Earthquakes Packet 5 Your Name Group Members Score Minutes Standard 4 Key Idea 2 Performance Indicator 2.1 Use the concepts of density and heat energy to explain observations of weather patterns, seasonal changes, and the movements of Earth s plates. Major Understanding: 2.1j Properties of Earth s internal structure (crust, mantle, inner core, and outer core) can be inferred from the analysis of the behavior of seismic waves (including velocity and refraction). Analysis of seismic waves allows the determination of the location of earthquake epicenters, and the measurement of earthquake magnitude; this analysis leads to the inference that Earth s interior is composed of layers that differ in composition and states of matter. 2.1l The lithosphere consists of separate plates that ride on the more fluid asthenosphere and move slowly in relationship to one another, creating convergent, divergent, and transform plate boundaries. These motions indicate Earth is a dynamic geologic system. These plate boundaries are the sites of most earthquakes, volcanoes, and young mountain ranges. Compared to continental crust, ocean crust is thinner and denser. New ocean crust continues to form at mid-ocean ridges. Earthquakes and volcanoes present geologic hazards to humans. Loss of property, personal injury, and loss of life can be reduced by effective emergency preparedness.
Mini Lesson 1: Earthquakes An earthquake is the shaking of Earth s crust. The most common cause is the interaction between lithospheric plates (movement of plates). Convection currents cause the plates to move. These plates are very rigid and although they are not attached to each other, it is almost as if they are interlocked. It takes an incredible amount of force to get them to actually move relative to each other. Once enough pressure has built up and the plates move, there is an enormous amount of energy released. This is why most major earthquakes occur at or near plate boundaries. Other causes of an earthquake can be a meteor impact, collapse of large building or even a major landslide. Damage from earthquakes can range from buildings and bridges collapsing to fires and even water shortages. Earthquakes that occur in or near oceans may cause tsunamis. These giant waves can be devastating and cause extensive damage to coastal areas. It is important to understand what causes earthquakes and where they are most common so that people can prepare to react when they occur. Need to know: 1. What is an earthquake? 2. What is the most common cause of an earthquake? 3. What causes plates to move? 4. What does it take in order for the plates to move? 5. What is released when the plates move? 6. Where do most major earthquakes occur? 7. List three other possible causes for earthquakes., 8. What is the name of the giant waves generated by earthquakes? 9. Why is it important to understand the cause and possible location of earthquakes? Page 2 ESworkbooks 2011cdunbar
Laboratory Activity 5.1 Locations of Earthquakes and Volcanoes [40] Introduction: Scientists have found a pattern of where major earthquakes and volcanoes are located. The map shows where some of Earth s earthquakes and volcanoes are. See if you can find a correlation. Objective: Materials ESRT s Highlighter Color pencils Red pen To determine where most earthquakes, mountain ranges and volcanoes are located Procedure: 1. The map below illustrates locations of earthquakes and active volcanoes. Find as many volcanoes as you can and color them red. 2. Using the reference tables as a guide, label the following plates using red ink. Eurasian Plate (2 places) Antarctic Plate (2 places) African Plate Pacific Plate South American Plate Philippine Plate Indian Australia Plate North American Plate Nazca Plate 3. Find, circle and label the Hawaiian Hot Spot. Guided Inquiry: Earthquakes Page 3
1. The location where the actual movement of plates takes place is called the focus. The depth of the focus changes depending on the plates involved. Using a red color pencil, draw an arrow on the diagram to the right that shows the ocean plate is being subducted. What happens to the depth of the focus as you move to the right of the subduction zone? 2. Using the diagram below, draw a profile for line A, B, C, D on the graph provided. a. Place a scrap paper under the profile line. b. Mark and label the depth of where each letter is located. Page 4 ESworkbooks 2011cdunbar
Distance below surface of ocean (km) c. Place your scrap paper on the graph provided and mark the depth of each location. d. Draw a dark thick line connecting each of the four points. e. Draw two arrows on the graph below to illustrate the movement of plates at the boundary. Draw an additional arrow under the line on the left to show the motion of the ocean plate. 0 100 200 300 400 500 Oceanic Crust Cross-section of South America Continental Crust Check Point 1. What type of boundary is illustrated in the diagram on page 4? 2. Referring to the graph above, which plate is being subducted? 3. In reference to plate boundaries, where are most earthquakes and volcanoes located? 4. Identify the type of plate boundary responsible for the presence of the volcano at location A. 5. Ocean plates are [thicker / thinner] and [ more dense / less dense ] than the continental plates. 6. As you move from west to east along line A, B, C, D what happens to earthquake depth? 7. What is the density of the oceanic plate? (don t forget units) 8. What is the density of the continental plate? (don t forget units) 9. Which plate is subducted continental or oceanic? 10. What land features formed as a result of the oceanic and continental plate collision? and 11. Where are most divergent plate boundaries found? 12. What forms at divergent plates? 13. What type of boundary is the San Andreas fault? 14. At which type of plate boundary is new ocean crust created? 15. Ocean trenches are associated with which type of plate boundary? Guided Inquiry: Earthquakes Page 5
16. Where do most earthquakes occur? 17. Where are most volcanoes found? 18. What is the focus of an earthquake? 19. Describe the movement of each of the boundaries listed below. Name the types of features found at each boundary and give an example of each. Type of boundary Movement of plates (toward, away, slide past) each other Features formed Examples of feature Divergent Convergent Transform Regents Questions: 1. When a continental crustal plate collides with an oceanic crustal plate, the continental crust is forced to move over the oceanic crust. What is the primary reason that the continental crust stays on top of the oceanic crust? (1) Continental crust is less dense. (2) Continental crust deforms less easily. (3) Continental crust melts at higher temperatures. (4) Continental crust contains more mafic minerals. 2. Which coastal area is most likely to experience a severe earthquake? (1) east coast of North America (3) west coast of Africa (2) east coast of Australia (4) west coast of South America 3. According to tectonic plate maps, New York State is presently located (1) at a convergent plate boundary (3) above a mid-ocean ridge (2) above a mantle hot spot (4) near the center of a large plate Page 6 ESworkbooks 2011cdunbar
4. Convection currents in the plastic mantle are believed to cause divergence of lithospheric plates at the (1) Peru-Chile Trench (3) Canary Islands Hot Spot (2) Mariana Trench (4) Iceland Hot Spot Base your answers to questions 5 through 8 on the map below, which shows the location of the Peru- Chile Trench. 5. The Peru-Chile Trench marks the boundary between the (1) Pacific Plate and the Antarctic Plate (2) Nazca Plate and the South American Plate (3) North American Plate and the Cocos Plate (4) Caribbean Plate and the Scotia Plate 6. Which observation provides the best evidence of the pattern of crustal movement at the Peru - Chile Trench? (1) the direction of flow of warm ocean currents (2) the mineral composition of samples of mafic mantle rock (3) comparison of the rates of sediment deposition (4) the locations of shallow-focus and deepfocus earthquakes 7. In which diagram do the arrows best represent the motions of Earth s crust at the Peru- Chile Trench? 8. Which type of crustal plate boundary is shown in this diagram? (1) divergent (2) convergent (3) universal (4) transform Guided Inquiry: Earthquakes Page 7
Mini Lesson 2: P & S Waves There are two main types of waves generated by earthquakes. The first are compression waves generally called P- waves. P-waves move in a back and forth motion and travel in a more direct pattern. They can go through any material and their speed is about twice as fast as S- waves. S-waves, also known as shear waves, travel perpendicular to the direction of plate movement and cannot travel through liquids. Seismographs are instruments used to measure the magnitude of earthquakes. They record the arrival time of the P-waves and S-waves. By using the difference in travel time of these waves scientists are able to determine the distance to an epicenter (location on Earth s surface directly above the focus). In order to determine the epicenter of an earthquake a minimum of 3 seismograph stations must be used. Need to know: Fill in the chart by choosing the answer in the parenthesis that best fits each type of wave. Place the answer on the line provided under the correct wave type. 1. Direction of movement (back and forth or perpendicular) 2. Rate of travel: (fastest or half the speed) 3. Travels through (solid, liquid, gas or does not travel through liquid) P-waves (compresson / primary waves) S-waves (shear / secondary waves) a. a. b. b c. c. 4. Which wave reaches a seismograph station first? 5. What does a seismograph measure? 6. What do seismographs record? 7. What can be determined using the difference in travel time of earthquake waves? 8. What is the minimum number of seismograph stations needed to locate an epicenter? Page 8 ESworkbooks 2011cdunbar
Interpreting the Earthquake P-wave and S-wave Travel Time Chart ESRT pg 11 1. Find the Earthquake P-Wave and S-Wave Travel Time graph on page 11 of the Earth Science Reference Tables. 2. Highlight the label on the bottom of the graph. 3. What is the label on the bottom of the graph? 4. What are the units? 5. Next to the label at the bottom of the graph it states (x 10 3 km). This means that when the number on the bottom of the graph says 1, what is the actual value? 6. Next to each number on the bottom of the chart add three zeros at the end. In other words, the number 1 becomes 1000. 7. What is the value of each smaller division on the bottom of the graph worth? 8. Highlight the label on the left of the graph. 9. What is the label on the left side of the graph? 10. What are the units? 11. What is the value of each smaller division on the side of the graph worth? 12. Trace the line for the P wave in blue and the line for the S wave in orange. A. Determining travel time: Example: How long does it take a P-wave to travel 2,000 km? a) Place straight piece of scrap paper vertically just to the right of the 2,000 km line, starting at the bottom. b) Where the P-wave curve crosses the scrap paper, follow the horizontal line to the left. This will give you the travel time. c) Answer the question. How long does it take a P-wave to travel 2,000 km? min sec Answer the following questions. Make sure you pay attention to which wave (P or S) you need to follow. a) How long does it take an S-wave to travel 7,000 km? min sec b) How long does it take a P-wave to travel 3,900 km? min sec c) How long does it take an S-wave to travel 1,600 km? min sec d) How long does it take a P-wave to travel 8,200 km? min sec e) How long does it take an S-wave to travel 2,100 km? min sec f) How long does it take a P-wave to travel 4,500 km? min sec Guided Inquiry: Earthquakes Page 9
B. Determining distance: Example: How far can an S-wave travel in 11 minutes 00 seconds? a) Place the scrap paper just above the 11 minute line, starting at the left. b) Where the S-wave crosses the scrap paper, go straight down. This will give you distance. c) Answer the question: How far can an S-wave travel in 11 minutes 00 seconds? Answer the following questions. Make sure you pay attention to which wave you need to follow. Regents Questions: a) How far can a P-wave travel in 12 minutes 00 seconds? km b) How far can an S-wave travel in 9 minutes 40 seconds? km c) How far can a P-wave travel in 4 minutes 20 seconds? km d) How far can an S-wave travel in 6 minutes 20 seconds? km e) How far can a P-wave travel in 8 minutes 30 seconds? km f) How far can an S-wave travel in 5 minutes 50 seconds? km 1. How long would it take for the first S-wave to arrive at a seismic station 4,000 kilometers away from the epicenter of an earthquake? (1) 5 min 40 sec (2) 7 min 0 sec (3) 12 min 40 sec (4) 13 min 20 sec km 2. Approximately how long does an earthquake P-wave take to travel the first 6500 kilometers after the earthquake occurs? (1) 6.5 min (2) 8.0 min (3) 10.0 min (4) 18.5 min 3. 12 A P-wave takes 10 minutes and 20 seconds to travel from the epicenter of an earthquake to a seismic station. Approximately how far is the station from the epicenter? (1) 6900 km (2) 5900 km (3) 3100 km (4) 4000 km 4. 12 A S-wave takes 12 minutes and 40 seconds to travel from the epicenter of an earthquake to a seismic station. Approximately how far is the station from the epicenter? (1) 9600 km (2) 3200 km (3) 6000 km (4) 4000 km 5. 12 A P-wave takes 8 minutes and 20 seconds to travel from the epicenter of an earthquake to a seismic station. Approximately how long will an S-wave take to travel from the epicenter of the same earthquake to this seismic station? (1) 6 min 40 sec (2) 9 min 40 sec (3) 15 min 00 sec (4) 19 min 00 sec 6. The epicenter of an earthquake is located 2,800 kilometers from a seismic station. Approximately how long did the S-wave take to travel from the epicenter to the station? (1) 11 min 15 sec (2) 9 min 35 sec (3) 5 min 20 sec (4) 4 min 20 sec Page 10 ESworkbooks 2011cdunbar
7. A S-wave takes 9 minutes and 00 seconds to travel from the epicenter of an earthquake to a seismic station. Approximately how long did the P-wave take to travel from the epicenter of the same earthquake to this seismic station? (1) 6 min 40 sec (2) 4 min 40 sec (3) 5 min 00 sec (4) 12 min 00 sec C. Determining arrival time difference of P-waves and S-waves: Highlight the space between the P-wave and the S-wave on the travel time chart on page 11 of the Earth Science reference tables. This shows the time difference in arrival times for a certain distance. Example: What is the difference in arrival time if the distance is 8,000 km? a) Find the distance for 8,000 km on the bottom of the chart. b) Place a scrap paper vertically (up and down) on the line for that distance. c) Mark where the P-wave touches the scrap paper and label it P. d) Mark where the S-wave touches the scrap paper and label it S. e) Move the paper to the left, bottom of the chart. Place the mark for the P-wave at zero, go up to the S-wave mark and read the time. f) Answer the question: What is the difference in arrival time is the distance is 8,000 km? min sec Answer the following questions. a) What is the difference in arrival time if the distance is 5,200 km? min sec b) What is the difference in arrival time if the distance is 9,600 km? min sec c) What is the difference in arrival time if the distance is 400 km? min sec d) What is the difference in arrival time if the distance is 6,400 km? min sec e) What is the difference in arrival time if the distance is 3,200 km? min sec f) What is the difference in arrival time if the distance is 4,400 km? min sec Regents Questions: 8. A seismic station is recording the seismic waves produced by an earthquake that occurred 4200 kilometers away. Approximately how long after the arrival of the first P-wave will the first S-wave arrive? (1) 1 min 05 sec (2) 5 min 50 sec (3) 7 min 20 sec (4) 13 min 10 sec 9. The first S-wave arrived at a seismograph station 11 minutes after an earthquake occurred. How long after the arrival of the first P-wave did this first S-wave arrive? (1) 3 min 15 s (2) 4 min 55 s (3) 6 min 05 s (4) 9 min 00 s Guided Inquiry: Earthquakes Page 11
D. Determining arrival times Example: A seismic station 4000 kilometers from the epicenter of an earthquake records the arrival time of the first P-wave at 10:00:00. At what time did the first S-wave arrive at this station? a) Find 4000 km at the bottom of the chart. b) What is the time difference between the P and S waves at this distance? c) What time did the P wave arrive? d) How much later did the S wave arrive? (time difference) e) Add the time difference to the arrival time of the P wave then answer the question: f) Answer the question: At what time did the first S-wave arrive at this station? Regents Questions: 10. An earthquake s first P-wave arrives at a seismic station at 12:00:00. This P-wave has traveled 6000 kilometers from the epicenter. At what time will the first S-wave from the same earthquake arrive at the seismic station? (1) 11:52:20 (2) 12:07:40 (3) 12:09:20 (4) 12:17:00 11. An earthquake s first S-wave arrives at a seismic station at 3:36:55. This S-wave has traveled 3200 kilometers from the epicenter. At what time did the first P-wave from the same earthquake arrive at the seismic station? (1) 3:41:30 (2) 3:15:20 (3) 3:32:15 (4) 3:52:40 E. Determining the distance to an epicenter: In order to determine the distance to an epicenter you must know the differences in P-waves and S-waves arrival times at a given seismograph station. Example: How far away is the distance to an epicenter if the difference in arrival time is 3 minutes and 20 seconds? a) Place a scrap paper on the left side of the chart b) Mark the zero and label it P. c) Place a mark at 3 minutes and 20 seconds and label it S d) Keep the paper vertical and move it to the right until the S mark is touching the S-wave line and the P mark is touching the P-wave line. e) Follow the scrap paper down and read the distance at the bottom of the graph. This is the distance to the epicenter. f) Answer the question: How far away is the distance to an epicenter if the difference in arrival time is 3 minutes and 20 seconds? km Page 12 ESworkbooks 2011cdunbar
Answer the following question for each of the following arrival time differences. Regents Questions: How far away is the distance to an epicenter if the difference in arrival time is... a) 5 minutes 20 seconds km b) 6 minutes 00 seconds km c) 10 minutes 20 seconds km d) 1 minute 40 seconds km e) 8 minutes 40 seconds km 12. An earthquake s P-wave arrived at a seismograph station at 02 hours 40 minutes 00 seconds. The earthquake s S-wave arrived at the same station 2 minutes later. What is the approximate distance from the seismograph station to the epicenter of the earthquake? (1) 1,100 km (2) 2,400 km (3) 3,100 km (4) 4,000 km E. Determining the distance to an epicenter when arrival times are given. Example: A seismic recording station recorded an earthquakes P-wave at 1:00:20. The S-wave arrived shortly after at 1:04:40. How far away is the epicenter from this seismic recording station? a) Subtract the P-wave arrival time from the S-wave arrival time S wave arrival time : : P wave arrival time - : : Difference : : b) Using the procedure on page 7 determine the distance to the epicenter. km Answer the following questions: 1) A seismic recording station recorded an earthquake s P-wave at 1:15:30. The S-wave arrived shortly after at 1:19:50. How far away is the epicenter from this seismic recording station? S wave arrival time : : P wave arrival time - : : Difference : : Distance to the epicenter km Guided Inquiry: Earthquakes Page 13
2) A seismic recording station recorded an earthquake s P-wave at 3:25:00. The S-wave arrived shortly after at 3:33:40. How far away is the epicenter from this seismic recording station? S wave arrival time : : P wave arrival time - : : Difference : : Distance to the epicenter km 3) A seismic recording station recorded an earthquake s P-wave at 12:08:30. The S-wave arrived shortly after at 12:15:30. How far away is the epicenter from this seismic recording station? S wave arrival time : : P wave arrival time - : : Difference : : Distance to the epicenter km 4) A seismic recording station recorded an earthquake s P-wave at 9:20:05. The S-wave arrived at 9:30:45. How far away is the epicenter from this seismic recording station? S wave arrival time : : P wave arrival time - : : Difference : : Distance to the epicenter km If the S-wave arrival time minutes or seconds are less than the P- wave s, you will need to borrow time. REMEMBER: There are 60 seconds in a minute and 60 minutes in an hour. d) A seismic recording station recorded an earthquake s P-wave at 03:59:40. The S-wave arrived shortly after at 04:05:40. How far away is the epicenter from this seismic recording station? S wave arrival time : : P wave arrival time - : : Difference : : Distance to the epicenter km Page 14 ESworkbooks 2011cdunbar
Laboratory Activity 5.2 Reading Seismograms and Locating an Epicenter [40] Introduction: There are seismic stations located all over the world. Each small movement of Earth s crust can result in many of these stations recording at least some type of data (P wave and S wave arrivals) that assist in determining where the epicenter is located. The minimum number of seismic stations necessary to locate an epicenter is three (3). Objective: Materials Earth Science Reference Table Compass Determine the distance to the epicenter Locate the epicenter using the data given and a drawing compass Procedure A: Reading Seismograms 1. The diagrams that follow represent three seismograms showing the same earthquake as it was recorded at three different seismic stations, A, B and C. 2. On the seismogram to the right, draw an arrow from the letter P on the seismogram straight down to the time marker. 3. What time did the P-wave arrive at Station A? : : 4. Draw an arrow from the letter S on the seismogram straight down to the time marker. 5. What time did the S-wave arrive at Station A? : : 6. What is the arrival time difference? min sec 7. When using a seismograph it is often possible to determine the arrival time difference between the P-wave and S-wave by simply counting. How many minutes does each small line on Station A represent? 8. Place your pen on the time where the P arrow is on the bottom of the chart. Count over the number of marks until you get to the arrow that represents the S arrival. 9. What is the arrival time difference? min sec 10. Using the Earthquake P-wave and S-wave Travel Time graph on page 11 of the Earth Science Reference Tables, determine the distance to the epicenter. km 11. On the seismogram to the right, draw an arrow from the letter P and S on the seismogram straight down to the time marker. 12. What time did the P-wave arrive at Station B? : : 13. What time did the S-wave arrive at Station B? : : Guided Inquiry: Earthquakes Page 15
14. What is the arrival time difference? min sec 15. What is the arrival time difference? (just count) min sec 16. What is the distance to the epicenter? km 17. On the seismogram above labeled Station C, draw an arrow from the letter P on the seismogram straight down to the time marker. 18. What time did the P-wave arrive at Station C? : : 19. Draw an arrow from the letter S on the seismogram straight down to the time marker. 20. What time did the S-wave arrive at Station C? : : 21. What is the arrival time difference? (just count) min sec 22. What is the distance to the epicenter? km 23. Fill in the chart below using the data you interpreted in previous questions. Seismogram P-wave arrival time S-wave arrival time Difference in arrival times Distance to the epicenter Station A : : : : min sec km Station B : : : : min sec km Station C : : : : min sec km 24. Which station (A, B or C) had the P-wave arrive first? 25. Which station (A, B or C) had the shortest difference in arrival times? 26. Which station (A, B or C) is the closest distance to the epicenter? 27. List the two ways to determine which station is closest to the epicenter. 28. List the two ways to determine which station is farthest from the epicenter. Page 16 ESworkbooks 2011cdunbar
Procedure B: Locating an Epicenter Carefully remove the last page of this packet (page 33). It has an enlarged chart so that it will be easier to estimate the distance to an epicenter for the locations on pages 18-21. 1. The distance from Sacramento, CA to the epicenter is 650 km. Place the compass point on zero of the map scale below and the pencil point on 650 km. 2. Take the compass point and place it on Sacramento and draw a circle. 3. The distance from Atlanta, GA to the epicenter is 875 km. Place the compass point on zero of the map scale below and the pencil point on 875 km (estimate). 4. Take the compass point and place it on Atlanta and draw a circle. 5. The distance from Topeka, KS to the epicenter is 375 km. Place the compass point on zero of the map scale below and the pencil point on 375 km (estimate). 6. Take the compass point and place it on Topeka and draw a circle. 7. The epicenter is located where all three circles intersect. 8. What city on the map is the epicenter closest to? Sacramento Olympia Salem Carson City Boise Helena Salt Lake City Phoenix Cheyenne Denver Santé Fe Bismarck Pierre Lincoln Topeka Oklahoma City Austin St. Paul Des Moines Jefferson City Little Rock Baton Rouge Madison Springfield Lansing Indianapolis Nashville Columbus Frankfort Atlanta Jackson Montgomery Charleston Montpellier Harrisburg Raleigh Columbia Tallahassee Albany Richmond Augusta Concord Boston Providence Hartford Trenton Dover Annapolis Washington DC Map Scale km 0 200 400 600 800 1000 Guided Inquiry: Earthquakes Page 17
5:04:00 5:05:00 5:06:00 5:07:00 5:08:00 5:09:00 5:04:00 5:05:00 5:06:00 5:07:00 5:08:00 5:09:00 5:04:00 5:05:00 5:06:00 5:07:00 5:08:00 5:09:00 9. The diagrams below represent three seismographs showing the same earthquake as it was recorded at three different seismic stations. Determine the time difference and distance to the earthquake for each location. Use arrows and remember to count. City Arrival time difference Distance to epicenter Sacramento, CA P S Sacramento min sec km Little Rock min sec km Bismarck min sec km (a) Starting with Sacramento, construct a circle to illustrate the distance to the epicenter. (b) Construct a circle for each of the other locations. (c) Place an X in the center where the circles intersect. (d) What is the name of the city where the epicenter is located? Little Rock, AR Bismarck, ND P P S S Sacramento Olympia Salem Carson City Boise Helena Salt Lake City Phoenix Cheyenne Denver Santé Fe Bismarck Pierre Lincoln Topeka Oklahoma City Austin St. Paul Des Moines Jefferson City Little Rock Baton Rouge Madison Springfield Lansing Indianapolis Nashville Columbus Frankfort Atlanta Jackson Montgomery Charleston Harrisburg Raleigh Montpellier Columbia Tallahassee Albany Richmond Augusta Concord Boston Providence Hartford Trenton Dover Annapolis Washington DC Map scale km 0 200 400 600 800 1000 Page 18 ESworkbooks 2011cdunbar
23: 53:00 23:54:00 23:55:00 23:56:00 23:57:00 23:58:00 23: 53:00 23:54:00 23:55:00 23:56:00 23:57:00 23:58:00 23: 53:00 23:54:00 23:55:00 23:56:00 23:57:00 23:58:00 10. The diagrams below represent three seismographs showing the same earthquake as it was recorded at three different seismic stations. Determine the time difference and distance to the earthquake for each location. Use arrows and remember to count. City Arrival time difference Distance to epicenter Phoenix, AZ P S Phoenix min sec km Bismarck min sec km Topeka min sec km (a) Starting with Phoenix, construct a circle to illustrate the distance to the epicenter. (b) Construct a circle for each of the other locations. (c) Place an X in the center where the circles intersect. (d) What is the name of the city where the epicenter is located? Bismarck, ND Topeka, KS P S P S Olympia Helena Bismarck St. Paul Albany Des Moines Sacramento Salt Lake City Denver Topeka Springfield Frankfort Phoenix Santé Fe Oklahoma City Little Rock Columbia Jackson Montgomery Map scale km 0 200 400 600 800 1000 Guided Inquiry: Earthquakes Page 19
8:10:00 8:11:00 8:12:00 8:13:00 8:14:00 8:15:00 8:10:00 8:11:00 8:12:00 8:13:00 8:14:00 8:15:00 8:10:00 8:11:00 8:12:00 8:13:00 8:14:00 8:15:00 11. The diagrams below represent three seismographs showing the same earthquake as it was recorded at three different seismic stations. Determine the time difference and distance to the earthquake for each location. Use arrows and remember to count. City Arrival time difference Distance to epicenter Helena, MT P S Helena min sec km Frankfort min sec km Sacramento min sec km a) Starting with Helena, construct a circle to illustrate the distance to the epicenter. b) Construct a circle for each of the other locations. c) Place an X in the center where the circles intersect. d) What is the name of the city where the epicenter is located? Frankfort, KT Sacramento, CA P P S S Olympia Helena Bismarck St. Paul Albany Des Moines Sacramento Salt Lake City Denver Topeka Springfield Frankfort Phoenix Santé Fe Oklahoma City Little Rock Columbia Jackson Montgomery Map scale km 0 200 400 600 800 1000 Page 20 ESworkbooks 2011cdunbar
12:15:00 12:16:00 12:17:00 12:18:00 12:19:00 12:20:00 12:15:00 12:16:00 12:17:00 12:18:00 12:19:00 12:20:00 12:15:00 12:16:00 12:17:00 12:18:00 12:19:00 12:20:00 12. The diagrams below represent three seismographs showing the same earthquake as it was recorded at three different seismic stations. Determine the time difference and distance to the earthquake for each location. Use arrows and remember to count. City Arrival time difference Distance to epicenter Montgomery, AL P S Montgomery min sec km Albany min sec km Oklahoma City min sec km a) Starting with Montgomery, construct a circle to illustrate the distance to the epicenter. b) Construct a circle for each of the other locations. c) Place an X in the center where the circles intersect. d) What is the name of the city where the epicenter is located? Albany, NY Oklahoma City, OK P P S S Olympia Helena Bismarck St. Paul Albany Des Moines Sacramento Salt Lake City Denver Topeka Springfield Frankfort Phoenix Santé Fe Oklahoma City Little Rock Jackson Montgomery Map Scale km 0 200 400 600 800 1000 Guided Inquiry: Earthquakes Page 21
Regents Question: The diagram shows three seismograms of the same earthquake recorded at three different seismic stations, X, Y, and Z. Using the information on the diagram, fill in the table below. NOTE: Instead of subtracting just COUNT. Place all of the answers to the following questions in the table below. - Determine the following (a) the difference in arrival time for each location. (b) the distance to the epicenter. (c) the travel time of P and S waves. DO NOT write down arrival times. Station X Station Y Station Z Difference in arrival time min sec min sec min sec Distance to the epicenter km km km P-wave travel time min sec min sec min sec S-wave travel time min sec min sec min sec The distances from each seismic station to the earthquake epicenter have been drawn on the map to the right. A coordinate system has been placed on the map to describe locations. The map scale has not been included. 1. In the three boxes provided, label the location of each seismograph station using the corresponding letters, X, Y and Z. 2. Which location is closest to the epicenter? (1) E-5 (2) G-1 (3) H-3 (4) H-8 Explain your reasoning. 3. State two ways in which you can determine which seismograph station was the closest to an epicenter if you were not provided with a time scale on the bottom of the graph. Page 22 ESworkbooks 2011cdunbar
4. A minimum of seismic stations are needed to locate an earthquake epicenter. - One seismic station gives you only, and NOT direction - Two stations may give you possible locations where the two circles intersect - When stations are used, the epicenter is where they all a. Which seismic station is closest to the epicenter? A C B b. How can you tell by the diagram? Which seismic station is farthest away from the epicenter? How can you tell by the diagram? c. Describe where the epicenter is. d. Place an X at the epicenter. 5. Through which materials can P-waves travel? (1) Solid rock, only (2) Solid rock, magma, water, and natural gas X (3) Magma, water, and natural gas only (4) Magma and water, only 6. Earthquake S-waves do not travel through the Earth s (1) crust (2) moho (3) mantle (4) core 7. What is the total distance that a P-wave will travel in 7 minutes and 20 seconds? (1) 2,000 km (2) 5,800 km (3) 4,200 km (4) 7,200 km 8. In 8 minutes, an earthquake P-wave travels a total distance of (1) 2,100 km (2) 4,700 km (3) 6,600 km (4) 11,300 km 9. Approximately how far away from the receiving station is the epicenter of an earthquake if the difference in arrival times of P and S waves at the station is 6 minutes and 30 seconds? (1) 3,000 km (2) 5,000 km (3) 6,300 km (4) 8,000 km 10. A seismograph indicates the difference between the arrival of S-waves and P-waves to be 4 minutes. The distance of the seismograph station from the earthquake s epicenter is about (1) 1,000 km (2) 1,500 km (3) 2,000 km (4) 2,500 km Guided Inquiry: Earthquakes Page 23
11. The epicenter of an earthquake is located near Massena, New York. The greatest difference in arrival times of the P- and S-waves for this earthquake would be recorded in (1) Plattsburg, New York (3) Albany, New York (2) Binghamton, New York (4) Utica, New York 12. The seismograph to the right shows the arrival times of P-wave and S- waves from a single earthquake. How far from the earthquake epicenter was the station that recorded this seismogram? (1) 1.5 x 10 3 km (3) 7.5 x 10 3 km (2) 4.0 x 10 3 km (4) 2.6 x 10 3 km 13. At a seismograph recording station, the difference between the arrival times of an earthquake s compression wave (P-wave) and its shear wave (S-wave) is 8 minutes 20 seconds. How far from the station is the epicenter? (1) 2,400 km (2) 4,500 km (3) 5,000 km (4) 6,800 km 14. What is the approximate difference in arrival times of the P-waves and the S-waves at a seismographic station that is 3,000 kilometers from an earthquake epicenter? (1) 2 min 15 sec (2) 3 min 40 sec (3) 4 min 30 sec (4) 5 min 40 sec 15. The circles on the map to the right show the distances from three seismic stations, X, Y and Z, to the epicenter of an earthquake. Which location is closest to the earthquake epicenter? (1) A (2) B (3) C (4) D 16. The S-waves from an earthquake that travel toward Earth s center will (1) be deflected by Earth s magnetic field (2) be totally reflected off the crust-mantle interface (3) be absorbed by the liquid outer core (4) reach the other side of Earth faster than those that travel around Earth in the crust 17. The seismogram to the right shows P- wave and S-wave arrival times at a seismic station following an earthquake. The distance from this seismic station to the epicenter of the earthquake is approximately (1) 1,600 km (3) 4,400 km (2) 3,200 km (4) 5,600 km Page 24 ESworkbooks 2011cdunbar
Show what you know: Measuring an Earthquake There are two basic scales which scientists use to measure an earthquake, the Richter scale and the Mercalli Scale. The Richter scale uses seismographs and measures an earthquake s magnitude. Each successive number is ten times greater than the previous. For example a magnitude of 4 is ten times greater than a magnitude of 3. The seismometer moves as Earth shakes. The heavy mass does not move. The recording device measures how far the rest of the seismometer has moved with respect to the mass. Richter Increase in number Magnitude 1 1 2 10 3 100 4 1,000 5 10,000 6 100,000 7 1,000,000 8 10,000,000 9 100,000,000 The Mercalli scale measures an earthquake s intensity and is based on reports from people who experienced the event. This scale is subjective because it relies on peoples interpretation. Modified Mercalli Scale Intensity I II III IV V VI VII VIII IX X XI XII Observed Effects Felt by only a few people under very special circumstances Felt by only a few people at rest, especially on the upper floors of buildings Felt noticeably indoors, especially on upper floors of buildings Felt indoors by many people, outdoors by a few; some awaken Felt by nearly everyone; many awaken; dishes and windows break; plaster cracks Felt by everyone; many frightened and run outdoors; heavy furniture moves Everyone runs outdoors; slight to moderate damage in ordinary structures Considerable damage in ordinary structures; chimneys and monuments fall Considerable damage in all structures; ground cracks; underground pipes break Most structures destroyed; rails bend; landslides occur; water splashes over banks Few structures left standing; bridges destroyed; broad fissures in the ground; underground pipes break Damage total; waves seen on ground surfaces; objects thrown in air Guided Inquiry: Earthquakes Page 25
Procedure: Below is an example of a seismogram and set of instructions for determining the Richter magnitude of an earthquake below. The example shows the Richter magnitude of an earthquake that occurred 210 kilometers from a seismic station. Instructions for determining Richter magnitude: Determine the distance to the epicenter of the earthquake. The distance in the example is 210 kilometers. Highlight the location at 210 km on the diagram above. 1. Measure the maximum wave height of the S-wave recorded on the seismogram. Look at the top right of the diagram. Notice how they determined the height in the example (23 millimeters). Highlight the height of the largest S-wave on the diagram above. 2. Place a straight edge between the distance to the epicenter (210 kilometers) and the height of the largest S-wave (23 millimeters) on the appropriate scales. Highlight the line connecting these two points. 3. The magnitude of the earthquake is determined by where the line intersects the Richter magnitude scale. The magnitude of this example is 5.0. Circle the number 5 in the diagram above. Page 26 ESworkbooks 2011cdunbar
4. Using the set of instructions on page 26 and the seismogram and scales below, determine the Richter magnitude of an earthquake that was located 500 kilometers away. a. What is the distance to the epicenter? b. What is the highest height of the earthquake S-wave? c. Draw a line connecting those two values. d. What is the Richter magnitude of this earthquake? 5. Identify the information shown on the seismogram that was used to determine that the distance to the epicenter was 500 kilometers. 6. How long did it take the first S-wave to travel 500 kilometers to reach this seismic station? min sec Guided Inquiry: Earthquakes Page 27
Base your answers to questions 7 through 11 on the Earth Science Reference Tables, the map below, and table of the Modified Mercalli Scale on page 25. The map shows the intensities of the earthquake that occurred slightly southwest of New Madrid, Missouri, on December 16, 1811. The numbered areas on the map were determined from the Modified Mercalli Scale according to the observed effects of the earthquake. 7. 8. 9. What is the approximate location of the earthquake s epicenter? (1) 36 N, 90 W (2) 90 N, 36 W (3) 36 N, 90 E (4) 90 N, 36 E Using the Mercalli scale on page 17, which city would have issued the report: Heavy furniture moved, everyone felt the earthquake, and many people were frightened and ran outdoors? (1) Cincinnati (2) Pittsburgh (3) Syracuse (4) Boston What was the approximate travel time for the earthquake s P-wave from the epicenter to Syracuse, New York? (1) 1 min (2) 5 min (3) 3 min (4) 10 min 10. For which city was the difference in arrival times between P-waves and S-waves the greatest? (1) Nashville (2) Pittsburgh (3) Syracuse (4) Boston 11. Which statement best describes the earthquake waves recorded at Louisville? (1) S- waves arrived ahead of P-waves. (3) S-waves arrived but P-waves did not (2) Neither S-waves nor P-waves arrived (4) P-waves arrived ahead of S-waves Page 28 ESworkbooks 2011cdunbar
Show what you know: Shadow Zone As P-waves and S-waves pass through different layers within Earth s interior they are refracted (bent) due to differences in density. Some areas on Earth s surface only receive P-waves, because S-waves can only travel through solids and the outer core is liquid. Other sections on Earth s surface receive no earthquake waves because of the way the waves bend within the Earth. These areas are known as the shadow zone. Regents Questions 1. An earthquake s P-wave arrived at a seismograph station at 02 hours 40 minutes 00 seconds. The earthquake s S-wave arrived at the same station 2 minutes later. What is the approximate distance from the seismograph station to the epicenter of the earthquake? (1) 1,100 km (2) 2,400 km (3) 3,100 km (4) 4,000 km 2. An earthquake recorded by seismic stations around the world created the pattern of seismic wave recordings shown in the diagram below. Which statement best explains this pattern of wave recordings? (1) Some seismic waves cannot travel through oceans to reach every location on Earth. (2) S-waves are too weak to travel very far from the earthquake focus. (3) Mountain ranges and tectonic plate boundaries absorb or bend seismic waves (4) Layers with different properties inside Earth absorb or bend seismic waves. Earthquake focus No seismic waves recorded Both P- and S- waves recorded 105 140 Only P-waves recorded 3. An earthquake s magnitude can be determined by (1) analyzing the seismic waves recorded by a seismograph (2) calculating the depth of the earthquake faulting (3) calculating the time the earthquake occurred (4) comparing the speed of P-waves and S-waves Guided Inquiry: Earthquakes Page 29
4. Which statement about earthquake waves best supports the inference that the Earth s outer core is liquid? (1) The velocity of earthquake waves increases as the distance from an epicenter increases. (2) The difference in arrival times for compressional and shear waves increases as the distance from an epicenter increases. (3) Compressional waves travel faster than shear waves. (4) Shear waves travel only through solids. 5. The theory that the outer core of the Earth is composed of liquid material is best supported by (1) seismic studies which indicate that shear waves do not pass through the outer core (2) seismic studies which show that compressional waves can pass through the outer core (3) gravity studies which indicate that gravitational strength is greatest within the core (4) density studies which show that the outer core is slightly more dense than the inner core 6. A seismogram recorded at a seismic station is shown to the right. Which information can be determined by using this seismogram? (1) the depth of the earthquake s focus (2) the direction to the earthquake s focus (3) the location of the earthquake s epicenter (4) the distance to the earthquake s epicenter Base your answers to questions 7 and 8 on the diagram below, which represents seismic stations A, B, and C. The distance from each station to an earthquake s epicenter is plotted. 7. The P-wave of an earthquake originating 2,600 kilometers from seismic station A arrived at 5:24:45 a.m. What was the arrival time of the S-wave from the same earthquake? (1) 1:24:45 a.m. (3) 5:28:45 a.m. (2) 5:21:05 a.m. (4) 9:24:05 a.m. 8. The epicenter is closest to point (1) D (2) F (3) E (4) G Page 30 ESworkbooks 2011cdunbar
9. Which generalization about earthquake S-waves and P-waves is correct? (1) S-waves always travel about twice as fast as P-waves (2) The velocity of P-waves and S-waves is constant, regardless of the distance traveled. (3) P-waves always travel faster than S-waves regardless of the distance traveled. (4) When the P-waves and S-waves are near the epicenter, they both travel at the same speed. Base your answers to questions 10 and 11 on the map below. Seismic stations are located at the four cities shown on the map. Letter X represents the epicenter of an earthquake determined from seismic waves recorded at all four cities. 10. Which map correctly shows how the location of the epicenter was determined? 11. At which city is there a difference of approximately 3 minutes and 20 seconds between the arrival times of the P-waves and the S-waves? (1) New Orleans (3) Pittsburgh (2) Louisville (4) New York City 12. Approximately how long does an earthquake P-wave take to travel the first 6500 kilometers after the earthquake occurs? (1) 6.5 min (2) 8.0 min (3) 10.0 min (4) 18.5 min Guided Inquiry: Earthquakes Page 31
13. The map to the right shows the location of an earthquake epicenter in New York State. Seismic stations A, B, and C received the data used to locate the earthquake epicenter. The seismogram recorded at station A would show the (1) arrival of P-waves, only (2) earliest arrival time of P-waves (3) arrival of S-waves before the arrival of P-waves (4) greatest difference in the arrival times of P-waves and S- waves Base your answers to questions 14 and 15 on the cross-sectional view of Earth below, which shows seismic waves traveling from the focus of an earthquake. Points A and B are locations on Earth s surface. 14. A seismic station located at point A is 5400 kilometers away from the epicenter of the earthquake. If the arrival time for the P-wave at point A was 2:00 p.m., the arrival time for the S-wave at point A was approximately (1) 1:53 p.m. (3) 2:09 p.m. (2) 2:07 p.m. (4) 2:16 p.m. 15. Which statement best explains why only one type of seismic wave was recorded at location B? (1) S-waves cannot travel through the liquid outer core. (2) S-waves cannot travel through the liquid inner core. (3) P-waves cannot travel through the solid outer core. (4) P-waves cannot travel through the solid inner core. 16. According to the Richter scale, an earthquake that measures 4 releases how many times more energy than a quake that measures 3? 17. The scale is used to measure the damage caused by an earthquake. 18. There are certain places on earth that can not record any earthquake waves. This is known as the 19. What evidence do scientists have that indicates Earth has a liquid outer core? Page 32 ESworkbooks 2011cdunbar
Below is a small section taken from the chart on page 11 of the Earth Science Reference Tables. Use this to determine the distances to the epicenters for the seismograph locations on pages 18 through 21. Earthquake P-Wave and S-Wave Travel Time (bottom left of chart) Guided Inquiry: Earthquakes Page 33