Download Earthquakes

Shaking Things Up!
Q1
• Earthquakes are natural vibrations of the ground
caused by movement along gigantic fractures in
Earth’s crust.
Earthquakes
Unit Essential Question:
How does the Earth recycle and renew its surface?
Presentation Objectives:
§ Describe the three types of stress that can cause an earthquake.
§ Connect the three types of stress to the different types of faults.
§ Define epicenter and focus.
§ Describe the three types of waves generated by an earthquake.
§ Explain how information about earthquakes is collected and used to locate an epicenter.
§ Review the different scales used to measure an earthquake.
• Most earthquakes occur when rocks deep in the earth
fracture, which means that they break.
• Others are caused by volcanic eruptions.
Q2
Stressed Out!
Q3
One For One
• Since there are three types of stress and there are three
types of faults.
• A fracture in Earth’s crust is known as a fault.
• Faults are created when a large amount of stress is applied to a
rock or if the stress is applied too quickly.
• Reverse fault is the result of compression.
• Normal fault is the result of tension.
• Strike-slip fault is the result of shear.
• There are three types of stress.
Tension
Compression
Reverse
Normal
Strike-Slip
Shear
Spreading The Energy
• Earthquakes are the result of energy being released
when rocks move along a fault.
• This energy causes the earth to vibrate.
• These vibrations are known as seismic waves.
Q4
Everything Comes in Threes!
• Every earthquake generates three types of seismic waves.
• P-waves: Primary waves
•
•
• Seismic waves spread out from
the point of failure.
• This point is known as the focus
and is located deep within the
earth’s surface.
• The point on Earth’s surface
directly above the focus is known
as the epicenter.
First seismic waves to arrive.
Particle movement is in the
same direction as wave
movement.
S-waves: Secondary waves
•
•
•
Second seismic waves to arrive.
Particle movement is in
perpendicular to wave
movement.
Q5
Everything Comes in Threes!
Q5
• Surface Waves
• Last waves to arrive at a given location.
• Particle movement is in two dimensions as wave moves.
• Very similar to the movement of an ocean wave.
Recording The Data
Q7
• A seismograph is a record of an earthquake’s seismic waves.
• Recorded by a seismometer.
• Most seismographs are created using a suspended mass.
• It wants to stay were it is while the ground moves.
• The pen attached makes waves on the paper attached to the
bottom of the seismometer.
Measuring Earthquakes
Q6
• The magnitude of an earthquake is often measured using the
Richter Scale.
• Measures the amount of energy released during an earthquake.
• Each successive number in the scale represents an increase in
seismic wave size of a factor of 10.