1. Earthquakes

2. What is an earthquake?
Used to describe both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip
Caused by volcanic or magmatic activity,
Caused by other sudden stress changes in the earth.

3. Three Types of Faults Transform Reverse Normal Three types of faults
Form depending on type of plate motion and complex reaction of earth’s lithospheric blocks
Strike-slip
Normal
Thrust
Normal

4. What causes earthquakes?
Tectonic plates move past each other causing stress. Stress causes the rock to deform
Plastic deformation – does not cause earthquakes
Elastic deformation – rock stretches then reaches a breaking point, releasing energy.

5. Elastic Rebound – deformed rock goes back to its original shape

6. Focus –. point inside the Earth where an
Focus – point inside the Earth where an earthquake begins Epicenter – point on Earth’s surface above focus

7. Typical Seismogram

8. Primary Waves (P Waves)
A type of seismic wave that compresses and expands the ground
The first wave to arrive at an earthquake

9. Secondary Waves (S Waves)
A type of seismic wave that moves the ground up and down or side to side

10. Comparing Seismic Waves

11. Surface Waves Move along the Earth’s surface
Produces motion in the upper crust
Motion can be up and down
Motion can be around
Motion can be back and forth
Travel more slowly than S and P waves
Most destructive but only affect local area

12. How do scientists calculate how far a location is from the epicenter of an earthquake?
Scientists calculate the difference between arrival times of the P waves and S waves
The further away an earthquake is, the greater the time between the arrival of the P waves and the S waves

13. Locating Earthquakes

14. Locating Earthquakes

15. Locating Earthquakes

16. How are Earthquakes Measured? Richter Scale

17. How are Earthquakes Measured? Mercalli Intensity Scale
Click Link for Interactive Demo

18. Earthquake Waves & Earth’s Interior

19. How do we know the inner core is solid? The “shadow zone”.

20. Seismic Waves in the Earth

21. Tsunamis

22. Formation of a tsunami

23. Tsunami Warning System