1. Chapter 11
Earthquakes

2. Section 1 & 2
Earthquake Formation

3. Fault formation
When rocks undergo large amounts of pressure,
the rock may break.
When rocks break, they move along surfaces
called faults.

4. What causes faults?
Plates moving put stress on rocks near plate
edges, causing rocks to bend compress, stretch,
or break.
Earthquakes are the vibrations produced by the
breaking of rock.

5. How earthquakes occur
Rocks move past each other at faults
Rough surfaces catch
Movement of fault is stopped
Forces keep driving rocks to move
This stress causes rocks to break, move along, fault,
and return to original shape
Earthquake occurs.
Range from unnoticeable to devastating

6. 3 types of faults
Normal
Reverse (Thrust)
Strike-Slip

7. Normal fault
Tension causes rocks to be pulled apart
Rock above the fault surface moves downward
ANIMATION:
http://earthquake.usgs.gov/learn/animations/animation.php?
flash_title=Normal+Fault&flash_file=normalfault&flash_width=22
0&flash_height=320

8. Reverse faults
Compression forces squeeze rocks
Rock above reverse fault surface forced up and
over rock below fault surface
ANIMATION:
http://earthquake.usgs.gov/learn/animations/animation.php?
flash_title=Thrust+Fault+and+Reverse+Fault&flash_file=thrustfault&flas
h_width=220&flash_height=320

9. Strike slip fault
Rocks are moving past each other without much
upward and downward movement-called shear
Ex: San Andreas Fault
ANIMATION:
http://earthquake.usgs.gov/learn/animations/animation.php?flash_title=S

10. Seismic Waves
Waves generated by an earthquake that travel
through the earth
Focus (foci if plural): point where energy release first
occurs
3 types:
Primary waves
Secondary waves
Surface waves

11. Primary waves
P-waves
Particles move back and forth in the
direction that the wave is travelling
Like waves through a spring

12. Secondary waves
Secondary waves (s waves)
Particles move at right angles to the direction of wave
travel (up and down)

13. Surface waves
Surface waves
Particles move in a backward, rolling motion and side
to side in a swaying motion
Cause buildings to fall

14. Locating an Epicenter
Different seismic waves travel at different speeds:
Primary are fastest, then secondary, finally
surface
Scientists use the different speeds to determine
distance to the epicenter

15. Measuring Seismic Waves
Seismograph: measures the time seismic waves arrive

16. Seismograph Stations
Seismographs are located all over the US and world
If waves reach three or more stations, the
epicenter can be determined
Draw a circle around each station-the radius of
each circle equals station's distance from
epicenter
Point where circles meet is epicenter

17. Bibliography
Images
"2010 Haiti Earthquake." Wikipedia. Wikimedia Foundation, 26 June 2012. Web. 29 June
2012. <http://en.wikipedia.org/wiki/2010_Haiti_earthquake>.
"Earthquake Glossary." Earthquake Glossary. USGS, 2009. Web. 29 June 2012.
<http://earthquake.usgs.gov/learn/glossary/>.
"Fault (geology)." Wikipedia. Wikimedia Foundation, 29 June 2012. Web. 29 June 2012.
<http://en.wikipedia.org/wiki/Fault_(geology)>.
Information
National Geographic Society, Ralph M. Feather, Susan L. Snyder, and Dinah Zike. Earth
Science. N.p.: Glencoe, 2002. Print.