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Main Menu Table of Contents Print Back Name: ________________________ Class: ___________________ Date: __________ ID: A Chapter 9: Earthquakes -- Multi-format Test Modified True/False Indicate whether the statement is true or false. If false, change the identified word or phrase to make the statement true. ____ 1. Divergent fault boundaries are especially likely to cause earthquakes. _________________________ ____ 2. When the kinetic energy built up in a plate exceeds the strength of the rock an earthquake occurs. _________________________ ____ 3. Secondary, or S-waves are only able to travel through liquids inside Earth. _________________________ ____ 4. Seismic waves are recorded and measured by an instrument called a seismologist. _________________________ ____ 5. The Mercalli scale rates earthquakes according to the size of the seismic waves recorded on a seismograph. _________________________ ____ 6. The San Andreas fault is an active fault that causes many earthquakes to occur in the city of San Francisco, California. _________________________ Completion Complete each statement. Select the correct term to complete each sentence. There are extra terms in the list. transform slickenslides foreshocks focus converging stick-slip body epicenter diverging aftershocks surface fault 7. An earthquake is a form of _________________________ motion. 8. ____________________ plate boundaries are especially likely to cause earthquakes. 9. The ____________________ is the point below the surface where the rock breaks in an earthquake. 10. A ____________________ is a break in the rock of Earth’s surface where movement occurs to cause earthquakes. 11. Seismic waves are also known as ____________________ waves because they travel through the interior of Earth. 12. The seismic waves from an earthquake are usually strongest at the ____________________. 13. ____________________-waves cause the most damage to buildings above ground. Short Answer 14. List the three things that are needed for stick-slip motion. 15. Describe the differences between shallow focus earthquakes and deep focus earthquakes. 16. Describe the movement of P- and S-waves and explain how fast they move in relation to each other. 1 Main Menu Table of Contents Print Back Name: ________________________ ID: A 17. Why has San Francisco experienced several severe earthquakes and many smaller ones? 18. What type of information does a seismograph give about seismic waves? 19. The diagram above shows the focus of an earthquake and how its seismic waves travel through the interior of Earth. Which of the waves is an S-wave and which is a P-wave? Explain how you know. 20. After a minor earthquake, a Los Angeles, California, newspaper’s headline reads: “Blame Plate Tectonics.” What do you think this means? Problem 21. Assume that P-waves travel through Earth at an average speed of 6 km/s. A seismic station is located 72 km from the epicenter of an earthquake. How many seconds did it take for the P-waves to arrive at this seismic station? 22. The distance scale on a map is 1 centimeter = 25 kilometers. The distance from a seismic station to the epicenter of an earthquake is 75 kilometers. To locate the epicenter, what would be the radius of the circle that is drawn around this station on a map? 23. Assume that P-waves travel at an average of 6 km/s and S-waves travel at an average of 4 km/s. The P-waves from an earthquake reach a seismic station in 7 seconds. How long will it take the S-waves to arrive at this same station? 24. Assume that P-waves travel at 6 km/s and S-waves travel through Earth at 4 km/s. It takes 13 seconds for the S-waves to reach the seismic station. How much longer did it take the S-waves to arrive at the station compared to the P-waves? Essay 25. Explain in detail what happens when a large earthquake occurs in a city. In your answer be sure to discuss the different types of seismic waves, foreshocks, and aftershocks. Assume the city receives all types of seismic waves as well as foreshocks and aftershocks. 2 Main Menu Table of Contents Print Back ID: A Chapter 9: Earthquakes -- Multi-format Test Answer Section MODIFIED TRUE/FALSE 1. ANS: F, Transform PTS: 1 2. ANS: F, potential DIF: basic REF: section 9.1 PTS: 1 3. ANS: F, solids DIF: basic REF: section 9.1 PTS: 1 DIF: basic 4. ANS: F, seismograph REF: section 9.2 PTS: 1 5. ANS: F, Richter DIF: basic REF: section 9.2 PTS: 1 6. ANS: T REF: section 9.4 DIF: advanced REF: section 9.3 PTS: 1 COMPLETION 7. ANS: stick-slip PTS: 1 8. ANS: Transform DIF: basic REF: section 9.1 PTS: 1 9. ANS: focus DIF: basic REF: section 9.1 PTS: 1 10. ANS: fault DIF: basic REF: section 9.1 PTS: 1 11. ANS: body DIF: basic REF: section 9.1 PTS: 1 12. ANS: epicenter DIF: basic REF: section 9.2 PTS: 1 13. ANS: Surface DIF: intermediate REF: section 9.1 PTS: 1 DIF: intermediate REF: section 9.2 1 DIF: basic Main Menu Table of Contents Print Back ID: A SHORT ANSWER 14. ANS: 1. Two bodies that are in contact, but are able to move. 2. Forces that will make them move 3. Friction strong enough to stop them from moving at first. PTS: 1 DIF: intermediate REF: section 9.1 15. ANS: Shallow focus earthquakes are when the focus of the earthquake is less than 50 kilometers below the surface. Deep focus earthquakes are when earthquakes occur deeper inside Earth, often at subduction zones. PTS: 1 DIF: advanced REF: section 9.1 16. ANS: P-waves push and pull the rock as it moves through it, in the same direction as the traveling wave. S-waves cause the rock to move in a side-to-side motion, across the direction of the traveling wave. P-waves travel faster than S-waves. PTS: 1 DIF: intermediate REF: section 9.2 17. ANS: The San Andreas Fault runs directly through the city of San Francisco. The city has experienced several earthquakes and will continue to experience earthquakes in the future because this is currently a very active fault. PTS: 1 DIF: basic REF: section 9.4 18. ANS: Seismographs show the kinds of waves that occur, their strength, and the time that they arrive at the instrument. PTS: 1 DIF: basic REF: section 9.2 19. ANS: Wave A is an S-wave. S-waves cannot travel through the liquid outer core, and are deflected back into the mantle. Wave B is a P-wave. P-waves can travel through the liquid outer core. PTS: 1 DIF: intermediate REF: section 9.2 20. ANS: California has had another earthquake. California is close to two convergent plates, the Pacific and the North American. Pressure builds up in Earth’s crust in California, and when the pressure is released, there is an earthquake. There is also a major fault in California, the San Andreas Fault. PTS: 1 DIF: intermediate REF: section 9.3 2 Main Menu Table of Contents Print Back ID: A PROBLEM 21. ANS: Rate of speed = distance time time = distance speed time = 72 km = 12 s 6 km/s PTS: 1 22. ANS: 3 cm DIF: intermediate REF: section 9.2 PTS: 1 DIF: intermediate REF: section 9.2 23. ANS: First find the distance the seismic station is from the epicenter using the following formula: distance Rate of speed = time distance = speed × time = 6 km/s × 7 s = 42 km The station is 42 km from the epicenter. Use this and the speed of the S-waves to figure out the time it takes the S-waves to arrive at the station: distance time = speed time = 42 km = 10.5 s 4 km/s PTS: 1 DIF: advanced REF: section 9.2 24. ANS: First find the distance the station is from the epicenter using the speed and time of the S-waves. distance = speed × time = 4 km/s × 13 s = 52 km Next find out how long it took the P-waves to travel from the epicenter to the station. distance time = speed time = 52 km = 8.7 s 5 km/s Subtract the P-wave time from the S-wave time to find out how much longer it took the S-waves to reach the station. 13 s − 8.7 s = 4.3 s PTS: 1 DIF: advanced REF: section 9.2 3 Main Menu Table of Contents Print Back ID: A ESSAY 25. ANS: During an earthquake, there is a strong burst of shaking that last for a few minutes. Foreshocks are small bursts of shaking or tremors that may precede a large earthquake. Foreshocks can occur days to minutes before the earthquake hits. During an earthquake, the primary waves (P-waves) arrive at the city first because they are the fastest type of seismic waves. P-waves push and pull the rock as it moves through it. The secondary waves (S-waves) are the next type of seismic wave to arrive at the city. These waves move slower than P-waves. S-waves will cause the ground in the city to move in a side-to-side motion across the direction of the traveling wave. The last wave to arrive is the surface wave. These waves occur directly at the surface and are the slowest of the three types of waves. Surface waves can move up and down and also side-to-side, they cause the most damage. After the earthquake aftershocks can occur that can last for hours to days after the earthquake. Aftershocks are small tremors that follow an earthquake. PTS: 1 DIF: advanced REF: section 9.2 4