This is the earthquake power point you saw in class. Feel free to take notes on it or view the animations again.

1. Earthquakes
What Is An Earthquake? Click here to find out
Adapted from powerpoint by Liz LaRosa http://www.middleschoolscience.com 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 plate activity,
http://eqseis.geosc.psu.edu
The map above shows the distribution of earthquakes with magnitudes greater
than 5.0 that occurred between 1965 and 1995.

3. Three Types of Faults
Strike-Slip
Animation of fault movement
Reverse
Normal

4. Normal fault
Pulls on the crust stretching rock so that it becomes thinner (like pulling
on bubble gum) =
Occurs when plates are moving apart
Hanging wall
Foot wall
Results in hanging wall slipping downward
animation

5. What type of fault?
normal
Hanging wall
Foot wall
http://www.bgs.ac.uk/eqr/GeoD_Structures.htm

6. What causes earthquakes?
• Tectonic plates move past each other causing
stress. Stress causes the rock to deform
– What type of fault boundary is this? transform
– What type of stress is shown? shearing

7. Strike – slip fault
Rocks on either side of fault slip past each other sideways with little
up or down motion What type of stress is produced?
Occurs at a transform plate boundary
Animation of strike-slip motion

8. Fault rupture across road in western Kaynasli, right-lateral strike slip displacement was
about 4.0 m (13 feet) at this location
http://www.geerassociation.org/GEER_Post%20EQ%2
0Reports/Duzce_1999/kaynasli1.htm

9. Reverse fault
Pushes on the crust squeezing rock until it folds or breaks (like a trash
compactor) =
Occurs when plates are moving together
Hanging wall
Foot wall
Results in hanging wall slipping upward
animation

10. What type of fault?
reverse
Hanging wall
Foot wall
http://geologicalintroduction.baffl.co.uk

11. What type of fault?
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

12. Focus – 1. point inside the Earth where an
earthquake begins
Epicenter – 2. point on Earth’s surface above focus where
earthquake is FELT most strongly
2
1

13. How Seismographs Work
A seismograph is an instrument used for recording the intensity and
duration of an earthquake.
the pendulum remains
fixed as the ground
moves beneath it
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

14. Earthquakes
• How are earthquakes measured?
Seismogram –
seismic wave
display record
Seismograph
machine

15. Seismic Waves

16. 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

17. 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

18. Comparing Seismic Waves

19. 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
Animation of wave types

20. 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

21. Typical Seismogram
How much time elapsed between the arrival of the
P wave (start) and the arrival of the S wave (finish)?
start
http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt
finish

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

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

24. Now you are going to be seismologists
and locate an Earthquake
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM
Go to: http://tinyurl.com/11quake13
Click here to go to virtual earthquake site

25. National Geographic earthquake information

26. How are Earthquakes Measured?
Richter Scale
A logarithmic scale
used to express the
total amount of
energy released
magnitude
___________ of an
earthquake. Its
values typically fall
between 0 and 9,
with each increase
of 1 representing a
10-fold
_________ increase
in energy.

27. How are Earthquakes Measured?
Mercalli Intensity Scale
A scale of earthquake intensity based on ___________
observed effects
and ranging from I (detectable only with instruments) to
XII (causing almost total destruction).
Click for Interactive Demo
Go to http://tinyurl.com/13quake13

28. Earthquake Waves & Earth’s Interior
Seismic wave animation

29. Seismic
Waves in
the Earth
Click here for animation
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

30. Tsunamis
Click here for explanation of a tsunami
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

31. Formation of a tsunami
a large ocean wave usually caused by an underwater earthquake
or a volcanic explosion.
PBS –tsunami animation
http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt

32. With typical waves, water flows in circles, but with a tsunami, water
flows straight. This is why tsunamis cause so much damage!
Click here for Japan helicopter view of tsunami

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

34. Review Questions
1. A large ocean wave usually caused by an
underwater earthquake or a volcanic explosion.
tsunami
2. Used to describe both a sudden slip on a fault,
and the resulting ground shaking and radiated
seismic energy caused by the slip
earthquake

35. How are Earthquakes Measured?
3. Which one uses a logarithmic scale to express the
total amount of energy released or magnitude of an
earthquake.
Richter Scale
4. Which uses a scale of earthquake intensity
based on observed effects and ranging from I
(detectable only with instruments) to XII (causing
almost total destruction).
Modified Mercalli Scale

36. What type of fault is shown by each picture?
1.
2.
Normal
Reverse
3.
Transverse
or strike-slip

37. S-wave

38. Surface or
Love waves

39. What type of fault?
Source: indiana.edu
http://geologicalintroduction.baffl.co.uk
A
Hanging wall has moved upward
Reverse fault
B
Strike –slip or
transverse fault

40. Focus – 1. point inside the Earth where an
earthquake begins
Epicenter – 2. point on Earth’s surface above focus where
earthquake is FELT most strongly
2
1

41. People walk along a damaged road in the province
of Bohol on Tuesday, October 15, 2013.
Do you think this was a major earthquake? Why or why not?

42. Yes, it was a major quake.
It crumbled a number of buildings
Such as this church
7.1 magnitude earthquake hit the Philippines

43. Earthquakes
3. Surface
1.
P-wave
2. S-wave
Seismogram
4. ____________
seismic wave
display record
5. Seismograph
__________
machine