Lessons 1-4Lessons 1-4

Lesson 1:

What are earthquakes and where do they

occur

Where do Earthquakes Occur?

• Earthquakes can occur near the Earth’s surface or far below the surface.

• Most earthquakes occur at plate boundaries, but some happen at faults located in the middle of tectonic plates.

http://www.dosecc.org/html/volcanic_monitoring.html

PLATE BOUNDARIES

Earthquake Locations Around the World

What Causes Earthquakes?• Earthquakes are caused by movement along

faults.• When stress is placed on rocks it deforms, or

changes.• This is called Elastic Deformation (remember

faults and folds, tension and compression)• Rock is stretched and bent until it can no longer

take the stress.• When enough stress builds up in the rock it, it

slips and energy is released.• The rock then returns to its original shape. This

is called Elastic Rebound. Think of a rubber band, you can only stretch it so far until it breaks and return to its original shape.

• This energy is felt as an earthquake.

ELASTIC REBOUND

Elastic

Earthquakes in Alabama??Earthquakes in Alabama??

Do we live near a plate boundary?Do we live near a plate boundary?

Do we live near a fault?Do we live near a fault?

The New Madrid FaultThe New Madrid Fault If there is no plate boundary in the middle of the If there is no plate boundary in the middle of the

United States, why did these earthquakes take place? United States, why did these earthquakes take place? Geologists are beginning to understand the answer. Geologists are beginning to understand the answer.

The New Madrid Fault Zone is part of an The New Madrid Fault Zone is part of an ancientancient plate plate boundary. In this area, the North American Plate tried boundary. In this area, the North American Plate tried to form a divergent plate boundary about 500 million to form a divergent plate boundary about 500 million years ago. The splitting stopped before new plates years ago. The splitting stopped before new plates could form. The faults in the New Madrid Zone are could form. The faults in the New Madrid Zone are remnants of this old event. Earthquakes occur because remnants of this old event. Earthquakes occur because the North American Plate is still "settling down". The the North American Plate is still "settling down". The faults in the New Madrid Zone do not reach the Earth’s faults in the New Madrid Zone do not reach the Earth’s surface. They are buried beneath thousands of feet of surface. They are buried beneath thousands of feet of rock and sediment deposited by the Mississippi River. rock and sediment deposited by the Mississippi River. Geologists have located them by looking at the Geologists have located them by looking at the patterns of earthquakes in the zone. patterns of earthquakes in the zone.

Several of the Several of the largest earthquakes largest earthquakes ever recorded in the ever recorded in the

United States United States occurred in the occurred in the

Midwest, far from Midwest, far from any plate boundary. any plate boundary. These earthquakes These earthquakes

took place in an area took place in an area called the New called the New

Madrid Fault Zone, Madrid Fault Zone, named after the named after the

town of New Madrid, town of New Madrid, Missouri.Missouri.

New Madrid FaultNew Madrid Fault

Over a three-month period in the Over a three-month period in the winter of 1811 to 1812, the New winter of 1811 to 1812, the New Madrid Fault Zone was struck by Madrid Fault Zone was struck by three huge earthquakes estimated to three huge earthquakes estimated to be greater than magnitude 8.0 be greater than magnitude 8.0

The New Madrid Fault is what causes The New Madrid Fault is what causes Alabama to experience earthquakes.Alabama to experience earthquakes.

The map shows The map shows the earthquakes the earthquakes recorded in recorded in Alabama since Alabama since 1886. 1886.

The last earthquake to occur in Alabama was on July 27, of this year. It measured a 2.6 on the Richter scale.

This was not a very strong earthquake, but it was recorded by a seismograph, an instrument used to measure earthquakes.

Lesson 2

3 Types of Faults associated with Earthquakes

PLATE MOTION FAULT TYPE

Transform Strike –Slip Fault

Convergent Reverse Fault

Divergent Normal Fault

Strike-Slip Fault occurs at a Transform Boundary

Reverse Fault occurs at a Convergent Boundary

Normal Faults occur at Divergent Boundaries

Chapter 8: Sections 1: Earthquakes and Faults: Organizer

PLATE MOTION FAULT TYPETransform Strike –Slip Fault

Convergent Reverse Fault

Divergent Normal Fault

Plates move past each other

Plates move together

Plates move apart

Fault blocks move past each other

Fault blocks move together

Fault blocks move apart

Lesson 3Lesson 3

How do Earthquake Waves Travel?How do Earthquake Waves Travel?

Energy releasedEnergy released from moving from moving plates and faultsplates and faults travels travels through through the Earth the Earth as wavesas waves..

These waves are These waves are called seismic called seismic waveswaves..

Types of Seismic WavesTypes of Seismic Waves

1. 1. BODY WAVESBODY WAVES:: Seismic waves that travel Seismic waves that travel through the Earth.through the Earth.

2. 2. SURFACE WAVESSURFACE WAVES:: Seismic waves that travel Seismic waves that travel along the surface.along the surface.

WAVES TRAVEL:WAVES TRAVEL:

1.1.At different speedsAt different speeds and and

2 2 In different waysIn different ways

Depending on what kind of material Depending on what kind of material they are moving through.they are moving through.

Body Waves• There are two types of body

waves:– P-waves– S-waves

P-waves P-waves are pressure waves. P-waves travel through solid, liquids and gases. P-waves are the fastest waves. P-waves are the first waves to be detected and the first waves to

arrive. P-waves are also called primary waves because they arrive first. P-waves cause rock to squeeze and stretch. Imagine a slinky!

The area of the Earth that does not receive seismic energy is called the shadow zone.

1.P-Waves

2. S-waves S-waves are the second fastest waves. S-waves are also called secondary waves

because they arrive second. S-waves are slower than P-waves. S-waves move rock from side to side.

S-waves can’t travel through parts of the Earth that are completely liquid.

S-Waves

3. Surface Waves• Surface waves move along the surface of

the Earth.

• Surface waves can move up, down and around or side to side.

• Surface waves move the slowest and cause the most destruction.

Surface Waves

Seismic Wave Arrival• First- P-waves

• Second- S-waves

• Third- Surface Waves

Shadow Zone

The shadow zone results from S waves being stopped entirely by the liquid core and P waves being bent (refracted) by the liquid core.

Moho Zone The Moho is the boundary between the crust and the mantle in the

earth. This is a depth where seismic waves change velocity, or speed. They tend to increase at the location.

Quiz• 1. Most Earthquakes occur along ________________.• 2. The first seismic waves to arrive are______________.• 3. The second seismic waves to arrive are

_____________.• 4. The last seismic waves to arrive are_______________.• 5. Which seismic waves travel the fastest?___________• 6. Which type of seismic wave can move through a

solid, liquid or a gas?________________• 7. Which seismic wave cannot travel through material

that is completely liquid?______________• 8. Which seismic waves are the slowest and the most

destructive?_______________

Earthquake Earthquake MeasurementMeasurementEarthquake Earthquake

MeasurementMeasurement

Lesson 4

Seismograph• A seismograph is an instrument used by scientists to measure

earthquakes.• Seismologists who study earthquakes can determine when an

earthquake started by noting the arrival times of P-waves and S-waves.

• A seismograph records vibrations in the Earth and determines the strength and location of an earthquake.

Ancient Chinese Seismograph. The ball would drop from the dragon to the frog. It told the people which direction the earthquake come from.

SeismogramsSeismograms

Time in Minutes0 1 2 3 4 5 6 7 8

1. How many minutes did it take for the

P-Waves to arrive?

2. How many minutes did it take for the

S-waves to arrive?

3. How long did the surface waves last?

Epicenter• The epicenter is the point on the

Earth’s surface directly above an earthquake’s starting point.

Focus• The focus is the point inside the

Earth where the earthquake begins.

• The epicenter is located directly above the focus.

Measuring Earthquakes• There are two major ways

earthquakes are measured:

1. Richter Scale

2. Mercalli Scale

Richter Scale/Measures MagnitudeRichter Scale/Measures Magnitude The The Richter ScaleRichter Scale measures magnitude.measures magnitude. The The measurements are given in numbersmeasurements are given in numbers.. Measures the energy released by an earthquakeMeasures the energy released by an earthquake

Earthquake Severity-Energy released by an earthquake.Earthquake Severity-Energy released by an earthquake. Richter Earthquake Magnitudes EffectsRichter Earthquake Magnitudes Effects

Less than 3.5Less than 3.5 Generally not felt, but recorded. Generally not felt, but recorded. 3.5-5.43.5-5.4 Often felt, but rarely causes damage. Often felt, but rarely causes damage. Under 6.0Under 6.0 At most slight damage to well-designed buildings. Can At most slight damage to well-designed buildings. Can

cause major damage to poorly constructed buildings over small cause major damage to poorly constructed buildings over small regions.regions.

6.1-6.96.1-6.9 Can be destructive in areas up to about 100 kilometers Can be destructive in areas up to about 100 kilometers across where people live. across where people live.

7.0-7.97.0-7.9 Major earthquake. Can cause serious damage over larger Major earthquake. Can cause serious damage over larger areas. areas.

8 or greater8 or greater Great earthquake. Can cause serious damage in areas Great earthquake. Can cause serious damage in areas several hundred kilometers across. several hundred kilometers across.

Mercalli Scale/Measures Mercalli Scale/Measures IntensityIntensity In seismology a scale of In seismology a scale of seismic intensityseismic intensity is a way of measuring or rating the is a way of measuring or rating the effects effects of an of an

earthquake at different sites.earthquake at different sites. The Modified Mercalli Intensity ScaleThe Modified Mercalli Intensity Scale is commonly used in the United States by is commonly used in the United States by

seismologists seeking information on the severity of earthquake effects. Intensity ratings seismologists seeking information on the severity of earthquake effects. Intensity ratings are are expressed as Roman numeralsexpressed as Roman numerals between I at the low end and XII at the high end. between I at the low end and XII at the high end.

I. I. People do not feel any Earth movement.People do not feel any Earth movement.II.II. A few people might notice movement if they A few people might notice movement if they

are at rest and/or on the upper floors of tall are at rest and/or on the upper floors of tall buildings.buildings.

III.III. Many people indoors feel movement. Many people indoors feel movement. Hanging objects swing back and forth. People Hanging objects swing back and forth. People outdoors might not realize that an earthquake outdoors might not realize that an earthquake is occurring. is occurring.

IV.IV. Most people indoors feel movement. Hanging Most people indoors feel movement. Hanging objects swing. Dishes, windows, and doors objects swing. Dishes, windows, and doors rattle. A few people outdoors may feel rattle. A few people outdoors may feel movement. Parked cars rock.movement. Parked cars rock.

V.V. Almost everyone feels movement. Doors swing Almost everyone feels movement. Doors swing open or close. Dishes are broken. Pictures on open or close. Dishes are broken. Pictures on the wall move. Small objects move or are the wall move. Small objects move or are turned over. turned over.

VI.VI. Everyone feels movement. People have Everyone feels movement. People have trouble walking. Objects fall from shelves. trouble walking. Objects fall from shelves. Pictures fall off walls. Furniture moves. Plaster Pictures fall off walls. Furniture moves. Plaster in walls might crack. Trees and bushes shake. in walls might crack. Trees and bushes shake.

VII. People have difficulty standing. Drivers feel their cars shaking. Some furniture breaks. Loose bricks fall from buildings. Damage is slight to moderate in well-built buildings; considerable in poorly built buildings. VIII. Drivers have trouble steering. Houses that are not bolted down might shift on their foundations. Tall structures such as towers and chimneys might twist and fall. Well-built buildings suffer slight damage. Poorly built structures suffer severe damage. Tree branches break. Hillsides might crack if the ground is wet. IX. Well-built buildings suffer considerable damage. Houses that are not bolted down move off their foundations. Some underground pipes are broken. The ground cracks. X. Most buildings and their foundations are destroyed. Some bridges are destroyed. Dams are seriously damaged. Large landslides occur. Water is thrown on the banks of canals, rivers, lakes. The ground cracks in large areas. Railroad tracks are bent slightly. XI. Most buildings collapse. Some bridges are destroyed. Large cracks appear in the ground.. Railroad tracks are badly bent. XII. Almost everything is destroyed. Objects are thrown into the air. The ground moves in waves or ripples. Large amounts of rock may move. As you can see from the list above, rating the Intensity of an earthquake's effects does not require any instrumental measurements. Thus seismologists can use newspaper accounts, diaries, and other historical records to make intensity ratings of past earthquakes.

6.7

1. What was the magnitude of the Hawaii earthquake?

2. Where was the intensity the greatest?

3.According to the Mercalli Scale on what island did the most damage likely occur?

Hawaii

Maui V-VI

Oahu

VI VVII

IV

Mercalli Intensity ScaleMercalli Intensity Scale

1. What is the intensity at Monterey?

2. What is the intensity at the epicenter?

3. What is the intensity at San Jose?

4. What is the intensity at Santa Cruz?

5. What is the intensity at Smith?

Smith

Largest Earthquake in Alabama: 1916 South of Birmingham, in Irondale

5.1 on the Richter Scale

VII (7) on Mercalli Scale

Earthquakes in Alabama?