Download What Are Earthquakes? - Human Resources Department

How to Use
This Presentation
• To View the presentation as a slideshow with effects
select “View” on the menu bar and click on “Slide Show”,
or simply press F5 on the top row of your keyboard.
• To advance to the next slide click the left mouse button once.
• From the Chapter screen you can click on any section to go
directly to that section’s presentation.
• Blank or “missing” areas of a slide will remain hidden until the
left mouse button is clicked.
• You may exit the slide show at any time by pressing
the Esc key
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Module F: Chapter 5
Earthquakes
Section 1: What Are Earthquakes?
Section 2: Earthquake Measurement
Section 3: Earthquakes and Society
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 1
What Are Earthquakes?
Bellringer
What do you think an earthquake is? Do you think the way
earthquakes are portrayed on television and in movies is
accurate? Why or why not?
Write your answer in your science journal.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 1
What Are Earthquakes?
Objectives
• Explain where earthquakes take place.
• Explain what causes earthquakes.
• Identify three different types of faults that occur at plate
boundaries.
• Describe how energy from earthquakes travels through
the Earth.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 1
What Are Earthquakes?
Where Do Earthquakes Occur?
• Tectonic Plates Most earthquakes take place near the
edges of tectonic plates.
• Faults As a result of tectonic plate movements, numerous
features called faults exist in the Earth’s crust. A fault is a
break in the Earth’s crust along which blocks of the crust
slide relative to one another. Earthquakes occur along
faults because of this sliding.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 1
What Are Earthquakes?
What Causes Earthquakes?
• Deformation Elastic deformation leads to earthquakes.
• Elastic Rebound The sudden return of elastically
deformed rock to its original shape is called elastic
rebound. Elastic rebound is illustrated on the next slide.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 1
Elastic Rebound
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 1
What Are Earthquakes?
Faults at Tectonic Plate Boundaries
• Plate Motion Transform plate motion causes a strike-slip
fault. Convergent plate motion causes a reverse fault.
Divergent plate motion causes a normal fault.
• Earthquake Zones Most earthquakes happen in the
earthquake zones along tectonic plate boundaries.
Earthquake zones are places where a large number of
faults are located.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 1
What Are Earthquakes?
How Do Earthquakes Travel?
• P Waves Waves that travel through solids, liquids, and
gases are called P waves (pressure waves).
• S Waves After being deformed from side to side, the rock
springs back to its original position and S waves are
created. S waves, or shear waves, are the second-fastest
seismic waves.
• Surface Waves Surface waves move along the Earth’s
surface and produce motion mostly in the upper few
kilometers of Earth’s surface.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 2
Earthquake Measurement
Bellringer
Create a qualitative scale for gauging earthquake
intensity. Describe the effects of very minor earthquakes
and extreme earthquakes. What kind of damage would be
done to buildings, water and power supplies, animals,
forests, and people?
Record your response in your science journal.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 2
Earthquake Measurement
Objectives
• Explain how earthquakes are detected.
• Describe how to locate an earthquake’s epicenter.
• Explain how the strength of an earthquake is measured.
• Explain how the intensity of an earthquake is measured.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 2
Earthquake Measurement
Locating Earthquakes
• Determining Time and Location of Earthquakes
Seismologists use seismograms to calculate when an
earthquake began. Seismologists also use seismograms to
find an earthquake’s epicenter.
• The S-P Time Method Perhaps the simplest method by
which seismologists find an earthquake’s epicenter is the
S-P time method. The next slide illustrates how the S-P
time method can be used to find an earthquake’s epicenter.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 2
Finding an Earthquake Epicenter
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 2
Earthquake Measurement
Measuring Earthquake Strength and Intensity
• The Richter Magnitude Scale Throughout much of the
20th century, seismologists used the Richter magnitude
scale, commonly called the Richter scale, to measure the
strength of earthquakes.
• Earthquake Ground Motion The Richter scale measures
the ground motion from an earthquake and adjusts for
distance to find its strength.
• Modified Mercalli Intensity Scale Currently,
seismologists in the United States use the Modified Mercalli
Intensity Scale to measure earthquake intensity.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 3
Earthquakes and Society
Bellringer
If you have ever experienced an earthquake, write a short
paragraph describing how you felt and what you did to
protect yourself during the quake. If you have not
experienced an earthquake, write a paragraph describing
what you think you would do during a moderate
earthquake. Do you know what to do in an earthquake,
fire, tornado, or serious storm?
Write your responses in your science journal.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 3
Earthquakes and Society
Objectives
• Explain how earthquake-hazard level is determined.
• Compare methods of earthquake forecasting.
• Describe five ways to safeguard buildings against
earthquakes.
• Outline earthquake safety procedures.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 3
Earthquakes and Society
Earthquake Hazard
• What Is Earthquake Hazard? Earthquake hazard is a
measurement of how likely an area is to have damaging
earthquakes in the future.
• Area with a High Hazard The West Coast of the United
States has a very high earthquake-hazard level because it
has a lot of seismic activity.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 3
Earthquakes and Society
Earthquake Forecasting
• Strength and Frequency The strength of earthquakes is
related to how often they occur.
• The Gap Hypothesis The gap hypothesis is a hypothesis
that states that sections of active faults that have had
relatively few earthquakes are likely to be the sites of
strong earthquakes in the future.
• Using the Gap Hypothesis Some seismologists think the
gap hypothesis helped forecast the approximate location
and strength of the 1989 Loma Prieta earthquake.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 3
Earthquakes and Society
Earthquakes and Buildings
• Retrofitting The process of making older structures more
earthquake resistant is called retrofitting.
• Earthquake Resistant Buildings Architects and
engineers use the newest technology to design and
construct buildings and bridges to better withstand
earthquakes.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 3
Earthquakes and Society
Are You Prepared for an Earthquake?
• Before the Shaking Starts The first thing you should do
is safeguard your home against earthquakes. Next, you
should find safe places within each room of your home and
outside of your home.
• When the Shaking Starts The best thing to do if you are
indoors when an earthquake begins is to crouch or lie face
down under a table or desk in the center of a room.
• After the Shaking Stops Remove yourself from
immediate danger, such as downed power lines and broken
glass. Be aware that there may be aftershocks.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Earthquakes
Concept Map
Use the following terms to complete the concept map on
the next slide: seismograph, seismic waves, earthquakes,
surface waves, body waves, S waves.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Concept Map
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Concept Map
Copyright © by Holt, Rinehart and Winston. All rights reserved.