulus (rigidity)
1/2
because shear modulus (rigidity) for fluid is zero,
S waves cannot propagate through a fluid
consequence of equations is that P waves are 1.7x faster than S
can infer physical properties from P and S waves

10. Wave Animations

11. Locating and Measuring Earthquakes
Determining the Location of an Earthquake
Measuring the Size of an Earthquake
Location and Size of Earthquakes in the United States

12. Vertical Component Seismometer

13. Horizontal Component Seismomter

14. Seismograph Animation

15. First Arrivals - Seismographic Records

16. Distance - Time Relations

17. P vs. S Wave Travel Time Curves

18. Earthquake Location by Range

19. Effects of Earthquakes
Tsunamis
World Distribution of Earthquakes
First-Motion Studies of Earthquakes

20. Modified Mercalli Intensity Index (1931)
1886 Charleston, SC earthquake

21. Pancaked Building - 1985 Mexico City
Earthquakes don’t kill people - buildings do!