Analyzing Seismic Waves (Denise Randol)

Analyzing Seismic Waves: Animations & Modeling

Principle(s) Investigated:

• Energy generated by a seismic event travel by vibrating particles of matter.
• differences in wave movement and effects,
• Seismic waves travel outward from the focus in all directions, similar to a rock dropped in a pool of water
• Seismic waves differ in speed and type of movement
• Effect of seismic waves on man-made structures is dependent on type of wave movement.

Explanation:

Waves are a disturbance in matter that transports energy. The matter that is moved by the wave does not move with the wave. The matter usually moves in a small motions called 'particle motion' and continues to move until the wave energy has passed through the matter. After the wave has passed, the matter will generally return to its original condition. However, if the event is strong enough, such as an earthquake, the matter (land or buildings) can be possibly permanently deformed.

These activities provide introductory wave concepts for students. In the activities, they will use a variety of models to simulate the movement, properties and effects of seismic waves.

• In Seismic Wave Animation, students analyze the 3 main seismic waves: P-wave (primary or pressure), S-wave (secondary or shear), and surface wave (Rayleigh or Love).

• In Slinky Wave Model, students use slinks to demonstrate understanding of different wave movement and observe changes in wave speed. In Kinesthetic Model, students work in groups to act out how seismic energy travels through matter (their bodies).
  • These models can be used as a Formative Assessment of student conceptual understanding following the reading and animation activities.
• In Water Tank Wave Model, students observe the movement of multiple waves, outward in all directions, and the differences in movement of floating boats.

Standards:

NGSS: Earth's Systems

• MS-ESS2-2 Construct an explanation based on evidence for how geoscience processes have changed Earth's surface at varying time and spatial scales

Physical Science

• MS-PS4-2 Develop and use a model to describe that waves are reflected, absorbed, or transmitted through various materials.

Common Core Objectives:

English

• Students engage effectively in collaborative discussions with diverse partners and in different groupings on sixth-grade topics and texts.
• Developing academic as well as domain-specific vocabulary
• Students use technology to find resources and gather information

Materials:

For Teacher Demo (Wave Tank & Wave Animation as whole class)

• Student demo handouts (one per) Wave Animation I and II handout currently being re-formatted will add soon as shared doc
• see thru wave tank with grid (such as a long aquarium or plexiglas demo tank
• IRIS wave animations
• AmaSeis Software (seismogram demo)

Figure 1

Figure 1. This is a large wave tank using a plastic storage container (75 liter "under bed" container) appropriate for whole class demo. Container is positioned on table top. Other shallow containers such as long glass Pyrex baking pans can be used for student groups or with an overhead projector of Document Reader.

Distances in cm are marked on the bottom of the container for convenient measurement of wave velocity from the distance and travel time. (Grids can be marked ahead of time with a waterproof marker such as a Sharpie).

Small floating flags are used for identifying the time and relative amplitude of propagating water waves.

Figure 1 shows time lapse A- ball just above water, B- impact with water, C- wave propagation to first boat, D- wave

For Student Groups

Smaller Wave Tank model

• shallow pan, under bed storage container, or stream table
• styrofoam blocks (2 X 2 x 1 cm) 4 per group
• ping pong balls- one per group
• Toothpicks 4 per group
• Scotch tape
• Colored Paper for flags
• thread with a coin or washer anchor taped to end (see figure 2)
• Scissors
• Video Physics ap installed on smart phone

Figure 2 The flags are made from small floats (about 2x2x1 cm rectangular blocks of closed cell foam, Styrofoam or cork) with a toothpick and piece of tape attached. The floating flags are very sensitive to wave motion in the wave tank.

For Slinky Wave Model

• Slinky: one per pair of students- 16 for class of 32, etc
• Gum Drop candy such as Dots- 1 per slinky

For Wave Animation Activity

• All students access to computer viewing of Wave Animations video (either projected by teacher's computer & projector -whole class OR shared or individual lap top/tablets.
• Go to this link for Wave Animations, scroll down to appropriate wave diagram and click on image to activate animation http://web.ics.purdue.edu/~braile/edumod/waves/WaveDemo.htm Site gives option to download individual animations onto your computer without the accompanying text
• Wave Animation I and II handout
• Pencil for recording responses and creating wave diagrams

Procedure: Lesson can be divided into 3 class periods or compressed into 2

Part I Seismic Wave Animation Model (50 min)

1. Show class video clips at top of page: "World Record Wave" and "Ocean Waves"
2. Students respond to questions in Quickwrite
   • What did the two videos have in common?
   • What other kinds of waves can you think of?
   • Why are earthquakes called 'seismic waves'
3. Students read What are Seismic Waves
   1. Students view http://web.ics.purdue.edu/~braile/edumod/waves/WaveDemo.htm (animation videos of 4 kinds of waves
   2. Complete Wave Animation Handout while viewing videos

Part II

Slinky Model

1. Pair students and distribute Slinkies. (Caution students about excessive pulling of Slinky will permanently deform it)
2. Students use desk tops or open space such as a hallway to experiment with recreating P and S waves
3. Ask students to determine which wave (P or S) appear faster.
4. Distribute a candy gum drop to Slinky group. Students attach gum drop to center coil of Slinky to represent structure on surface.
5. Use smart phone Ap to record movement of energy through Slinky.
1. Upload videos to class Drop Box.

Kinesthetic Model

1. Form student groups of approx. six. Students line up side by side and model P wave (chain reaction shoulder bump) and S wave (chain reaction bend forward at waist--like taking a bow) Love wave can be shown by going extending arms forward palms out and then rotating hands in a circular manner.

Part III Water Tank Wave Model (30 min)

1. Teacher can demonstrate small wave tank with overhead projector/document camera or use larger container for students to observe standing around tank
2. Student wave tanks: Prep containers with grid marked

Student Prior Knowledge:

• Students know the Earth can move suddenly and powerfully.
• Students have viewed video clips of real time earthquakes as they happen and images of earthquake effects.
• Students have recorded impressions/observations.

Questions & Answers:

Q: Based on the movement of each kind of wave, describe the impact these waves have on three structures: a bridge, a tall building and a one-story home.

A: P wave might cause initial jolt, a shudder that travels through structure but then returns to origin, S wave might cause back and forth shaking that may knock loose items to ground, Surface waves would cause the most damage. The waves would push and pull the structures in circular and back and forth movements. The structure can become separated under the stress of the wave movement.

Q: In what ways can you design a structure that is more resistant to the effects of surface waves?

A:Adding support beams that are positioned in a triangular way between walls, supporting walls that are steel reinforced, shock obsorbers in basement to allow movement.

Q: In what ways did the Slinky model not show the correct comparative speeds of P and S waves? Why did the S wave appear faster?

A: The friction of the floor is greater when the Slinky coils are pushed forward and less when the Slinky coils move side to side. (See "Seismic Slinky: Analogy for P & S Waves" Youtube link below.

Applications to Everyday Life:

Movement of waves through structures is examined in the auto industry when designers try to make cars more impact resistant. They use modeling to watch the direction of waves and stressors on the car's body and frame.

Videos:

http://www.iris.edu/hq/programs/education_and_outreach/videos

Extensive collection of short lecture videos: Epicenter & Focus, Locating Epicenter, Seismic Wave Paths, Elastic Rebound, Building Strength Demo and Seismic Slinky (listed separately below)

Seismic Slinky: Analogy for P & S Waves

This video is a middle school teacher demonstrating slinky waves and asking terrific questions about why model is a good and flawed model for P and S waves.

Websites to animations, demos and software

http://web.ics.purdue.edu/~braile/new/SeismicWaves.ppt Informative powerpoint to give teachers background info

http://web.ics.purdue.edu/~braile/new/SeisVolE2010CSTA.ppt

http://web.ics.purdue.edu/~braile/new/SIS.ppt

References:

Primary source for many parts of this lesson, includes photos, resources and pictures from L. Braile, Purdue University.

http://web.ics.purdue.edu/~braile/edumod/slinky/slinky4.htm

http://web.ics.purdue.edu/~braile/edumod/slinky/slinky.htm

Lesson 6: Earthquake Waves. Additional suggestions on Slinky and rope wave models and management of students during activity. http://www.nature.com/scitable/topicpage/lesson-6-seismic-waves-8678528

Wampler, J. M. Misconceptions: A column about errors in geoscience textbooks.Journal of Geoscience Education 50, 620–623 (2002).

Photographs: Include a photograph of you or students performing the experiment/demonstration, and a close-up, easy to interpret photograph of the activity --these can be included later.