About and the causes of earthquake

1. Earthquakes
Liz LaRosa http://www.middleschoolscience.com 2009
for my 5th
grade science class 2009

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
Strike-Slip
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
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

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

7. How Seismographs Work
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM
the pendulum remains
fixed as the ground
moves beneath it

8. Typical Seismogram
http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt

9. Primary Waves (P Waves)
• A type of seismic wave that compresses
and expands the ground
• The first wave to arrive at an
earthquake
http://daphne.meccahosting.com/~a0000e89/insideearth2.htm

10. Secondary Waves (S Waves)
• A type of seismic wave that moves the
ground up and down or side to side
http://daphne.meccahosting.com/~a0000e89/insideearth2.htm

11. Comparing Seismic Waves

12. 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

13. 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

14. Locating Earthquakes
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

15. Locating Earthquakes
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

16. Locating Earthquakes
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

17. How are Earthquakes Measured?
Richter Scale

18. How are Earthquakes Measured?
Mercalli Intensity Scale
Click Link for Interactive Demo
http://elearning.niu.edu/simulations/images/S_portfolio/Mercalli/Mercalli_Scale.swf

19. Earthquake Waves & Earth’s Interior

20. Seismic
Waves in
the Earth
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

21. Tsunamis
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

22. Formation of a tsunami
http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt

23. Tsunami Warning System
http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt