Earth Science Textbook Chapter 5 Earthquakes

Chapter Plate tectonics um of Earth nurture and or I events . As a bath for th I can not Students know that earthquakes are sudden motions alon breaks in the crust a that volcanoes and fissures are locations where magma reaches the surface . Students know major geologic events , such as earthquakes . volcanic eruptions . and building , result trom mate motions . Students know how to features of geology including faults , and volcanoes ) in terms of plate ! know that the ( ol an earthquake on any region vary , on the sire oi the earthquake . the distance oi the reg on from the ter . the local geology , and the type of construction in the region . Topography reshaped by the weathering ! rock and soil and by the trans and deposition of sediment . As a Int this concept Students know earthquakes . volcanic eruptions . and floods change human and habitats . An earthquake destroyed this ( in . in 1989 ,

' mum and nut Earthquakes ' BIG Idea . How do plate motions affect Earth crust ?

Check What You Know Imagine grasping a paper towel in both hands and slowly pulling your hands apart . At first , you see the paper towel stretch . Then , suddenly , it tears ! How is the tearing paper towel similar to an earthquake ?

How is it different ?

Chapter 159 The images shown here represent some of the key terms in this chapter . You can use this vocabulary to help you understand the meaning of same key terms in this chapter . Academic Words academic words are words that are used frequently in academic reading , writing , and discussions . Word I I , category A class or The books on the shelf ( car uh ee ) group of things are separated into two 134 and sciences construct The goal was to construct a ( Run ) building that would stand up 205 during an earthquake . expend To spread out The experiment ( into a scientific investigation . method , A way or Writing a letter and sending ( ud ) system at doing an email are two of 186 things sharing information . Apply It ! From the list above , choose the word that best completes the sentence . A balloon will until it breaks . The work crew will the bridge to be safe during an earthquake .

Chapter Vocabulary Section , stress tension shearing normal fault hanging wall footwall reverse fault fault plateau Section earthquake focus epicenter wave wave surface wave scale magnitude sale seismograph moment magnitude scale Section seismogram friction liquefaction aftershock tsunami building If ' Build Vocabulary Online Use !

Identify Main Idea The main idea in a paragraph is the most important , or biggest . idea . Sometimes the main idea is stated directly . At other times you must identify the main idea yourself . Here are some tips . Look at the heading or subheading . Read the first and last tew sentences in the paragraph . Identity the main idea of the paragraph . Identify a few important details about the topic . Read the paragraph below , Then identify the main idea . In your notebook , write the main idea in the first box and a few supporting details and examples in the boxes under it . House There are ways to an occurs . Supporting brick with metal brackets adds strength . Fastening and to wood in the wall keeps them from ' illing . Adding plywood boards to walls strengthens . Supporting brick ( with metal brackets adds strength . Apply It ! Look for main ideas and supporting details in paragraphs in this chapter .

Standards Investigation I Design and Build an House Earthquakes are proof that our planet is subject to great forces from within . Earthquakes remind us that we live on the moving pieces of Earth crust . In this chapter you will design a structure that can withstand earthquakes . Your Goal To design . build , and test a model structure that is earthquake resistant Your structure must be made of materials that have been approved by your teacher be built to specifications agreed on by your class be able to withstand several earthquakes of increasing intensity be built following the safety guidelines in Appendix A , Plan It ! Before you design your model , find out how earthquakes damage structures such as homes , office buildings , and highways . Preview the chapter to find out how engineers design structures to withstand . Then choose materials for your structure and sketch your design . When your teacher has approved your design . build and test your structure .

Section Forces in Earth Crust lE Students know major geo logic events . such as earthquakes . volcanic eruptions . and mountain building . result from plate motions . Students know how to explain major features of geology ( including mountains . and volcanoes ) in terms of plate tectonics How does stress in the crust change Earth surface ?

Where are usually , and why do they form ?

What land result Item the forces at plate movement ?

Key Terms I stress I tension ' I shearing I normal I hanging wall I I reverse fault I I plateau Effects of Stress Powerful forces in Earth crust caused the ground beneath this athletic in Taiwan to change its shape 174 Standards How Does Stress Affect Crust ?

Put on your goggles . Holding a popsicle stick at both ends . slowly bend it into an arch , Release the pressure on the popsicle stick and observe what happens . Repeat Steps and . This time . however , keep bending the ends of the popsicle stick toward each other . What happens to the wood ?

Think It Over Think of the stick as a model for part of Earth crust . What do you think might eventually happen as the forces of plate movement bend the crust ?

The of Earth plates creates great forces that or pull the rock in the trust as if it wen candy bar . These forces are of stress . a force that acts an area of rock to change its shape volume . A rock is the ' the ruck takes up . Because stress is 21 . it adds energy to the rock . The energy is stored in the rock until the rock changes shape or breaks . If you try to break caramel candy bar in two . it may only and stretch at a candy bar . many types of rock can or fold . But a certain limit . even these rocks will break .

Compression pushes ruck together . Tension Shearing Tension stretches rock . Shearing can cause masses of rock to slip . Types of Stress Three different kinds of stress can occur in the . pus . putt af , compression . and shearing . Tension . compression . and the rocks in Earth crust . shearing work over millions of years to change the shape ' if mi and volume of rock . Stress causes some rocks to become ma ) and snap . Other rocks slowly . like road tar softened by the sun . Figure shows how ' all the crust . Most changes in the crust so slowly that they can not be observed . But could speed up soa billion years passed by in minutes . you would see the crust bond . stretch . break . till . fold . and slide . The slow shift of Earth . The type of stress called tension pulls on the crust . stretching rock so that it becomes thinner in the middle . The of tension on rock is somewhat like pulling a piece of warm bubble gum . Tension occurs where two plates are moving apart . Compression A type of stress called compression rock until it folds or . plate pushing against another can compress rock like a giant trash Shearing Stress that pushes a mass of rock in two opposite directions is called shearing . Shearing can cause rock to and slip apart or to change its shape . are ) How does shearing alert in Earth crust ?

115 From Kinds of Faults There are three main kinds of faults normal faults , reverse faults . and faults . Inferring Which half of a normal fault would you expect to form the floor of a valley ?

Why ?

Force deforming the crust Movement along A the bolt Normal fault Kinds of Faults When enough stress builds up in rock , the rock breaks , creating a fault . Recall that a fault is a break in the rock of the crust whene rock surfaces slip past each other . The rocks on both sides of a fault can move up or down or sideways . Most faults occur along plate boundaries , where the forte of plate motion push or pull the crust so much that the crust breaks . There are three types of faults . reverse faults , and faults . Normal Fault Tension in Earth crust pulls rock apart . causing normal faults . In a normal fault . the fault is at an angle . so one block of rock lies above the other block of rock . The block of rock that lies above is called the hanging wall . The rock that ( below is called the . Look at Figure to see how the hanging wall lies above the footwall . When movement occurs along a normal fault . the hanging wall slips downward . Normal faults occur where plates diverge . or pull apart . For example . normal faults are found along the Owens . Valley in California where crust is under tension . In a normal . the hanging wall slips down relative to the footwall .

Reverse Faults in places where the rock of the crust is pushed together , compression causes reverse faults to . A reverse fault has the same structure as a normal fault . but the blocks move in the opposite direction . Look at Figure to see how the rocks along a reverse fault move . As in a normal fault , one side of a reverse fault lies at an angle above the other side . However . in a reverse fault , the rock forming the hanging wall slides up and over the footwall . Movement along reverse faults produced part of the northern Rocky Mountains in the western United States and Canada . Reverse faults also helped produce the Mountains in northern California . Faults in places where plates move past each other , shearing creates faults . In a full , the rocks on either side of the fault slip past each other side ways . with little up or down motion , A fault that forms the boundary between two plates is called a sliding boundary . The San Andreas fault in ( is an example of a fault that is a sliding boundary . had ! What Is the different between a hanging wall and a ?

iv Online ' EE For Links on faults Web Code ( ii ?

fault In a reverse fault . the hanging wall moves up relative to the footwall . Rocks on either side of a fault . such as the San Andreas fault ( above ) past each other . 117 More Effects of Compression and folding of the crust produce . which arch upward . and , which dip downward . Over millions of years , folding can push up high mountain ranges . Predicting If the In the diagram continued , what kind of fault might form ?

I Activity Modeling stress You can model the stresses that create faults . Knead I piece of plastic putty until it is soft . Push the ends of the putty toward the middle . Pull the ends apart . Push putty one way and the other hall in the opposite direction . Classifying which step in this activity models the type of stress that would produce and ?

ine Changing Earth Surface The forces produced by the movement of Earth plates can fold . stretch , and uplift the crust . Over millions of years . the forces of plate movement can change a llet plain into produced by folding . stretching . and uplifting Earth crust . These landforms include and , folded mountains , mountains . and plateaus . Folding Earth crust Sometimes plate movement causes the crust to fold . Have you ever skidded on at rug that wrinkled up as your feet pushed it across the floor ?

Much as the rug wrinkles . rock stressed by compression may bend without breaking . Folds are bends in rock that form when compression shortens and thickens part of Earth crust . A fold can be only a few centimeters across or hundreds of kilometers wide . You can often see small folds in the rock exposed where a highway has been cut through a hillside . Geologists use the terms anticline and syncline to describe upward and downward folds in rock . A fold in rock that bends upward into an arch is an anticline . shown in Figure . A fold in rock that bends downward to form a valley is a syncline . and are found in many places where compression forces have folded the crust . The collision of two plates can cause compression and folding of the crust over a wide area . Folding produced some of the world largest mountain ranges , such as the Himalayas in Asia and the Alps in Europe . The mountains in northern Coast Range are partly the result of folding . on

Stretching Earth crust When two normal faults cut through a block of rock . a mountain forms . You can see a diagram of this process in Figure . How does this process begin ?

Where two plates move away from each other . tension forces create many normal Faults . When two of these normal faults form parallel to each other . a block of rock is left lying between them . As the hanging wall of each normal fault slips downward , the block in between moves upward . forming a mountain . The Range , which forms the western side of Death Valley . is an example block mountain range in ( If you traveled by car from Salt Lake ( lily to los . you would cross the Great Basin . This region contains many ranges of mountains separated by broad valleys . or basins . This basin and range region Coven much of Nevada and western Utah . The region extends into California Mojave Desert and the area cast of the Siena Nevada . forces in the crust along normal Mountains As tension forces pull the ( rust apart . two parallel normal faults can form a range ot mountains .

noun The Plateau The flat land on the horizon is the Plateau . which forms the North Rim of the Grand Canyon in Arizona The Plateau is part of the Colorado Plateau . Uplifting Earth Crust The that raise can also uplift . or raise , plateaus . A is it large area of flat land elevated high above sea level . Some plateaus form when forces in Earth crust push up a large . flat block of rock . Like a fancy sandwich . a plateau of many different layers , and is wider than it is tall . Forces tho crust Colorado Plateau in the Four Corners region of Arizona . Utah . Colorado . and New Mexico . Much of the Colorado Plateau more than meters iL . Figure shows one part of that plateau in northern . Assessment Target Reading Skill Identify Main Ideas Review the text under Types of Stress . three details that support the main idea that types stress can occur in crust . Reviewing Key Concepts a . Reviewing What are the three main types of stress in rock ?

Relating Cause and Effect How ( hang the shape of crust ?

Comparing and Contrasting Compare the way that compression affects the crust to the way that the crust . I a . Describing What is ?

Explaining hy do faults often occur along plate boundaries ?

Relating Cause and Effect What type oi fault is formed when plates diverge . or pull ?

of Fault is when plates are pushed together ?

a . Listing Name kinds of landforms Eli caused by plate . ta . Relating and Effect What are three ' produced by compression in the crust ?

What is produced by tension ?

Modeling Faults To model Earth crust . roll modeling clay into layers and then press the layers together to form a rectangular black . Use a plastic knife to slice through the block at an angle , forming a fault . Explain which parts of your model represent the land surface . the hanging wall , and the footwall . Then show the three ways in which the sides of the fault can move .

Section Earthquakes and Seismic Waves i Sta Focus Students know that How Do waves quakes are sudden motions along ave breaks in the crust called faults stretch a spring my and that volcanoes and fissures are locations where magma the 00 , reaches the surface . a Students know that the old he other end . an earthquake on any match the region vary . depending on the size my much at the earthquake . the distance of . Have a third classmate 19 region the . the measure and record the distance along the stretched out toy . local geology . and the type of construction in the region . Gather together about four coils of the spring toy and release them . Observe the calls motion . Repeat this step , having a classmate use a stopwatch to time one wave movement How does the energy of an earthquake , Wong , along the spring toy , and then time . ma med Jerk one end of the toy from side to side once . Observe the ma ! he , an coils motion . Repeat this step , again having a classmate time earthquake ?

and record one wave movement . Keep the distance along do the the spring toy the same as in Step ) epicenter of an earthquake ?

mink on , Calculating Calculate the speed of the waves in Steps and . Key Terms ( Hint Divide the distance along the spring toy by the time the wave tool to travel that distance . Which type of wave traveled locus faster ?

How can you explain this difference ?

I epicenter I wave ' Earth is never still . Every day , worldwide . there are several thousand earthquakes . An is the shaking that from the sudden of ruck along at fault . Must . Mme , earthquakes are too small to notice . But a large earthquake can seismograph change Earth and cause great . moment scale The forces of plate cause earthquakes . movements produce stress in crust . adding energy to rock and forming faults . increases along a fault until the rock breaks . An earthquake begins . In seconds . the earthquake releases a large amount of stored energy . Most earthquakes begin in the lithosphere within about kilometers of Earth surI focus ( is the area Earth surface where rock that is under stress . triggering an earthquake . The paint on the surface directly above the focus is called the epicenter ( EP uh sen tur )

Seismic Waves This diagram shows an quake along the Denali fault . An earthquake occurs when rocks fracture deep in the crust . The seismic waves move out in all directions from the focus . Interpreting At what point do seismic waves first reach the surface ?

The Denali lies about south of Fairbanks . Alaska . Types of Seismic Waves like pebble thrown into a pond . an earthquake produces vibrations . waves carry energy as they travel outward . During an earthquake . seismic waves race out from the focus in all directions . Seismic waves are vibrations that travel through Earth carrying the energy during an earthquake . Seismic waves carry energy from an earthquake away from the focus , through Earth interior . and the surface . That what happened in when a powerful earthquake Denali fault in Alaska . shown in Figure , are main categories of seismic waves waves . waves . and surface waves . An earthquake sends out two types of waves from its focus I and waves . When these reach surface at the epicenter . surface waves develop . Seismic waves

Waves The waves to arrive are primary waves . or . shown in Figure . waves are seismic waves that compress and expand the ground like an accordion . Like the other types of seismic waves . waves can damage buildings . waves can move through solids and liquids . Waves After waves come secondary waves . or waves . waves are seismic waves that vibrate from side to side as well as up and down . They shake the ground back and forth . When waves reach the surface , they shake structures violently . Unlike waves . waves can not move through liquids . Surface Waves When waves and waves reach the face . sonic of them become surface waves . waves move more slowly than waves and waves , but they can produce severe ground movements . Some surface waves make the ground roll like ocean waves . Other surface waves shake buildings from side to side . looting which typo of seismic wave causes the ground to ) roll lie ocean waves ! dim 021 The trust vibrates forward and bad along the path of the wave . waves mom , The crust vibrates side to ride and up and down . Direction oi waves Surface waves The ground surface rolls with a wavelike motion . Go For Waves Visit Direction of waves 0133

Video Held Trip ) I Earthquakes Flaunt levels of Earthquake Damage The level of damage caused by an earthquake varies depending on the magnitude of the earthquake and the distance from the epicenter . 1840 Measuring Earthquakes When an earthquake occurs , people want to know How big was the quake ?

There are three commonly used methods of measuring earthquakes the scale , the Richter scale . and the moment magnitude scale . Scale The scale was to rate earthquakes according to their intensity . at strength at given place . The 11 steps of the scale , shown in Figure ) describe the levels ol damage an earthquake can . The earthquake can hav ratings because its intensity varies at locations . For example , an ' intensity generally decreases with distance from the epicenter . This happens because Earth materials absorb some of the waves energy . Also . the quake energy over it wider area as the waves move out the epicenter . The Richter Scale An magnitude is at number that geologists assign to an earthquake based on the size . Geologists determine magnitude by measuring the seismic waves and fault movement that occur during an earthquake . The Richter scale assigns at magnitude number to an based on the of waves . The seismic waves are by a . an instrument that records and measures seismic waves . The Richter scale provides accurate measurements for small . nearby earthquakes . But it does not work well for large or earthquakes .

FIGURE 1110 Scale The scale was Roman numerals to rank earthquakes by how much damage they cause . Applying Concepts How would you rate the three examples of earthquake damage in figure 07 People notice vibrations like those from a passing . Unstable objects disturbed . slight damage . People run outdoors . Moderate to heavy damage . jolted ofl foundation or destroyed . Great destruction . Cracks appear in ground Waves seen on . The Moment Magnitude Scale today often use the moment magnitude scale , a rating system that mates the total energy by an earthquake . The moment magnitude scale can used to rate earthquakes of all sizes , near or far . You may hear news reports that mention 55 ?

the Richter . But the number they quote is always a the moment magnitude for that earthquake . using ca I To rate an earthquake on the moment magnitude scale . 95 geologists first study data from . also usc data on how much movement occurred along the fault and the destroyed cracks form in the ground . Several old brick buildings strength rocks that broke when slipped . and a wage Reading What evidence do geologists use to rate an ( earthquake on the moment magnitude scale ! shelves walls crack people go outside to see happening .

Freon to Data This geologist is ( data collected after an earthquake . These data ( an be used to pinpoint the of an earthquake . Seismic Wave Speeds at five observation stations recorded the arrival times oi the and waves produced by an earthquake . These data are shown in the graph . I . Reading Graphs What variable is shown on the of the graph ?

The ?

Reading Graphs How long did it take the waves to travel ?

Estimating How long did it take the waves to travel ?

Calculating What is the difference in the arrival times of the waves and the waves at ?

At ?

Comparing Earthquakes Ari ' geologists him much stored energy was released by the quake . can range from um to between and . For each mic iii , ground shaking by of 10 . But for catch one number ' in magnitude . amount by factor of about 30 ! A quake releases 50 times is much energy as , and ahout ( times as much as a quake . Thu of an il si ' with . People scarcely notice earthquakes with magnitudes below . Earthquakes with it below are small and cause . with a and ( art cause atc . with a magnitude above can ( Just great . the most putt a magnitude of or above . are rare . Locating the Epicenter Geologists use seismic waves to locate Ill epicenter . Wil ' waves arrive at first . with waves close behind . tell how far the epicenter is from the , the . of the waves and . The farther away an quake is . the greater the time between the arrival the and the waves . Math Mathematical Reasoning , A Pand moo Distance From ( 185

513111 109 ' The map shows how to find the epicenter of an earthquake using data from three stations . Measuring Use the map male to determine the distances from Savannah and Houston to the epicenter Which is closer ?

A then draw at least three circles using data from different set up at stations all over the world . The of each is a particular location . The radius of each circle is the distance from that seismograph to . As you can sec in I the point where the three circles intersect is the location of the epicenter . Huang What do geologists measure to the ' from a to an . Reading section Assessment , Vocabulary Skill Academic Words a . Explaining What type do geologists Explain the and use Iu locate an epicenter ?

in the following sentence waves are In . Interpreting Maps Study the map in seismic that ' and ground . Figure I above , Then the method that scientists to the Renewing Key concepts epicenter of an earthquake . I a . Reviewing How does energy from an earthquake reach Earth surface ?

I . Describing What kind is , each in ( waves ?

Sequencing When do waves arrive at the A puppy , in to and . mug between Wand on the rule . What in magnitude ?

write a short news story describing till . Describing How is magnitude ! Your lead paragraph using the Richter scale ?

should tell , what where , when , and . Applying Concepts What are the advantages hull . Hint ! to of using the moment scale to . an ?

Directed Inquiry Finding the Epicenter ' How can you locate an earthquake epicenter ?

Data Table Difference in Distance to Skills Focus interpreting data . drawing conclusions drawing compass per Denver . Colorado min 40 ( Houston , Tans I min 50 data able showing China Illinois I min differences in ' earthquake arrival times . The graph shows how the difference in arrival time between ' waves and waves depends on the distance lrom the epicenter ' 95 ol the earthquake . Find the in arrival time lor Denver on the of the graph . Follow this line across to the point at which it crosses the curve . To the distance to the epicenter , read down from this point to the of the graph , Enter this distance in the data table . Repeat Step lor Houston and Chicago . Set your compass at a radius equal to the distance from Denver to the earthquake epicenter that you previously recorded in your data table . Draw a circle with the radius determined in Step , using Denver as the center Draw the circle on your copy of the map . Hint Draw your circles carefully . You may ?

need to draw some parts of the circles off the map . Repeat Steps It and for Houston and Chicago . la . is 54000 ) Analyze and conclude conclusions Observe the three circles you have drawn . Where is the earthquake epicenter ?

Measuring which on the map is closest to the earthquake epicenter ?

far . in kilometers . is this city from the epicenter ?

Inferring In which of the three cities listed in the data table would detect the earthquake ?

Last ?

About how far from San Francisco is the epicenter that you found ?

What would be the difference in arrival times of the waves and waves for a recording station in San Francisco ?

Interpreting Data What happens to the difference in arrival times between waves and waves as the distance from the earthquake increases ?

Review the procedure you followed in this lab and then answer the following question . when you are trying to locate an epicenter . why is it necessary to know the distance recording stations ! More to Explore You have just located an earthquake epicenter . Find this earthquake location on the Earthquake Risk in the United States ( Figure 18 ) What is the risk of earthquakes in the area of this quake ! New look It the map of Earth Plates ( Figure 22 in the chapter Plate Tectonic ) What conclusions can you draw from this map about the cause of earthquakes in this area ) Oil !

900 Section Monitoring Earthquakes Standards Students know thatthe ol an earthquake on any region vary . depending on the size at the earthquake . the distance of the region the epicenter , the geology , and the type of in the region . How da work ?

How do geologists ?

How are data used ?

Key Terms How can Seismic Waves Be Detected ?

Using scissors , cut plastic stirrers in half . Each piece should be about long . Your teacher will give you a pan containing gelatin . insert the stirrer pieces into the gelatin , spacing them about ( apart in a row . The pieces should stand upright . but not touch the bottom of the pan . At the opposite end of the pan from the stirrers . gently tap the surface of the gelatin once with the eraser end of a pencil . Observe the results . Think It Over Inferring What happened to the stirrer pieces when you tapped the gelatin ?

What was responsible for this effect ?

Look at the beautiful in the photo . You might be surprised to learn that the vase is actually a instrument . Can you guess what it was designed to do ?

an , designed and built this earthquake detection device in China nearly years ago . It is said to have detected an earthquake centered several hundred away . are dangerous , so people want to monitor them . Tu monitor meme to watch closely . Like the ancient Chinese . many societies have used technology to mine when and where earthquakes have occurred . During the late . scientists developed that were much more sensitive and than any earlier devices . mun 11 Earthquake Detector years ago . a Chinese scientist invented this instrument to detect earthquakes .

The Seismograph A simple seismograph can consist of a heavy weight attached to a frame by a spring or A pen connected to the weight rests its point on a drum that can rotate . As the drum rotates slowly , the pen draws a straight line on paper wrapped tightly around the drum . Seismic waves cause the drum to vibrate . But the suspended weight with the per attached move very little . Therefore , the pen stays in place and records the drum vibrations . Measuring Seismic Waves When you write a sentence . the paper stays in one place while your hand moves the pen . But in a seismograph . it the pen that remains still while the paper moves . Why is this ?

All seismographs make use of a basic principle of physics Whether it is moving or at rest , every object resists any change to its motion . A heavy weight resists motion during a quake . But the rest of the seismograph is anchored to the ground and vibrates when seismic waves arrive . Reading I You have probably seen a pattern of lines used to represent an earthquake . The of lines , called a . is the record of an seismic waves produced by a seismograph . Study the gram in Figure and notice when the waves , waves , and surface waves arrive . The height of the jagged lines drawn on the seismographs drum is greater for a more severe earthquake or for an earthquake ( lose to the ' What A . fastest and arrive . shortly after waves . on the . Flaunt Recording Seismic Waves A seismograph records seismic waves . producing a . Today . electronic contain sensors instead of pens . Diagrams What is the function of the weight in the travel swans arrive waves the largest disturbance .

! INKS , Links on measurement Visit Web Cede Instruments That Monitor Faults Along It fault , scientists may detect a slight rise or fall in the elevation and tilt of the land . Geologists think that such changes signal a buildup of stress in rock . Increasing stress could eventually lead to an earthquake . To monitor faults , geologists have developed to measure changes in elevation , tilting of the land surface , and ground movements along faults . Some of the instruments that use to monitor these movements include . creep meters , and satellites . meters A measures tilting or raising of the ground . lfyou have ever used a carpenter level , you have used a type of . The used by geologists consist of two bulbs that are with a liquid and connected by a hollow stem . Notice that if the land rises or falls slightly . the liquid will flow from one bulb to the other . Each bulb contains a measuring scale to measure the depth of the liquid in that bulb . Geologists read the scales to measure the amount of tilt occurring along the fault . Creep Meters A creep meter uses at wire stretched across it fault to measure horizontal movement of the ground . On one of the fault . the wire is anchored to a post . On the other side , the wire is attached to a weight that can slide if the fault moves . Geologists determine how much the fault has moved by measuring how much the weight has moved against a scale . Devices A device uses a laser beam to detect movements The device times a laser beam as it travels to at and back . Thus . the device can detect any change in distance to the reflector . Scientists can monitor changes in elevation as well as horizontal movement along faults using a network of satellites called . the Global System . was developed to help ships and planes their routes . As shown in Figure 14 . can also be used to locate points on Earth surface with great precision . Using . scientists measure tiny movements of markers set up on the opposite sides of a fault . How door I met rum work ?

14 Monitoring Faults To detect slight motions along faults in California use several types of devices . Comparing and Contrasting Which of these devices measure horizontal movement ?

Which one measure vertical movement ?

Wire Creep Meter A ?

horizontal movement . satellite San Andreas fault Satellites receivers use the satellite system to measure changes in elevation and tilt of the land as well as horizontal movement along a . scale A measures vertical movement . Observatory housing a laser A device measures horizontal movement .

. Activity Measuring Friction You can measure the force of friction . Place a small weight on a smooth , flat tabletop . Use a spring scale to pull the weight across the surface . How much force is shown on the spring scale ?

Hint The unit of force is newtons . Tape a piece of sandpaper to the tabletop . Repeat Step , pulling the weight across the sandpaper . Is the force of friction greater for a smooth surface or for a rough surface ?

San Francisco Using Seismographic Data Scientists collect and use seismographic data in a variety of ways . Seismographs and devices provide data used to map faults and detect changes along faults . Geologist are also trying to use these data to develop I method of predicting earthquakes . Mapping Faults Faults are often hidden by a thick layer of rock or soil . How can geologists map a hidden fault ?

When seismic waves hit a fault . the waves are reflected off the can detect these reflected seismic waves . Geologists then use these data to map the fault length and depth . Knowing the location of hidden faults helps determine the earthquake risk for the area Monitoring Changes Along Faults Geologists study the types of movement that occur along faults . How move along a fault depends on how much friction there is between the sides of the fault . Friction is the force that opposes the motion of one surface as it moves across another surface . Friction exists because surfaces are not perfectly smooth . Where friction along a fault is low . the rocks on both sides of the fault slide by each other without much sticking . fore stress does not build up . and big earthquakes are unlikely . Where friction is moderate , the sides of the fault jam together . Then from time to time they jerk free , producing small quakes . Where friction is high . the rocks together and do not move . in this case , stress increases until it is strong enough to overcome the friction force . For example . in most places along the San Andreas fault in California , friction is high and the plates lock . Stress up until an occurs . Hours 15 Earthquake list in The map shows one attempt to rate the probability of a strong earthquake along the San Andreas fault . it high percent probability means that a quake might be more likely to occur . Inferring What do scientists think is the risk on strong earthquake near San Francisco ?

Target Reading Skill Identify Main ideas Figure shows how geologists in California have used data about how the San Andreas fault moves . They have tried to estimate the earthquake risk along the fault . Unfortunately , this attempt at earthquakes has not worked yet . trying to Predict Earthquakes Even with data from many sources . geologists ca predict when and where a quake will strike . Usually , stress along a fault increases until an earthquake occurs . Yet times stored energy builds up along a . but an earthquake fails to occur . Or , one or more small would relieve only some of the stored energy along the fault . There is always the chance that at large . destructive earthquake will release most of the stored energy . So exactly what will happen remains uncertain . The problem of predicting earthquakes is one of many questions that remain unsolved . If you become a scientist . you can to find answers in these questions . Much to be discovered ! a ' EMm Why is it difficult to predict earthquakes ?

Section Review text under Monitoring Along Faults . identify two or three details that support the main idea that friction along helps to determine the risk of earthquakes . Reviewing Key Concepts What is a seismograph ?

Explaining How docs a record seismic waves ?

A records a strong earthquake and at weal earthquake , How would the lot lhe two ?

Reviewing What four instruments are to monitor ?

Describing What anget does each instrument Inferring A satellite that monitors a fault detect an increasing tilt in the land . What could this change in the land surface indicate ?

500 16 Saint Data A geologist interprets a seismogram . Understanding changes that precede earthquakes may help in efforts to predict them . Writing an . Listing What are three ways in which geologist use data ?

graphic data to maps of faults ?

collect faults ?

data on along the sides of Writing in Science ! You an an Inventor who has created a simple device that can detect an earthquake . To protect your rights to the invention . you apply tor a patent . in your patent application . describe your device and how it will indicate the direction and strength at an earthquake . You may include a sketch . 195 ii . Explaining Hair do ( A . Making Generalizations Why do geologists

Section Earthquake Safety FINN Standards Focus Students know that the effects of an earthquake on any region vary . depending on the size of the . the distance of the region from the epicenter , the local geology . and the type of in the regions Students know quakes . volcanic eruptions , slides . and change human and wildlife habitats . How do geologists determine earthquake risk ?

What kinds of damage does an earthquake cause ?

What can be done to increase earthquake safety and reduce earthquake damage ?

Key Terms I liquefaction I aftershock ' tsunami I building , Standards Can Bracing Prevent Building Collapse ?

Tape four straws together to make a square frame . Hold the frame upright on a flat surface . Hold the bottom straw down with one hand while you push the top straw to the left with the other . Push it as far as it will go without breaking the frame . Tape a fifth straw horizontally across the middle of the frame . Repeat Step . Think It Over Predicting What effect did the fifth straw have ?

What effect would a piece of cardboard taped to the frame have ?

Based on your observations , how would an earthquake affect the frame of a house ?

Imagine being sound asleep in your bed in the of the . you an as your begins to rattle and shake . As objects fall off shelves and walls track , you ii dusk for . Around the city . collapse and fires out . The quake than it minute . but leaves behind great . That what in zi quake hit Taipei , Taiwan . The effects an earthquake on any itl ) depending on the sim of . from the . local geology . and the type in the . 17 Earthquake Rescue After an earthquake in Taipei , crews rescued victims in collapsed buildings .

Earth Risk in the United States Earthquake Risk Geologists know that earthquakes are likely wherever plate movement stores energy in the rock along faults . determine earthquake risk by locating where faults are active , when put earthquakes have occurred . and wherethe most . Plate Boundaries and Faults Look at Figure 18 . In the United States . the risk is highest along the coast in . Washington . and Alaska . Plates meet along the coast . causing many active faults . In California , the plate and North American plate meet along the San Andreas fault . In Washington . earthquakes result from the subduction of the luan de plate . In Alaska , subduction of the plate causes many earthquakes . The eastern United States mostly has a low risk of quakes because this region lies far from plate boundaries But the East has had some of the most powerful quakes in the nation history . Scientists think that the continental plate forming most of North America is under stress . This stress could disturb faults hidden beneath soil and rock . half ! What anus ol the United States have the highest ' earthquake risk ?

II The map shows areas where serious earthquakes are likely to occur . based on the locations of previous earthquakes . Interpreting Maps Where are damaging earthquakes least likely to occur ?

Most likely to occur ?

Go For More an earthquake Welt ( ode Chapters ! From 19 Lorna The 1989 Lorna earthquake along the San Andreas fault . The map shows the intensity ol shaking felt in areas by the earthquake . Mayor Earthquake ' tan . 1908 i Tokyo , Japan , Southern Chile . Alaska , Lorna , California . 1939 Northridge . California . 1994 lndian Ocean . near Sumatra . Indonesia , 2004 hour 10 Major The table shows strong earthquakes of the past years and their magnitudes Calculating About how much more powerful is a magnitude earthquake than a magnitude earthquake ?

None . Very light ( some windows break ) Light ( some plaster falls ) Moderate to heavy ( chimneys and walls fall ) Heavy ( building foundations ground cracks ) Very heavy most structures destroyed rails bend ) Mapping Earthquake Intensity Geologist can use scale data to map the intensity of an earthquake . Intensity maps show how the ground shaking and damage from an earthquake vary from place to place . You can see an example of this type of map in Figure 19 . Why are intensity maps important ?

These maps show that arms near faults generally suffer the most serious damage . And the same areas might suffer damage again if struck by another strong quake . Historic Earthquakes Why do geologists study earthquakes that happened many years ago ?

Past earthquakes can help geologists estimate the risk of future earthquakes . One way that geologists learn about past earthquakes is from historic reports These reports may describe where the quake was strongest and what damage it caused . Geologists also study the rock and soil along Faults for of past earthquakes . Geologists cart use these data to estimate the magnitudes of earthquakes that occurred before the seismograph was invented '

How Earthquakes Cause Damage When a major earthquake strikes , it can cause great damage . But distance from an epicenter is not the only factor involved . of earthquake damage include shaking , liquefaction , and . Shaking The shaking produced by seismic waves can trigger landslides or avalanches . These disasters can bury and destroy both buildings and the natural areas wildlife need in order to live . Shaking itself can also damage or destroy buildings and bridges . topple utility poles . and fracture gas and water mains . waves and surface waves . with their and movement . can cause severe damage to buildings near the epicenter . The types of rock and soil where and how much the ground shakes . The most violent shaking may occur kilometers away from the epicenter . Loose soil shakes more violently than solid rock . This means a house built on sandy soil will shake more than a house built on solid rock . Liquefaction In . when it powerful earthquake roared through Anchorage , Alaska , wide cracks opened in the ground . The cracks were created by liquefaction . liquefaction ( lik wih FAX shun ) occurs when an earthquakes violent shaking suddenly turns loose , soft soil into liquid mud . Liquefaction is likely where the soil is full of moisture . As the ground gives way , buildings sink and pull apart . Aftershock Sometimes . buildings weakened by an quake collapse during an aftershock . An is an quake that occurs after a larger earthquake in the same arm . may strike hours . days . or even months later . Mapping Magnitude . Obtain an outline map of the world with latitude and longitude . Use reference sources to find out the locations of the earthquakes in Figure 20 and plot them on the map . Use a different symbol to mark quakes with a magnitude of or more . Compare your map with the map of plate boundaries in Figure 22 on . Notice what type of plate boundary lies near the magnitude earthquakes . What process takes place at the plate boundaries near the magnitude earthquakes ?

How does this help to explain why these quakes are so powerful ?

Mint 21 Liquefaction Damage An earthquake caused the soil beneath this building to . Liquefaction can change soil to liquid mud . Posing Questions Whatare some questions people might ask before building in a area ?

tumors 01 ! Wave height is low over open ocean . Flam 12 How I Form A tsunami begins as a low wave . but turns into a huge wave as it nears the shore . In a powerful earthquake In the Indian Ocean triggered several tsunamis . The caused great loss of life and destruction to coastal areas around the lndian Ocean . 2000 Wave height Increases greatly near shore . When an earthquake jolts the ocean floor . plate causes the ocean to rise slightly and push water out of its way . The water displaced by the earthquake may form a large wave called a tsunami ( NAH mee ) shown Figure 22 . A tsunami spreads out from an ( center and speeds across the ocean . In the open ocean . the height of the wave is low . As a tsunami approaches shallow water , the wave grows into a mountain of water . Steps to Earthquake Safety What should you do earthquake strikes ?

The main danger is from falling objects and glass . OThe best way to protect yourself is to , and hold . If you are indoors when A quake strikes . drop down and crouch beneath a sturdy table or desk and hold on to it . if no desk or table is available . crouch against an inner wall . away from the outside of a building . and cover your head and neck with your arms . Avoid windows . mirrors . wall hangings . and furniture that might topple . If you are outdoors . move to an open area such as a ground . Avoid vehicles , power lines . trees . and buildings . Sit down to avoid being thrown down . After a quake . water and power supplies may fail , food stores may be closed . and travel may be difficult . People may have to wait days for these services to be restored To prepare . store an earthquake kit containing canned food . water , and first aid supplies where it is easy to reach . 15 ) How can be dangerous during a quite ! How can It protect you ?

Designing Safer Buildings Most deaths and injuries result from age to buildings or other structures . To reduce earthquake damage , new buildings must be made stronger and more . Older building may he so as to withstand stronger quakes . Figure 23 shows some of the steps that can make houses . Generally . the effects of an earthquake of the type of construction . Buildings made of brittle materials such as concrete or brick suffer the most damage in an earthquake . Buildings made of more materials , such as wood , tend to suffer less damage . Tall buildings an more subject to age than buildings , Secure brid with metal brackets and . fasten bookshelves , and tail dressers to wall studs . Bolt the house to its concrete foundation . Strap the water heater to the wall . 23 An House People can take a variety of steps to make their hornet safer in an earthquake . Predicting During a quake . what might happen to house that was not to its foundation ?

Remove heavy items from the walls above beds . Position beds from windows . TI ! panels to strengthen the walls Use metal to strengthen the houses frame . chapters on ! Reviewing Key Concepts . What factors help geologists determine earthquake risk for a region ?

Comparing and contrasting Why does the I risk of quakes vary across the United States ?

a . Listing What are four ways that earthquakes , Stable or Unstable ?

Make a model of a fault by placing two small . folded towels side by side on a flat surface . File a stack of books on the fault by placing light books on the bottom and heavy ones on top . Gently pull the towels in opposite directions until the pile topples . Repeat the process . but this time with the heavier books on the bottom . Relating and which one of your structures was more stable ?

why ?

Section Vocabulary Academic Words What are two things you would do to construct a building so that it could withstand an ?

Lise the word in your answer . cause damage ?

It . Relating Cause and Effect How does cause damage during an earthquake ?

Developing Hypotheses How might heavy rain before an earthquake affect the danger of liquefaction ?

Assessment Protecting Structures way in which a building is determines whether it can an earthquake . During an earthquake , brick buildings and some buildings may collapse walls have not been reinforced , or . To combat damage caused by liquefaction , new homes built on soft ground should be anchored to solid rock below the soil . Bridges and highway overpass can be built on supports that go through soft soil to ground . To out more about how buildings can withstand earthquakes , look at ' Buildings on the following pages . A building is designed to reduce the amount of energy that reaches the building during an earthquake . A building rests on rubber pads or springs . Like the suspension of at car . the pads and springs smooth out a bumpy ride . During a quake . the building moves gently back and forth without any violent shaking . Making Utilities Safer Earthquakes cam cause tire and when gas pipes and water mains break . Flexible joints can be installed in gas and water lines to keep them from breaking . Automatic valves also can be installed on these lines to cut gas and water . How an be protected front earthquake leading , damage ?

Eu . I . Reviewing How can you protect yourself during an earthquake ?

What will happen to a building when seismic waves strike the building during an earthquake ?

Quake Plan Work with an adult family member to develop an earthquake safety plan . The plan should tell family members what to do during an earthquake . it should list items your family would need if a quake cut power and water lines it should also explain where to shut off the gas if your home has a natural gas line . Share your earthquake safety plan with the rest of your family .

Guided inquiry Earthshaking Events . Problem How can you use I map of bolts and historic earthquakes to analyze earthquake risk In California ?

Skills FOCUS interpreting maps , inferring Procedure . Using a piece oi tracing paper and a pencil . trace the outline of California in Figure is on page 237 . Trace and label the latitude and longitude lines and the map scale . Mark the location of your community on your map . In a second color , trace the state active Label the faults . Use the map scale to measure the distance from your community to the nearest fault . Record the distance . In a third color . plot the epicenters of the earthquakes in the table . Also draw lines to shade approximately the parts of the San Andreas fault that moved during the Fort Tejon and San Francisco earthquakes . Measure the distance from your community to the nearest epicenter of a historic earthquake . Record the distance . Analyze and conclude Interpreting Maps What major fault is closest to your community ?

Interpreting Maps What historic was closest to your community ?

What was the earthquakes magnitude ?

inferring Based on your distance from an active fault and historic earthquake , how would you rate the earthquake risk in your area ?

Communicating Write a paragraph explaining the earthquake risk in your community . in your answer , include factors such as the role of plate tectonics , active faults . and historic earthquakes . More to Explore Vou can further analyze earthquake risk in your community . Conduct research on nearby active faults and past earthquake activity , ground motion , and faulting , Write a report based on your research southern San Andreas . 37 ' northern San Andreas 37 ' Fort , 1357 Owens Valley , 1872 San Francisco . 1906 Calaveras 1911 Long Beach , 193 ! imperial Valley . 1940 Concord . 1954 San Fernando . 1971 Gerda Plate , Lorna . 1989 , 1994 , 200 ! na ' I ' na ' chapters 9203

Technology and in melting one thin twig does much force . Breaking a bundle of twigs does . like one thin twig , the walls . beams . sun . wan A shear and other supporting pen of I building ' can map as seismic energy travels through the structure . Reinforcing i , parts makes them more llke the bundle of and less likely to snap when a quite . Tension Ties These tie Ihe floors and A i di ceiling or a building to the buildings have types of construction 790550 5150 that reduce earthquake damage . Some oi these features strengthen a building . Others allow the mag building 10 move or shield the building from the energy of seismic waves . in areas , most tall buildings may have one or more of the features shown here , Base These pads separate , or , a building from its foundation and prevent some of an earthquake energy from entering the building .

. But at What Cost ! save lives and reduce damage . Despite these , the technologies ! mu have drawbacks . as ( hum cross braces , may reduce the amount of usable placed space in a building . It is also expensive to add seismic features to an existing building Communities must make between the absorb dur . an ' benefits and the costs of buildings . Dampers Dampers work like the shock absorbers in a ( to absorb some oi the energy of . Even buildings need design features . Flexible Pipes Water and gas pipes have flexible . Flexible pipes bend as energy passes through them . greatly damage . Weigh the Impact Identify the Need Your ( ity has hired you to deride which buildings or other structures most need to be able to withstand an earthquake . List three types of structures that you think need to be . Research how the structures on your be made safe . house one structure from your list and make notes on how it can be made sale Write Using your notes , write a report that explains how your structure an be designed or modified ti withstand earthquakes . For More on buildings ' Visit Web Code (

Chapter ' Forces in Earth Key , it I Tension , and shearing nver of ) lI ' A to the and volume of rock . Faults usually occur along plate ( where the of plate motion or pull the crust so much that the ( rust . an titre main types ui faults normal fault . reverse , and ( Over years . the of plate can change a Hat plain into such as and . folded mountains . and . Key Terms stress hanging wall tension reverse fault shearing fault normal fault plateau ' Earthquakes and Waves Key Concepts . Seismic waves catty energy from an unite away lrom the locus . interim . and across the surface . Three used , lit measuring are the scale . the Ri ( hIL ' the moment scale . GE ( use ' locate an epicenter . Key Terms ' scale magnitude epicenter Richter scale I wave wave moment scale surface wave 205 Study Guide Plat motions stress in Earth trust that leads to faults , mountain building . and earthquakes . Monitoring Earthquakes Key Con ( I During an , seismic the drum to vibrate . the suspended weight with the pen attached moves very little . the pen stays in place and records the . To monitor faults . have developed tu in elevation . tilting of the land surface , and ( along , and devices data med In map faults and detect along faults . Key Terms friction Earthquake Safety Key Concepts , arm Geologists can determine risk by locating where faults are past earthquake have , and ' past have the must damage . Cause oi include shaking , and tsunamis . The hut way In protect yourself is to drop . and hold . To reduce ua . new buildings must he made and inure . Older may he to withstand stronger . Key Terms liquefaction tsunami aftershock base isolated building

Review and Assessment Reading Skill ' Main Ideas ' under the uf Faults in Section the Reviewing Key Ter Choose the letter of the best answer . putt ( to become shorter and thicker is . normal . ii wall ofa fault slips ( with respect to the . the mull is reverse fault . it . normal . strike . Whith is of . lor ?

moment magnitude scale it . limits scale ( scale Richter scale . The ' mi are it . I wes . vim . tsunamis . in the atter an earthquake , people nul go inside a , even if it . a . liquefaction . vi . i For Sell Assessment Visit om Web Code ' Kinds of Faults ' in Science Detail Detail Detail mi ?

Normal wall slips down relative Complete the following sentences so that your answers clearly explain the key . Compression is is turn . MINT . in Earth can MINT normal fault , whi ( is . an epicenter lies the a focus . is . Alter an , seismic arrive are waves . which are 10 . An can trigger i tsunami . whith la Paragraph Now that you have teamed about the awesome power of earthquakes , write a paragraph about how earthquakes cause damage . Discuss both the natural and that contribute to an earthquake destructive power . Saul Earthquakes Chapter 207

Review and Assessment Checking Concepts 11 . What causes stress ui Earth crust ?

10 009515005 11 . how ( Arrival times of and waves 13 . What type stress in the crust results in the til ?

Explain . in 14 . Win ! are . Jud how do they form ?

15 . happens along a beneath Earth surface when an earthquake ( Cut ' a . 16 . How the oi by an related to its ' 17 . What docs the height ut the lines on a indicate ?

can and structures is protected from ?

Minutes interpreting Diagrams in what order did the ( ill ' at the ?

19 . unit At the til a limit . tilt how the wall in relation to the . What kind of is rim ?

15 . Data Whatwas the difference in arrival times for the waves and ?

16 . Predicting What would the look like alter ?

would it change it an aftershock occurred ?

Standards investigation 20 . Analyzing Data A has data ) in Performance Assessment Before testing how 24 . Interpreting which ut seismic wave the largest ground ?

from two stations . your an earthquake , to is this information the your how and why yuu your of the ?

ur why not ?

model . your model is tested . how it withstands the . wuuld a real with the method used to test your ?

it it were at real building , cuuld re withstand an How could you your modal ?

21 . ri ) fault that has frequent earthquakes . How will the fault alike ! the street ?

22 . Matting Generalizations ' Lind and lame . soil tit caused by an earthquake ?

Explain . 20 ! ' Choose the letter oi the best answer . I . The diagram below shows how stress affects a mass of rock in a process called A I tension . squeezing . shearing . The diagram below shows fault like the San Andreas fault in California . Movement along the fault occurs because of A tension in the . I uplift of the crust . plate motions . volcanic activity . Stress will until an earthquake if friction along Fault is A decreasing . I high . low . changed to heat . To estimate the total energy released by an earthquake . a geologist should use the A sale . I Richter scale . epicenter scale . moment magnitude scale . Standards Practice ?

at Use the information below and your knowledge of science to answer Questions and . Seismic waves . In the diagram . the epicenter is located at point A I . When an earthquake occurs , seismic waves travel A from in all directions . I from In from in all directions . Which answer best explains how earthquakes can change an area where wild animals live ?

A A landslide covers a forest . I A tsunami washes away a sand dune . Soil to liquid mud . All of the above . mu Idea . motions can cause tension in crust . Explain haw tension could lead to the of II fault . a type of an . chapters 9309