Lesson One Essential Question Where do earthquakes take place? What causes earthquakes? What are three different types of faults that occur at plate boundaries? How does energy from earthquakes travels through the Earth? Lesson One Terms Seismology Deformation Elastic rebound Seismic waves P waves S waves Lesson One Earthquakes What Are Earthquakes? There is more to earthquakes than just the shaking of the ground. An entire branch of Earth science, called, is devoted to the study of earthquakes. are complex, and they present many questions for, the scientists who study earthquakes. Where Do Earthquakes Occur? Most earthquakes take place near the edges Tectonic plates move in different and at different. As a result, numerous features called faults exist in the Earth s crust. A is a break in the Earth s crust along which blocks of the crust slide relative to one another. occur along faults because of this sliding. What Causes Earthquakes? As tectonic plates increases along faults near the plates edges. In response to this stress, rock in the plates. is the change in the shape of rock in response to the stress of bending, tilting, and breaking of the Earth s crust. Rock along a fault deforms in mainly two ways. Rock deforms in a, like a piece of molded clay, or in an, like a rubber band. does not lead to earthquakes. does. Like a rubber band, rock can be stretched only so far before it breaks. 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. 1
During elastic rebound, energy is. Some of this energy travels as seismic waves, which cause an. Faults at Tectonic Plate Boundaries A specific type of takes place at different tectonic plate boundaries. Each type of creates a particular kind of that can produce earthquakes. occurs where two plates slip past each other, creating. Blocks of crust slide horizontally past each other. occurs where two plates push together, Lesson One Evaluation 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. creating. Blocks of crust that are pushed together slide along reverse faults. occurs where two plates pull away from each other, creating. Blocks of crust that are pulled away from each other slide along normal faults. 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. How Do Earthquake Waves Travel? Waves of energy that travel through the Earth away from an earthquake are called. First Seismograph by Chinese Types of earthquake waves 1. 2. 3. 2
Seismic Waves: Surface Waves Seismic waves that travel through Earth s interior are called. There are two types of body waves: P waves and S waves. A. P waves are seismic waves that cause particles of rock to move in a back-andforth direction. Lesson Two Essential Question How earthquakes are detected? How does one locate an earthquake s epicenter? How is the strength of an earthquake is measured? How is the intensity of an earthquake is measured? Lesson Two Terms Seismograph Seismogram Epicenter Focus Lesson Two Evaluation With a classmate: Explain how earthquakes are detected. Describe how to locate an earthquake s epicenter. With a classmate: Explain how the strength of an 1. (P) waves 2. (compressional) motion 3. Travel through 4. Fastest B. S waves are seismic waves that cause particles of rock to move in a side-toside direction. 1. (S) waves 2. " " motion 3. Travel only through 4. velocity than P waves C. waves a. Complex motion b. Slowest End of Lesson One Lesson Two Locating Earthquakes Scientists use seismographs to study earthquakes. A 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, a tracing of the earthquake s motion Determining Time and Location of Earthquakes 3
earthquake is measured. Explain how the intensity of an earthquake is measured. Lesson Three Essential Questions How is earthquakehazard level determined? What are the methods of earthquake forecasting. What are five ways to safeguard buildings against earthquakes? What are the earthquake safety procedures? Lesson Three Terms Gap Hypothesis Seismic Gap Hazard level map Retrofitting Earth-quake resistant Liquefaction Aftershock Tsunami Base-isolation building are used to find an earthquake s epicenter. An is the point on the Earth s surface directly above an earthquake s starting point. A 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. The S-P Time Method is perhaps the simplest method by which seismologists find an earthquake s epicenter. The epicenter is located using three or more seismograph Measuring Earthquake Strength and Intensity 1. The 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. 2. scale a. Widely accepted to measure very large earthquakes b.. Only scale that shows size of large earthquakes c. Measures the size of the rupture and the amount of displacement that occurs along a fault zone d. Field studies are done and seismographic studies are done. 3. 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 Intensity Scale to measure earthquake intensity. This is a numerical scale that uses Roman numerals from I to XII to describe earthquake intensity levels. In the Modified 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. End of Lesson Two 4
Lesson Three Earthquakes and Society Earthquake Hazard Earthquake 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. IV. Earthquake Destruction A. Factors that determine structural damage 1.Intensity of the earthquake 2.Duration of the vibrations 3. Nature of the material upon which the structure rests 4. The design of the structure B. Causes of Earthquake Damage 1. 2. 3. 4. 5. 6. 7. Direct a. destroys buildings, bridges break, gas and water lines break, dams break, rockslides occur 2. Secondary Effects a. of the ground Saturated material turns fluid Underground objects may float to surface. Landslides and mudflows because the shaking causes the soil to flow. b. - caused by gas line breaks and electrical shorts. 80% of the damage is caused by fire c. - earth movement near ocean floor creates giant sea waves, called seismic sea waves, cause total destruction of areas. 5
C. Reducing Earthquake Damage The greater the seismic activity, the higher the earthquake-hazard level. a. Geologists can determine earthquake risk by locating where faults active and where past earthquakes have occurred. Earthquake-Hazard Level 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. Earthquakes vary in strength. The strength of earthquakes is related to how often they occur. Another method of forecasting an earthquake s strength, location, and frequency is the. The 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. 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. Using the 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. Earthquakes and Buildings Earthquakes can easily topple and destroy homes. Today, older structures in seismically active places, such as California, are being made more earthquake resistant. is the name given to the process of making older structure more earthquake resistant. A common way of an older home is to securely fasten it to its foundation. Steel is often used to strengthen buildings and homes made of brick. 6
Buildings A lot has been learned from building during earthquakes. With this knowledge, architects and engineers use new technology to design and construct buildings and bridges to better withstand earthquakes. Some of the technology used to make earthquake-resistant buildings. 2. Build buildings a. New buildings must be stronger and more flexible Make older buildings safer Strengthen building Keep objects from tipping over 1) are reinforced with cross bracing. 2) Build on pads to absorb the energy (Base isolators) Are You Prepared for an Earthquake? Before the Shaking Starts The first thing should do safeguard your home against earthquakes. Place on lower shelves so they do not fall during an earthquake. within each room of your home and outside of your home. Make a plan with others to after the earthquake is over. When the Shaking Starts If you are indoors, crouch or 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 and remain inside. 7
Lesson Three Evaluation With a classmate: Explain how earthquake-hazard level is determined. Compare methods of earthquake forecasting. With a Classmate: Describe five ways to safeguard buildings against earthquakes. Outline earthquake safety procedures. Describe the types of damage caused by earthquakes After the Shaking Stops Try to Remove yourself from immediate danger, such as any damaged buildings unless you are told it is safe by someone in authority. Beware that cause more damage. Quake Challenge 240-241 Holt Textbook. End of Lesson Three End Of Chapter 8 Earthquakes 8
Lesson One Essential Question Where do earthquakes take place? What causes earthquakes? What are three different types of faults that occur at plate boundaries? How does energy from earthquakes travels through the Earth? Lesson One Terms Seismology Deformation Elastic rebound Seismic waves P waves S waves Lesson One Earthquakes 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. Where Do Earthquakes Occur? Most earthquakes take place near the edges of tectonic plates 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. 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. 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. Elastic rebound 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. 9
During elastic rebound, energy is released. Some of this energy travels as seismic waves, which cause an earthquake. 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. Transform motion occurs where two plates slip past each other, creating strike-slip faults. Blocks of crust slide horizontally past each other. Convergent motion occurs where two plates push together, Lesson One Evaluation 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. creating reverse faults. Blocks of crust that are pushed together slide along reverse faults. 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. 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. How Do Earthquake Waves Travel? Waves of energy that travel through the Earth away from an earthquake are called seismic waves. First Seismograph by Chinese Types of earthquake waves 4. Primary (P) waves 5. Secondary (S) waves 6. Surface 10
Seismic Waves: Surface Waves Seismic waves that travel through Earth s interior are called body waves. There are two types of body waves: P waves and S waves. D. P waves are seismic waves that cause particles of rock to move in a back-andforth direction. 1. Primary (P) waves Lesson Two Essential Question How earthquakes are detected? How does one locate an earthquake s epicenter? How is the strength of an earthquake is measured? How is the intensity of an earthquake is measured? Lesson Two Terms Seismograph Seismogram Epicenter Focus Lesson Two Evaluation With a classmate: Explain how earthquakes are detected. Describe how to locate an earthquake s epicenter. With a classmate: 2. Push-pull (compressional) motion 3. Travel through solids, liquids, and gases 4. Fastest E. S waves are seismic waves that cause particles of rock to move in a side-toside direction. 5. Secondary (S) waves 6. "Shake" motion 7. Travel only through solids 8. Slower velocity than P waves F. Surface waves c. Complex motion d. Slowest e. Cause destruction End of Lesson One Lesson Two 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. Determining Time and Location of Earthquakes Seismograms are 11
Explain how the strength of an earthquake is measured. Explain how the intensity of an earthquake is measured. Lesson Three Essential Questions How is earthquakehazard level determined? What are the methods of earthquake forecasting. What are five ways to safeguard buildings against earthquakes? What are the earthquake safety procedures? Lesson Three Terms Gap Hypothesis Seismic Gap Hazard level map Retrofitting Earth-quake resistant Liquefaction Aftershock Tsunami Base-isolation building used to find an earthquake s epicenter. An epicenter is the point on the Earth s surface directly above an earthquake s starting point. 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. The S-P Time Method is perhaps the simplest method by which seismologists find an earthquake s epicenter. The epicenter is located using three or more seismograph Measuring Earthquake Strength and Intensity 1. 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. 2. Moment magnitude scale a. Widely accepted to measure very large earthquakes b.. Only scale that shows size of large earthquakes c. Measures the size of the rupture and the amount of displacement that occurs along a fault zone d. Field studies are done and seismographic studies are done. 3. 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. 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. End of Lesson Two 12
Lesson Three Earthquakes and Society 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. IV. Earthquake Destruction A. Factors that determine structural damage 1.Intensity of the earthquake 2.Duration of the vibrations 3. Nature of the material upon which the structure rests 4. The design of the structure B. Causes of Earthquake Damage 8. Shaking 9. Liquefaction 10. Landslides 11. Fires 12. Mudflows 13. Tsunamis 14. Direct a. Shaking destroys buildings, bridges break, gas and water lines break, dams break, rockslides occur 2. Secondary Effects a. Liquefaction of the ground Saturated material turns fluid Underground objects may float to surface. Landslides and mudflows because the shaking causes the soil to flow. b. Fires- caused by gas line breaks and electrical shorts. 80% of the damage is caused by fire c. Tsunamis- earth movement near ocean floor creates giant sea waves, called seismic sea waves, cause total destruction of areas. 13
C. Reducing Earthquake Damage The greater the seismic activity, the higher the earthquake-hazard level. a. Geologists can determine earthquake risk by locating where faults active and where past earthquakes have occurred. Earthquake-Hazard Level 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. Strength and Frequency Earthquakes vary in strength. The strength of earthquakes is related to how often they occur. 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. 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. 14 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. 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. 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.
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. Some of the technology used to make earthquake-resistant buildings. 2. Build earthquake resistant buildings a. New buildings must be stronger and more flexible Make older buildings safer Strengthen building Keep objects from tipping over 1)Steel frames are reinforced with cross bracing. 2) Build on large rubber pads to absorb the energy (Base isolators) 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. 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. 15
Lesson Three Evaluation With a classmate: Explain how earthquake-hazard level is determined. Compare methods of earthquake forecasting. With a Classmate: Describe five ways to safeguard buildings against earthquakes. Outline earthquake safety procedures. Describe the types of damage caused by earthquakes 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. Quake Challenge 240-241 Holt Textbook. End of Lesson Three End Of Chapter 8 Earthquakes 16
Seismology Deformation Elastic rebound 17
Seismic waves P waves S waves 18
Seismograph Seismogram Epicenter 19
Focus Gap Seismic Gap Hazard level map 20
Retrofitting Earth-quake resistant Liquefaction 21
Aftershock Tsunami Base-isolation 22