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Earthquakes DYNAMIC EARTH

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Page 1: Earthquakes · Three Types of Faults Strike-Slip Thrust Normal. What causes earthquakes? •Tectonic plates move past each other causing stress. Stress causes the rock to deform –Plastic

Earthquakes

DYNAMIC EARTH

Page 2: Earthquakes · Three Types of Faults Strike-Slip Thrust Normal. What causes earthquakes? •Tectonic plates move past each other causing stress. Stress causes the rock to deform –Plastic

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.

Page 3: Earthquakes · Three Types of Faults Strike-Slip Thrust Normal. What causes earthquakes? •Tectonic plates move past each other causing stress. Stress causes the rock to deform –Plastic

Three Types of Faults

Strike-SlipThrust

Normal

Page 4: Earthquakes · Three Types of Faults Strike-Slip Thrust Normal. What causes earthquakes? •Tectonic plates move past each other causing stress. Stress causes the rock to deform –Plastic

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.

Page 5: Earthquakes · Three Types of Faults Strike-Slip Thrust Normal. What causes earthquakes? •Tectonic plates move past each other causing stress. Stress causes the rock to deform –Plastic

Elastic Rebound – deformed rock goes back to its original shape

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

Page 6: Earthquakes · Three Types of Faults Strike-Slip Thrust Normal. What causes earthquakes? •Tectonic plates move past each other causing stress. Stress causes the rock to deform –Plastic

Focus – point inside the Earth where an earthquake begins

Epicenter – point on Earth’s surface above focus

Page 7: Earthquakes · Three Types of Faults Strike-Slip Thrust Normal. What causes earthquakes? •Tectonic plates move past each other causing stress. Stress causes the rock to deform –Plastic

How Seismographs Work

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

the pendulum remains

fixed as the ground

moves beneath it

Page 8: Earthquakes · Three Types of Faults Strike-Slip Thrust Normal. What causes earthquakes? •Tectonic plates move past each other causing stress. Stress causes the rock to deform –Plastic

Typical Seismogram

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

Page 9: Earthquakes · Three Types of Faults Strike-Slip Thrust Normal. What causes earthquakes? •Tectonic plates move past each other causing stress. Stress causes the rock to deform –Plastic

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

Page 10: Earthquakes · Three Types of Faults Strike-Slip Thrust Normal. What causes earthquakes? •Tectonic plates move past each other causing stress. Stress causes the rock to deform –Plastic

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

Page 11: Earthquakes · Three Types of Faults Strike-Slip Thrust Normal. What causes earthquakes? •Tectonic plates move past each other causing stress. Stress causes the rock to deform –Plastic

Comparing Seismic Waves

Page 12: Earthquakes · Three Types of Faults Strike-Slip Thrust Normal. What causes earthquakes? •Tectonic plates move past each other causing stress. Stress causes the rock to deform –Plastic

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

Page 13: Earthquakes · Three Types of Faults Strike-Slip Thrust Normal. What causes earthquakes? •Tectonic plates move past each other causing stress. Stress causes the rock to deform –Plastic

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

Page 14: Earthquakes · Three Types of Faults Strike-Slip Thrust Normal. What causes earthquakes? •Tectonic plates move past each other causing stress. Stress causes the rock to deform –Plastic

How are Earthquakes Measured? Richter Scale

Page 15: Earthquakes · Three Types of Faults Strike-Slip Thrust Normal. What causes earthquakes? •Tectonic plates move past each other causing stress. Stress causes the rock to deform –Plastic

How are Earthquakes Measured? Mercalli Intensity Scale

Click Link for Interactive Demo

http://elearning.niu.edu/simulations/images/S_portfolio/Mercalli/Mercalli_Scale.swf

Page 16: Earthquakes · Three Types of Faults Strike-Slip Thrust Normal. What causes earthquakes? •Tectonic plates move past each other causing stress. Stress causes the rock to deform –Plastic

Formation of a tsunami

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