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Chapter Presentation

Transparencies

Image and Math Focus Bank

Bellringers

Standardized Test Prep

Visual Concepts

Resources



Earthquakes

Section 1 What Are Earthquakes? Section 2 Earthquake Measurement Section 3 Earthquakes and Society

Chapter F5

Table of Contents



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 answers in your science journal.

Chapter F5




• 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.

Objectives

Chapter F5




What Are Earthquakes?

• There is more to earthquakes than just the shaking

of the ground. An entire branch of Earth science,

called seismology, is devoted to the study of

earthquakes.

• Earthquakes are complex, and they present many

questions for seismologists, the scientists who

study earthquakes.

Chapter F5




Where Do Earthquakes Occur?

• Most earthquakes take place near the edges of

tectonic plates. This figure shows the Earth’s tectonic

plates and the locations of recent major earthquakes.

Chapter F5




Where Do Earthquakes Occur?, continued

• Tectonic plates move in different directions and at

different speeds. As a result, 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.

Chapter F5




What Causes Earthquakes?

• As tectonic plates move, stress increases along

faults near the plates’ edges. In response to this

stress, rock in the plates deforms.

• Deformation is the change in the shape of rock

in response to the stress of bending, tilting, and

breaking of the Earth’s crust.

Chapter F5




What Causes Earthquakes?, continued

• Rock along a fault deforms in mainly two ways.

• Rock deforms in a plastic manner, like a piece of

molded clay, or in an elastic manner, like a rubber

band.

• Plastic deformation does not lead to earthquakes.

Elastic deformation does. Like a rubber band, rock

can be stretched only so far before it breaks.

Chapter F5




What Causes Earthquakes?, continued

• Elastic rebound is the sudden return of elastically

deformed rock to its undeformed shape. Elastic

rebound occurs when more stress is applied to rock

than the rock can withstand.

• During elastic rebound, energy is released. Some

of this energy travels as seismic waves, which cause

an earthquake.

Chapter F5




Elastic Deformation and Elastic Rebound

Click below to watch the Visual Concept.

You may stop the video at any time by pressing

the Esc key.

Visual Concept

Chapter F5

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Faults at Tectonic Plate Boundaries

• A specific type of plate motion takes place at

different tectonic plate boundaries.

• Each type of motion creates a particular kind of

fault that can produce earthquakes.

Chapter F5




Faults at Tectonic Plate Boundaries, continued

• Transform motion occurs where two plates slip

past each other, creating strike-slip faults. Blocks

of crust slide horizontally past each other.

Chapter F5





• Convergent motion

occurs where two

plates push together,

creating reverse

faults. Blocks of crust

that are pushed

together slide along

reverse faults.

Chapter F5





• Divergent motion

occurs where two

plates pull away from

each other, creating

normal faults. Blocks

of crust that are pulled

away from each other

slide along normal

faults.

Chapter F5





• 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.

• Not all faults are located at tectonic plate

boundaries. Sometimes, earthquakes happen

along faults in the middle of tectonic plates.

Chapter F5




How Do Earthquake Waves Travel?

• Waves of energy that travel through the Earth away

from an earthquake are called seismic waves.

• Seismic waves that travel along the Earth’s surface

are called surface waves.

Chapter F5




Seismic Waves: Surface Waves



the Esc key.

Visual Concept

Chapter F5

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How Do Earthquake Waves Travel?, continued

• Seismic waves that travel through Earth’s interior

are called body waves. There are two types of body

waves: P waves and S waves.

• P waves are seismic waves that cause particles of

rock to move in a back-and-forth direction.

• S waves are seismic waves that cause particles of

rock to move in a side-to-side direction.

Chapter F5



Section 1 What Are Earthquakes? Chapter F5



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?

Chapter F5




• 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.

Objectives

Chapter F5




Locating Earthquakes

• Scientists use seismographs to study earthquakes.

• A seismograph is an instrument that records

vibrations in the ground and determines the location

and strength of an earthquake.

• When earthquake waves reach a seismograph, it

creates a seismogram, a tracing of the earthquake’s

motion.

Chapter F5




Locating Earthquakes, continued

• Determining Time and Location of Earthquakes

Seismograms are used to find an earthquake’s

epicenter.

• An epicenter is the point on the Earth’s surface

directly above an earthquake’s starting point.

Chapter F5





• A focus is the point inside the Earth where an

earthquake begins.

• An earthquake’s epicenter is on the Earth’s surface

directly above the earthquake’s focus.

Chapter F5





• The S-P Time Method is perhaps the simplest

method by which seismologists find an earthquake’s

epicenter.

• This method is explained in the following Visual

Concepts presentation.

Chapter F5




S and P Time Method: Finding an Epicenter



the Esc key.

Visual Concept

Chapter F5

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Measuring Earthquake Strength and Intensity

• The Richter Magnitude Scale Throughout much

of the 20th century, seismologists used a scale

created by Charles Richter to measure the strength

of earthquakes.

• Earthquake Ground Motion A measure of the

strength of an earthquake is called magnitude. The

Richter scale measures the ground motion from an

earthquake and adjusts for distance to find its

strength.

Chapter F5




Richter Scale



the Esc key.

Visual Concept

Chapter F5

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Measuring Earthquake Strength, continued

• Modified Mercalli Intensity Scale A measure of

the degree to which an earthquake is felt by people

and the damage it caused is called intensity.

• Currently, seismologists use the Modified Mercalli

Intensity Scale to measure earthquake intensity. This

is a numerical scale that uses Roman numerals from I to XII to describe earthquake intensity levels.

Chapter F5




Measuring Earthquake Strength, continued

• In the Modified Mercalli Intensity Scale, an intensity of I describes an earthquake that is not felt by most

people. An intensity level of XII indicates total

damage of an area.

• Because the effects of an earthquake vary based

on location, any earthquake will have more than one

intensity value. Intensity values usually are higher

near the epicenter.

Chapter F5



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?

Chapter F5




• Explain how earthquake-hazard level is determined.

• Compare methods of earthquake forecasting.

• Describe five ways to safeguard buildings against

earthquakes.

• Outline earthquake safety procedures.

Objectives

Chapter F5




Earthquake Hazard

• Earthquake hazard is a measurement of how likely

an area is to have damaging earthquakes in the

future.

• An area’s earthquake-hazard level is determined by

past and present seismic activity.

• The greater the seismic activity, the higher the

earthquake-hazard level.

Chapter F5




Earthquake-Hazard Level



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Visual Concept

Chapter F5

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Earthquake Forecasting

• Forecasting when and where earthquakes will

occur and their strength is difficult.

• By studying areas of seismic activity, seismologists

have discovered some patterns in earthquakes that

allow them to make some general predictions.

Chapter F5




Earthquake Forecasting, continued

• Strength and Frequency Earthquakes vary in

strength. The strength of earthquakes is related to

how often they occur.

• This table shows more detail about the relationship.

Chapter F5





• Another method of forecasting an earthquake’s

strength, location, and frequency is the gap

hypothesis.

• The gap hypothesis is based on the idea that a

major earthquake is more likely to occur along the

part of an active fault where no earthquakes have

occurred for a certain period of time.

Chapter F5





• An area along a fault where relatively few earth-

quakes have occurred recently but where strong

earthquakes have occurred in the past is called a

seismic gap.

Chapter F5





• Using the Gap Hypothesis Not all seismologists

believe the gap hypothesis is an accurate method of

forecasting earthquakes.

• But some seismologists think the gap hypothesis

helped forecast the approximate location and strength

of the 1989 Loma Prieta earthquake in California.

Chapter F5




Gap Hypothesis and Seismic Gaps



the Esc key.

Visual Concept

Chapter F5

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Earthquakes and Buildings

• Earthquakes can easily topple buildings and destroy

homes. Today, older structures in seismically active

places, such as California, are being made more

earthquake resistant.

• Retrofitting is the name given to the process of

making older structure more earthquake resistant.

Chapter F5




Earthquakes and Buildings, continued

• A common way of retrofitting an older home is

to securely fasten it to its foundation.

• Steel is often used to strengthen buildings and

homes made of brick.

Chapter F5





• Earthquake-Resistant Buildings A lot has been

learned from building failure during earthquakes.

• With this knowledge, architects and engineers use

new technology to design and construct buildings

and bridges to better withstand earthquakes.

• The next slide shows some of the technology used

to make earthquake-resistant buildings.

Chapter F5





Chapter F5




Are You Prepared for an Earthquake?

• Before the Shaking Starts The first thing should

do safeguard your home against earthquakes.

• Place heavier objects on lower shelves so they do

not fall during an earthquake.

• Find safe places within each room of your home

and outside of your home.

• Make a plan with others to meet in a safe place

after the earthquake is over.

Chapter F5




Earthquake Preparations, continued

• When the Shaking Starts If you are indoors,

crouch or lie face down under a table or desk.

• If you are outside, cover your head with your hands

and lie face down away from buildings, power lines,

or trees.

• If you are in a car on an open road, you should stop

the car and remain inside.

Chapter F5




Earthquake Preparations, continued

• After the Shaking Stops Try to calm down and

get your bearings.

• Remove yourself from immediate danger, such as

downed power lines, broken glass, and fire hazards.

• Do not enter any damaged buildings unless you

are told it is safe by someone in authority.

• Beware that aftershocks may cause more

damage.

Chapter F5



Earthquakes

Concept Map

Use the terms below to complete the concept map on

the next slide.

seismograph

seismic waves

earthquakes

surface waves

body waves

S waves

Chapter F5



Earthquakes Chapter F5



End of Chapter F5 Show



Reading

Read each of the passages. Then, answer the

questions that follow each passage.

Standardized Test Preparation Chapter F5



Passage 1 At 5:04 p.m. on October 14, 1989, life in

California’s San Francisco Bay area seemed

normal. While 62,000 fans filled Candlestick Park to

watch the third game of the World Series, other

people were rushing home from a day’s work. By

5:05 p.m., the area had changed drastically. The

area was rocked by the 6.9 magnitude Loma Prieta

earthquake, which lasted 20 s and caused 68

deaths, 3,757 injuries, and the destruction of more

than 1,000 homes. Considering that the earthquake

was of such a high magnitude and that the

earthquake happened during rush hour, it’s amazing

that more people did not die.




1. In the passage, what does the word

drastically mean?

A continuously

B severely

C gradually

D not at all




2. Which of the following statements about the

Loma Prieta earthquake is false?

F The earthquake happened during rush hour.

G The earthquake destroyed more than 1,000

homes.

H The earthquake lasted for 1 min.

I The earthquake had a magnitude of 6.9.




3. Which of the following statements is a fact

in the passage?

A Thousands of people were killed in the

Loma Prieta earthquake.

B The Loma Prieta earthquake happened

during the morning rush hour.

C The Loma Prieta earthquake was a light to

moderate earthquake.

D The Loma Prieta earthquake occurred

during the 1989 World Series.




Passage 2 In the United States, seismologists use

the Modified Mercalli Intensity Scale to measure the

intensity of earthquakes. Japanese seismologists,

however, use the Shindo scale to measure

earthquake intensity. Earthquakes are assigned a

number between 1 and 7 on the scale. Shindo 1

indicates a slight earthquake. Such an earthquake is

felt by few people, usually people who are sitting.

Shindo 7 indicates a severe earthquake. An

earthquake that causes great destruction, such as

the earthquake that struck Kobe, Japan, in January

1995, would be classified as Shindo 7.




1. In the passage, what does the word

assigned mean?

A named

B voted

C given

D chosen




2. Which of the following statements about the

Shindo scale is true?

F The Shindo scale is used to measure earthquake

strength.

G The Shindo scale, which ranges from 1 to 7, is

used to rank earthquake intensity.

H The Shindo scale is the same as the Modified

Mercalli Intensity Scale.

I Seismologists all over the world use the Shindo

scale.




3. Which of the following is a fact in the passage?

A American seismologists use the Richter scale

instead of the Shindo scale.

B Japanese seismologists measure the intensity of

large earthquakes only.

C The Kobe earthquake was too destructive to be

given a Shindo number.

D Shindo 1 indicates a slight earthquake.




Interpreting Graphics

The graph below shows the change in temperature

during a chemical reaction. Use the graph below to

answer the questions that follow.




1. According to the seismogram, which waves travel

the fastest?

A P waves travel the fastest.

B S waves travel the fastest.

C P waves and S waves travel at the same speed.

D The graph does not show how fast P waves and S

waves travel.




2. What is the approximate difference in minutes

between the time the first P waves arrived at station B

and the time the first S waves arrived at station B?

F 22 1/2 min

G 10 1/2 min

H 8 min

I 3 min




3. Station A is

approximately how

much closer to the

epicenter than

station B is?

A 1,800 km

B 4,000 km

C 5,800 km

D 8,600 km




Math

Read each question, and choose the best answer.




1. If a seismic wave travels at a rate of 12 km/s,

how far will it travel away from the earthquake in

1 min?

A 7,200 km

B 720 km

C 72 km

D 7.2 km




1. If a seismic wave travels at a rate of 12

km/s, how far will it travel away from the

earthquake in 1 min?

A 7,200 km

B 720 km

C 72 km

D 7.2 km




2. If a P wave travels a distance of 70 km in

10 s, what is its speed?

F 700 km/s

G 70 km/s

H 7 km/s

I 0.7 km/s




3. Each time the magnitude of an earthquake

increases by 1 unit, the amount of energy

released is 31.7 times greater. How much

greater is the energy for a magnitude 7.0

earthquake than a magnitude 5.0 earthquake?

A 31,855 times as strong

B 63.4 times as strong

C 634 times as strong

D 1,005 times as strong




4. An approximate relationship between earthquake

magnitude and frequency is that when magnitude

increases by 1.0, 10 times fewer earthquakes occur.

Thus, if 150 earthquakes of magnitude 2.0 happen in

your area this year, about how many 4.0 magnitude

earthquakes will happen in your area this year?

F 50

G 10

H 2

I 0




5. If an average of 421,140 earthquakes occur

annually, what percentage of these earthquakes

are minor earthquakes if 49,000 minor

earthquakes occur annually?

A approximately .01%

B approximately .12%

C approximately 8.6%

D approximately 86%




Section 1 What Are Earthquakes? Chapter F5



Section 2 Earthquake Measurement Chapter F5



Section 3 Earthquakes and Society Chapter F5

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