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Abstract

Students will learn graphing skills, data interpretation, and earthquake mechanics through the use of the Quake Catcher Network (QCN) device and a gritted surface to demonstrate fault slip.

Introduction

K-12 Earthquake Activity Teaching Modules

A Joint Project of the Network for Earthquake Engineering Simulation (NEES) and the Southern California Earthquake Center (SCEC)

In the spring of 2011, NEES at the University of California Santa Barbara (NEES@UCSB) embarked on a project to develop a comprehensive set of teaching modules for K-12 students that would cover the basics of plate tectonics and earthquake dynamics. The idea for the project grew from the success of the “Make Your Own Earthquake” outreach activity developed by NEES@UCSB, which recently has included the use of the Quake Catcher Network MEMS accelerometer.

The UCSB site received a supplemental grant for Education, Outreach, and Training from NEES that provided funds for an undergraduate student to work on this project. Two NEES REU interns and a SCEC intern were also recruited, for a total of four students working cooperatively on the project over the summer of 2011. NEES@UCSB personnel served as mentors to the students and a Santa Barbara GATE science teacher was hired, through the NEES EOT grant, as a consultant to review the work. The students were asked to incorporate, as appropriate, the use of the QCN accelerometer and real earthquake data in the teaching modules. They were also asked to do a comprehensive survey of earthquake-related teaching materials currently available and to incorporate, with proper references, any of these materials into the new modules.

Over the course of the summer of 2011, the students met weekly with their mentor and the science teacher. In August, a group of local 4th – 6th grade students came to the UCSB campus and tested several of the earthquake activities. The summer interns presented their work at the NEES REU Young Researchers Symposium at UCSB in August and at the annual SCEC meeting in Palm Springs in September.

The 12 earthquake activity modules are summarized below:

Personnel:

Jamison Steidl, Ph.D., Principal Investigator, NEES@UCSB
Sandra Seale, Ph.D., Project Scientist and Outreach Coordinator, NEES@UCSB
Carrie Garner, M.A., Gifted and Talented Education Teacher and Coordinator, Hope School District

Summer Undergraduate Interns:

Sean Allen, Civil Engineering, University of Nevada, Reno
Heidi Pence, Civil Engineering, University of Michigan
Joseph Trudeau, Geology, University of Wisconsin
Hanna Vincent, Mechanical Engineering and Materials, MIT

Earthquake Activity Modules:

9th – 12th Grade: Fault Slip, Joseph Trudeau

[Be sure to click the "Docs and Attachments" tab to view and download attachments for this lesson such as handouts and worksheets.]

Earthquake Engineering Component

Learning Objectives and Standards

Links to the National Science Standards and to individual State Science Standards are available by using this link:

http://nees.org/education/for-teachers/k12-teachers#standards

California state standards satisfied:

Earth Sciences

Dynamic Earth Processes

3. Plate tectonics operating over geologic time has changed the patterns of land, sea, and mountains on Earth’s surface. As the basis for understanding this concept:

d. Students know why and how earthquakes occur and the scales used to measure their intensity and magnitude.

California Geology

9. The geology of California underlies the state’s wealth of natural resources as well as its natural hazards. As a basis for understanding this concept:

b. Students know the principal natural hazards in different California regions and the geologic basis of those hazards.

Investigation and Experimentation

1. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other four strands, students should develop their own questions and perform investigations. Students will:

a. Select and use appropriate tools and technology (such as computer-linked probes, spreadsheets, and graphing calculators) to perform tests, collect data, analyze relationships, and display data.

b. Identify and communicate sources of unavoidable experimental error.

c. Identify possible reasons for inconsistent results, such as sources of error or uncontrolled conditions.

d. Formulate explanations by using logic and evidence.

e. Solve scientific problems by using quadratic equations and simple trigonometric, exponential, and logarithmic functions.

l. Analyze situations and solve problems that require combining and applying concepts from more than one area of science.

Material List

Materials Needed:

  • 4’ long wood 2 x 4.
    • Optional: Multiple boards to test multiple frictional surfaces. If you choose to do this you will also need different grit sandpapers.
  • 6 extra-long rubber bands 7” (18cm). 4 are required and 2 are spares.
  • 2 bricks. 1 for the experiment and 1 is a spare for the additional experiments section.
  • Meter stick. All measurements will be in SI units.
  • Wood glue.
  • Thin cord ~2’ long. Laundry line works.
  • 1 bag of play sand. This will be used to cover the board to create a frictional surface for the brick to slide along.
  • Quake Catcher Network (QCN) Device available at http://qcn.stanford.edu/learning/requests.php#Purchase
  • Computer to attach the QCN device and run the program.
  • Scale to measure the weight of the brick.
  • Optional: Excel software to maintain a spreadsheet of the experiment results.

The materials can be purchased at any hardware store such as Menards, Home Depot, Orchard Supply, etc. The long rubber bands can be purchased at an office supply store and the QCN device can be purchased at the website listed above. Total cost will be approximately $20.

qcn_sensor

Materials Needed for Multiple Groups:

  • 4’ long wood 2 x 4. 1 for each group.
    • Optional: Multiple boards to test multiple frictional surfaces. If you choose to do this you will also need different grit sandpapers.
    • 5 extra-long rubber bands 7” (18cm) for each group. 4 are needed for the experiment and 1 is a spare.
    • 1 brick for each group. Have 1-2 extra bricks in case some break.
      • Optional-2 bricks. 1 brick for the experiment and 1 for the additional experiment section.
      • 1 meter stick per group. All measurements will be in SI units.
      • Wood glue.
      • Thin cord ~2’ long in length per group. Laundry line works.
      • 1 bag of play sand. This will be used to cover the board to create a frictional surface for the brick to slide along.
      • 1 Quake Catcher Network Device (QCN device) per group. Available at http://qcn.stanford.edu/learning/requests.php#Purchase

Procedure

Preparation: (See Figures below for help)

  1. Evenly spread a layer of glue to one side of the 2 x 4 and apply to the full length of the board.
  2. Sprinkle a generous layer of sand over the glue to completely cover the board and let the board sit overnight to let the glue set.
  3. When the glue dries mark the length of the board in centimeters.
  4. Strap 2 rubber bands around the brick like a harness.
  5. Tie 2 rubber bands to the rubber bands around the brick.
  6. Tie the other end of the rubber band a thin cord.
  7. Tape the QCN device to the top center of the brick to record the "earthquakes" produced. The QCN device should be firmly planted so as to not slip. The x-axis marked on the QCN device should be parallel to the length of the brick and the y-axis perpendicular.

Fault_Slip_Figure_1

Figure 1. The bottom board has the glue with sand sprinkled over it. The top board has sandpaper glued to it. This is used in the additional experiments section for comparing slip for the different frictional surfaces.

Fault_Slip_Figure_2

Figure 2. The brick with rubber band harness.

Fault_Slip_Figure_3

Figure 3. The complete set up: brick with QCN device taped to the top, ready to pull.

Overview:

This experiment demonstrates plate tectonics as a mechanism for generating earthquakes and the fact that fault slip is greater when a larger stress is applied to a fault. As tectonic plates are pushed together, they store energy that is released in an earthquake. Rocks that are thought of as rigid objects are in fact somewhat elastic. In this experiment, as the rubber band is stretched, the potential energy builds up and then is released as kinetic energy when the brick slips. Tectonic plates move at millimeters to centimeters a year and potential energy is stored at the major faults. The amount of energy released in a M5.5 earthquake is 1020ergs. The energy released by the 1946 atomic blast at Bikini Atoll was about 1019ergs (Bolt, 1993). An erg is a unit of energy for the work being done by a force of one dyne over a distance of one centimeter. A dyne is the force required to accelerate a mass of 1 gram at a rate of 1 centimeter per second squared (cm/s2). Note that a M5.5 earthquake releases more energy than the 1946 Bikini Atoll atomic bomb.

The brick slipping over a frictional surface represents a fault subject to plate movement in this experiment. The QCN device is an accelerometer and when the fault slips in this experiment, the QCN device records the amplitudes of the accelerations. Acceleration amplitudes are used to determine the magnitude of the quake. The equation for calculating magnitude is complicated and is not included in the exercise, but seeing the amplitude of the accelerations generated by the earthquake gives a sense of the magnitude.

Links and Resources

Vocabulary:

Amplitude (wave): The height of the largest pulse in a wave between its minimum and maximum.

Dependent Variable: The variable being studied and expected to change with the independent variable. It is dependent on the independent variable. It answers the question of what is being observed.

Epicenter: The point on the Earth’s surface above the focus hypocenter.

Fault: A planar break in the rock, along which an earthquake can occur.

Focus or hypocenter: The point below the surface at which an earthquake occurs.

Hypothesis: Derived from the Greek word hypotithenai meaning "to suppose" or "to put under." A hypothesis is a proposed explanation for an observed phenomenon.

Independent Variable: Variable being tested or changed.

Kinetic Energy: The energy an object has due to its motion. A ball on the edge of a table has potential energy. A ball falling off the table has kinetic energy.

Lithosphere: The rigid outermost layer of the earth.

Liquefaction: The process of sand and soil behaving like a dense liquid rather than a solid during an earthquake. Water flows between the pores in the soil to cause this natural phenomenon.

Magnitude: A measure of the size of an earthquake. For every unit magnitude increase, the energy output is about 32 times greater. For an earthquake of M5.5 and another of M6.5, the M6.5 had 32 times the energy released than the M5.5 earthquake.

P and S Waves: Also known as primary and secondary waves. Body waves generated by an earthquake that arrive before the surface waves. The p (pressure) wave travels faster than the s (shear) wave.

Plate Tectonics: A model of the earth's lithosphere being divided into plates that move millimeters to centimeters a year.

Potential Energy: The energy an object has because of its position. A ball on the edge of a table has potential energy. A ball falling off the table has kinetic energy.

Seismogram: The record of ground motion generated by an earthquake.

Seismogram pendulum: Instrument that swings on a single axis to measure the amplitude of the shaking in that direction during an earthquake.

Seismograph: Instrument that records seismic vibrations.

Seismologist: A person who studies earthquakes and the composition of the Earth's interior.

Seismology: The study of earthquakes and the composition of the Earth's interior.

Surface waves: The waves generated from an earthquake that travel along the surface of the Earth, as opposed to body waves, which travel through the Earth. Surface waves travel along the surface of the earth at a slower speed than the S waves. There are two types of surface waves: Rayleigh waves and Love waves.

Seismometer: Mass and transducer inside the seismograph.

Triangulation: The process of finding the epicenter of an earthquake by comparing the distance of the event computed from the records of 3 different seismograph stations.

Tsunami: A long ocean wave usually caused by sea-floor movements from an earthquake. Undersea landslides can also produce tsunamis, but these are usually smaller in scale. When tsunamis occur, they usually arrive in several waves and the first to hit the shore is not necessarily the largest.

Background:

Earthquakes release energy. For every unit increase in magnitude, the energy output is about 32 times greater. If you compare an earthquake of M5.5 and another of M6.5, the M6.5 had 32 times the energy released than the M5.5 earthquake. The amplitudes of the earthquake waves increase by a factor of 10 for each unit increase in magnitude.

In order to get a complete picture of an earthquake, an instrument needs to record motions on 3 axes. Seismographs have three instruments measuring ground motion in the vertical and two horizontal directions. By studying records recorded over a large area, a seismologist can determine the location and the magnitude of the earthquake.

History:

A few examples of historical large earthquakes in the United States are the 1906 San Francisco Earthquake, the 1989 Loma Prieta Earthquake, and the 1964 Prince William Sound Earthquake in Alaska. These quakes demonstrate that the magnitude of the quake is not the only factor in generating damage.

The 1906 San Francisco Earthquake is still under investigation and the magnitude of the quake is disputed. The moment magnitude (Mw) has been estimated at M8.0 (de Boer and Sanders 2005). The casualty report is also debated and the initial report cited only 375 deaths. More recent estimates give a death toll of 2,500 people in the San Francisco area. The fire damaged more property than the quake itself by a factor of 10 (Bolt 1993), (de Boer and Sanders 2005).

The 1989 Loma Prieta event is also called the World Series Earthquake because it took place during the World Series near San Francisco. The casualties in this quake were 63 dead and almost 4,000 injured (Bolt 1993). There were few casualties in this earthquake because at that time of day (early evening), most people were in their homes. Most homes are constructed of wood, which holds up to earthquakes fairly well. The quake had a surface wave magnitude of M7.1 (Bolt 1993).

The 1964 Prince William Sound event in Alaska had 130 casualties, with only 9 being a direct result of the shaking of the earthquake (Bolt 1993). The rest of the damage came from two secondary affects of earthquakes: tsunamis and liquefaction.

Earthquake Prediction:

Why is it that Southern California is in the news all the time talking about the Big One coming? The answer is a matter of probability. California has a 99.7% chance of having a M6.7 or greater earthquake in the next 30 years. The probabilities are different for different sections of the San Andreas Fault (Figures 6 and 7). The San Andreas Fault is a strike-slip fault on the boundary of the Pacific and North American tectonic plates that is capable of producing these large events.

The Earth’s tectonic plates are always in motion and they move at a rate of millimeters to centimeters per year. Faults that are locked allow tectonic stress to build up over time and then release the stress suddenly and violently in an earthquake. Faults that have had a large rupture within the recent geologic past have not had enough time to build up large stresses, so the probability of having another large event is low. Faults that have not had a large event in the recent geologic past have accumulated tectonic stress and therefore have a higher probability of producing a large earthquake. This is the case with the San Andreas Fault, which is the fault most likely to produce a significant earthquake in California. The southern section of the fault has the highest probability of producing a large earthquake because that section of the fault has not produced a significant event in recent history.

References:

California Standards (2003). "Science Content Standards for California Public Schools Kindergarten Through Grade Twelve" <http://www.cde.ca.gov/be/st/ss/documents/sciencestnd.pdf> (July 6, 2011)

Bolt, Bruce A. (1993). "Earthquakes", W.H. Freeman and Company, New York.

de Boer, Jelle and Sanders, Donald Theodore (2005). "Earthquakes In Human History", Princeton University Press, New Jersey.

2007 Working Group on California Earthquake Probabilities (WGCEP 2007). "Uniform California Earthquake Rupture Forecast (UCERF)" <http://www.scec.org/ucerf/> (August 16, 2011)

Experiment_Results

Figure 4: Example table of experiment results

QCN_Recording

Figure 5: Example screen shot of QCN recording.

UCERF: Map of California Area Earthquake Probabilities

Figure_6

Figure 6. "The colors on this California map represent the UCERF probabilities of having a nearby earthquake rupture (within 3 or 4 miles) of magnitude 6.7 or larger in the next 30 years. As shown in the table, the chance of having such an event somewhere in California exceeds 99%. The 30-year probability of an even more powerful quake of magnitude 7.5 or larger is about 46%. (2007 Working Group on California Earthquake Probabilities (WGCEP 2007))"

UCERF: California Area Earthquake Probabilities, Northern vs. Southern

Figure_7

Figure 7. "The dashed line of this California map is the boundary between northern and southern California used in the UCERF study. As shown in the table, the 30-year probability of an earthquake of magnitude 7.5 or larger is higher in the southern half of the state (37%) than in the northern half (15%). The colors represent the same local probabilities shown in Figure 6. (2007 Working Group on California Earthquake Probabilities (WGCEP 2007))"


Learning modules in this series:

Assessment

Name:___________________________

Worksheet 1: Fault Slip

  • Before beginning each trial, let the QCN device return to ambient background noise. This can take up to 60 seconds. Slowly and steadily pull the cord back 1 centimeter.
  • Pull the cord another centimeter and pause. Keep pulling back the cord 1 centimeter at a time until the brick slips. On the computer, take a screenshot of the earthquake when it reaches the middle of the screen. That way the ongoing vibrations will also be in the picture. When you save the screenshot to the computer, give it a unique name for that experiment.
  • Write on the board the displacement distance in millimeters and the number of centimeters the brick was pulled back to cause the slip. The displacement is the distance the brick has moved in millimeters. Record the minimum and maximum acceleration of the x, y, and z axes (horizontals and vertical) from the QCN screen. The units of acceleration are cm/sec/sec. The amplitude of the acceleration pulse is the distance between the maximum and minimum accelerations. The screen automatically adjusts the vertical scale so the max and min can be read off the screen with more accuracy. See Figure 4 as an example.
  1. As tension is slowly increased on the cord do you think the brick will slip at equal time intervals? Explain.
  2. Before beginning each trial, let the QCN device return to ambient background noise. This can take up to 60 seconds. Slowly and steadily pull the cord back 1cm.
  3. Pull the cord another centimeter and pause. Keep pulling back the cord 1 centimeter at a time until the brick slips. On the computer, take a screenshot of the earthquake (Figure 5). Fill in the blanks in Table 1. The displacement is the distance the brick has moved in millimeters. The x, y, and z axis acceleration amplitudes are read off the QCN screen. The screen automatically adjusts the vertical scale so the max and min can be read off the screen with more accuracy. See Figure 4 for an example.
  4. Reset the brick to the beginning of the board and repeat Step 3 for a total of 10 times.
  5. Find the max amplitude values of acceleration on the x, y, and z axis. The maximum acceleration is the greater of the absolute value of the minimum and the maximum accelerations.
  6. In Excel, graph the fault displacement to the number of centimeters the cord was stretched on each slip. What do you see?
  7. What trends do you see from the data? How is the fault displacement related to the acceleration amplitudes the QCN device measured?
  8. Compare your data to another group’s if there are multiple groups and write down what you see. How does their data compare to yours?
  9. Now that you have run the experiment, if you were to run it again do you think the slip would be the same?
  10. What are some possible experimental errors in this experiment?
  11. What are some ways to minimize the experimental errors that you just listed?
  12. What are some unavoidable experimental errors?


Worksheet 2: Earthquake Magnitude!

In this exercise you will calculate the Energy Magnitude of the earthquake generated. There are multiple equations to calculate magnitude. You are probably most familiar with the Moment Magnitude Scale. This is commonly referred to as the Richter scale. All magnitude scales are logarithmic scales. Go through steps 1-4 for all of the slip events recorded in Worksheet 1. There is an example for every step as well as a completed example (Figure 4). Fill in Table 1 using your findings from Worksheet 1 and the following steps.

  1. Find the pulling force required to move the brick.

Fp=m*g

Fp=Pulling Force, or the force required to move the brick.

m=Mass of the brick.

g=The acceleration due to gravity = 9.8m/s2.

1kg m/s2 equals 1 Newton (N)

1kg m/s2=1N

Fp=1.1kg*9.8m/s2

Fp=10.78 kg m/s2

Fp=10.78N

Compute the energy released from the earthquake for all of the experiments and record in Table 1.

E=Fp*D

E=Energy

Fp=Pulling force. This was computed in the last step.

D=Displacement in meters. Don't use millimeters or the calculation will be thrown off.

1m=1000 mm

1Nm=1 Joule (J)

E=(10.78N)*0.056m

E=0.604Nm

E=0.604J

Calculate Energy Magnitude for all of the experiments and put it in Table 1.

ME=(log10E-4.8)/1.5

ME=Energy Magnitude

E=Energy of the Earthquake. (Calculated in previous step.)

The magnitude that you calculate will be a negative number.

ME=(log10(0.604)-4.8)/1.5

ME=(log10(-0.219)-4.8/1.5

ME=(-5.02)/1.5

ME=-3.35

  1. If you have been using a spreadsheet in Excel, arrange the data from largest displacement to smallest and compare this to the Energy Magnitude (ME).

Extensions

Scaling

Additional Experiments:

  1. Glue different grit sandpapers to boards and test slip displacement on different frictional surfaces. Have the students run a comparison of the slip displacements of the different papers. In Excel, arrange the data in ascending order of magnitude of displacement and graph the line. Compare the lines of the different frictional surfaces. What does this tell you? Does the fault slip more and release more energy with higher grit sandpaper or lower grit? Explain.
  2. Ask the students to design their own experiment using this equipment and the QCN sensor.

Cite this work

Researchers should cite this work as follows:

  • Sandra Seale; Joe Paul Trudeau; NEES EOT (2011), "Fault Slip - Grades 9-12," http://nees.org/resources/3920.

    BibTex | EndNote

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