1. Modified from Liz LaRosa http://www.middleschoolscience.com
Earthquakes
Modified from Liz LaRosa

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

3. Three Types of Faults Strike-Slip Thrust 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, causing an earthquake and releasing energy.

5. Elastic Rebound – after the earthquake, 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. How Seismographs Work
the pendulum remains fixed as the ground moves beneath it

8. Typical Seismogram

9. Two Types of SeismicWaves
Surface Waves
Body Waves
Primary (P Waves)
Secondary (S Waves)

10. Primary Waves (P Waves) – Pressure Waves
A type of seismic wave that compresses and expands the ground (longitudinal)
The first wave to arrive at an seismic station
Can travel through solids, liquids and gases

11. Secondary Waves (S Waves) –Shear Waves
A type of seismic wave that moves the ground up and down or side to side (transverse)
Arrives at the seismic station second
Can’t travel through liquids

12. Comparing Seismic Waves

13. 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
More destructive than S and P waves

14. 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

15. Locating Earthquakes

16. Locating Earthquakes

17. Locating Earthquakes

18. How are Earthquakes Measured? Richter Scale

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

20. Earthquake Waves & Earth’s Interior

21. Seismic Waves in the Earth

22. Tsunamis

23. Formation of a tsunami

24. Tsunami Warning System