Chapter 12 Section 2Earthquakes

Chapter 12 Section 2 – What You’ll Learn - page 363Before you read - write the reading’s objectives in this space:1 – _____________________________________________________________________________________________________________________________________________

2 – _____________________________________________________________________________________________________________________________________________________________________________________________

3- _______________________________________________________________________________________________________________________________________________________________________________________

Chapter 12 Section 2 – What You’ll Learn - page 363Before you read - write the reading’s objectives in this space:1 – Describe the causes and characteristics of earthquakes.

2 – Explain how seismic waves affect Earth’s surface.

3- Describe how seismic waves are used to infer Earth’s internal structure.

Define earthquake: __________________________________________________________________________Globally, how are most earthquakes distributed? _________________________________________________________________________________________________

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Define earthquake: An earthquake is any seismic vibration of Earth caused by the rapid release of energy. Globally, how are most earthquakes distributed? The zones coincide with the edges of lithospheric plates.

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Define focus (As pertaining to earthquakes):________________________________________________________

What kind of foci do divergent boundarieshave? _______________________________________

What kind of foci do convergent boundarieshave? _______________________________________________________________________________________________________________________________

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Define focus (As pertaining to earthquakes):The point of origin of an earthquake.

What kind of foci do divergent boundarieshave? Narrow bands of numerous shallow earthquakes

What kind of foci do convergent boundarieshave? Broad zones with the shallowest focal points are near the surface where boundaries converge. The deepest focal points lie under mountains or volcanoes that are created by the collisions.

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Explain deformation in reference to earthquakes:

_____________________________________________________________________________________________________________________________________________________________________

Name and define the four types of stress:

1._________________________________________

2._________________________________________

3.__________________________________________________________________________________

4._________________________________________

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Explain deformation in reference to earthquakes:

Stress is the force per unit area that acts on a material.

As plates shift a stress or strain is placed on the plate. Brittle, ridged rocky material shows very little sign of deformation but then will suddenly break.

Name and define the four types of stress:

1.Compressive – material is squeezed or shortened

2.Tensional – material is stretched or lengthened

3.Shear – material is moved in opposite directions along a plane

4.Torsion – material is twisted

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Save for class work - Four Types of Stress Mini-Lab Answers:

1. With palms facing down at all times and your hands in contact with each other,clasp a large bar of taffy with both hands. First, push one hand forward 2 cm while simultaneously pulling the other backward 2 cm. Return your hands to the original position.Type of stress - ______________________________________________Kind of deformation - __________________________________________2. Still holding your hands in contact, twist your hands in opposite directions and return them to the original position. Type of stress - _______________________________________________Kind of deformation - __________________________________________3. Next move your hands about 4 cm apart. Type of stress - _______________________________________________Kind of deformation - __________________________________________4. Finally push your hands back together to the original position.Type of stress - _______________________________________________Kind of deformation - __________________________________________

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Four Types of Stress Mini-Lab Answers:

1. With palms facing down at all times and your hands in contact with each other,clasp a large bar of taffy with both hands. First, push one hand forward 2 cm while simultaneously pulling the other backward 2 cm. Return your hands to the original position.Type of stress - shearKind of deformation – shaved off, split, sliced, ground up, scraped, peeled, abrasion2. Still holding your hands in contact, twist your hands in opposite directions and return them to the original position. Type of stress - torsionKind of deformation – twisted, wrenched, wound-up, coiled, curled3. Next move your hands about 4 cm apart. Type of stress - tensionKind of deformation – stretched, pulled apart, broken, pulled thin4. Finally push your hands back together to the original position.Type of stress - compressionKind of deformation – smooshed, squeezed, folded, compressed, crushed

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Define elastic deformation:___________________________________________________________________________________________________________________________________Define plastic deformation:____________________________________________________________________________________________________________________________________________________________

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Define elastic deformation: Elastic deformation occurs when a material deforms as a stress is applied, but returns to its original shape when the stress is removed.

Define plastic deformation: Plastic deformation occurs when a material deforms, or changes shape, as a stress is applied and remains in the new shape when the stress is released.

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Energy Release:When this strain energy is released suddenly, it causes rock to lurch to a new position.

Define fault: _______________________________________________The sudden energy release that goes with fault movement is called ________________________

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Energy Release:When this strain energy is released suddenly, it causes rock to lurch to a new position.

Define fault: A crack along which movement has taken place.The sudden energy release that goes with fault movement is called elastic rebound.

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Recall an earthquakes focus:_____________________________________________________________________What is an earthquake’s epicenter? ____________________________________________________________________________________ 7

Recall an earthquakes focus:The point of origin of an earthquake.

What is an earthquake’s epicenter? The point on Earth’s surface directly above the focus

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What are Primary waves (P-waves)? _______________________________________________________________________________________________________Recall in the waves section that if you attach the tie to one on the rungs the particles do not change location.

•P-waves travel through all kinds of matter.8

What are Primary waves (P-waves)? P-waves are compressional waves. This causes particles in a material to undergo a push-pull type motion. Recall in the waves section that if you attach the tie to one on the rungs the particles do not change location.

•P-waves travel through all kinds of matter.8

What are secondary waves (s-waves or shear waves)? ______________________________________________________________________________________________________________________________Remember: Transverse waves cause particles to move perpendicular to the direction of wave travel.

• S-waves can only travel through solids.

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What are secondary waves (s-waves or shear waves)? Are transverse waves, sometimes called shear waves, because of the relative motion of particles as energy is transferred. Remember: Transverse waves cause particles to move perpendicular to the direction of wave travel.

• S-waves can only travel through solids.

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Surface waves move in a more complex manner.

They can exhibit an up and down rolling motion, and also a side-to-side motion that parallels Earth’s surface.

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Earthquake Measurement

• The Modified Mercalli scale ranks earthquakes in a range from I-XII, XII being the worst and uses eyewitness observation and post-earthquake assessments to assign an intensity value.

Earthquake Measurement

• Richter magnitude is intended to give a measure of the energy released during the earthquake.

• The Richter magnitude scale uses the amplitude of the largest earthquake wave.

EQ as seen by a surveillance cameraClick here

What increases earthquake damage and loss of life?

________________________________________________________________________________Earthquake Proofing -Although no building can be made entirely earthquake proof, scientists and engineers are finding ways to reduce the damage to structures during mild or moderate earthquakes.

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What increases earthquake damage and loss of life? Research has shown that poor building methods are the largest contributors to earthquake damage and loss of life.

Earthquake Proofing -Although no building can be made entirely earthquake proof, scientists and engineers are finding ways to reduce the damage to structures during mild or moderate earthquakes.

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Question 1Which of the following is NOT a type of stress in rock?

A. compressionB. epicenterC. shearingD. tension

Section CheckSection Check

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Question 1Which of the following is NOT a type of stress in rock?

A. compressionB. epicenterC. shearingD. tension

Section CheckSection Check

AnswerThe answer is B. The epicenter is the point on Earth’s surface located directly above the earthquake’s center.

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Question 2Where do P- and S-waves occur in relation to surface waves?

Section CheckSection Check

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22Question 2

Where do P- and S-waves occur in relation to surface waves?

AnswerSeismic waves travel away from the epicenter in all directions. P-waves travel the fastest through rock material. S-waves move through the rock and cause particles to vibrate. Both P- and S-waves travel through the Earth’s interior while surface waves move along Earth’s surface.

Section CheckSection Check

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Question 3Why is it difficult to predict earthquakes?

Section CheckSection Check

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Question 3Why is it difficult to predict earthquakes?

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AnswerGeologists can monitor changes in Earth that are associated with earthquakes. Measuring devices have been developed to assess changes in groundwater level and rock layers; however, no single change in Earth occurs for all earthquakes.

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