Earthquakes presentation

Earthquakes

Chapter 11

Chapter 11

Chapter 11

Earthquakes

Section 1 & 2

Earthquake Formation

Fault formation

When rocks undergo large amounts of pressure, the rock may break.

When rocks break, they move along surfaces called faults.

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.

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

3 types of faults

Normal

Reverse (Thrust)

Strike-Slip

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=220&flash_height=320

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&flash_width=220&flash_height=320

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=Strike-Slip+Fault&flash_file=strikeslip&flash_width=240&flash_height=310

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

Primary waves

P-waves

Particles move back and forth in the direction that the wave is travelling

Like waves through a spring

Secondary waves

Secondary waves (s waves)

Particles move at right angles to the direction of wave travel (up and down)

Surface waves

Surface waves

Particles move in a backward, rolling motion and side to side in a swaying motion

Cause buildings to fall

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

Measuring Seismic Waves

Seismograph: measures the time seismic waves arrive

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

Bibliography

Images"2010 Haiti Earthquake." Wikipedia. Wikimedia Foundation, 26 June 2012. Web. 29 June 2012. .

"Earthquake Glossary." Earthquake Glossary. USGS, 2009. Web. 29 June 2012. .

"Fault (geology)." Wikipedia. Wikimedia Foundation, 29 June 2012. Web. 29 June 2012. .

InformationNational Geographic Society, Ralph M. Feather, Susan L. Snyder, and Dinah Zike. Earth Science. N.p.: Glencoe, 2002. Print.

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Earthquakes presentation