Making Waves: Classroom Demos and Activities for Teaching About Seismic Waves Sheryl Braile, Happy Hollow School West Lafayette, IN Larry Braile, Purdue University braile@purdue.edu, www.eas.purdue.edu/~braile CSTA Convention, Oct. 2007, Long Beach, CA http://web.ics.purdue.edu/~braile/new/SeismicWaves.ppt Exploring Planet Earth

Seismic Waves Slinky – P, S, Rayleigh, Love waves; Reflection and transmission; energy carried by waves; elastic rebound/plate motions and the slinky; 5-slinky model – waves in all directions, travel times to different distances. Human wave demo – P and S waves in solids and liquids. Seismic wave animations – P, S, Rayleigh, Love waves; wave motion; wave propagation activity. Seismograms – Viewing seismograms on your computer (AmaSeis software). Seismic Waves software – Wave propagation through the Earth.

Why use several approaches to teaching about seismic waves?

Why use several approaches to teaching about seismic waves? Fundamental concept Different approaches for different settings or size of group Different learning styles Reinforce with more than one approach Demonstrations, animations and hands-on activities Use one or more approach for authentic assessment

Spring Extension (cm)* Elasticity – a property of materials that results In wave propagation and earthquakes Added Mass (g) Spring Extension (cm)* (adding masses) (removing masses) 0.0 0.3 100 3.7 3.6 200 7.7 7.5 300 11.4 400 15.3 15.1 * Difference in length of spring before and after adding mass.

Slinky and human wave demo and wave tank and elasticity experiments: http://web.ics.purdue.edu/~braile/edumod/slinky/slinky.htm http://web.ics.purdue.edu/~braile/edumod/slinky/slinky.doc http://web.ics.purdue.edu/~braile/edumod/slinky/slinky.pdf

Seismic P (compressional) and S (shear) wave propagation (both are body waves)

Seismic Rayleigh and Love wave propagation (both are surface waves)

Other Characteristics Characteristics of Seismic Waves Table 2:  Seismic Waves Type (and names) Particle Motion Typical Velocity Other Characteristics P,Compressional, Primary, Longitudinal Alternating compressions (“pushes”) and dilations (“pulls”) which are directed in the same direction as the wave is propagating (along the raypath); and therefore, perpendicular to the wavefront VP ~ 5 – 7 km/s in typical Earth’s crust;     >~ 8 km/s in Earth’s mantle and core;  1.5 km/s in water; 0.3 km/s in air P motion travels fastest in materials, so the P-wave is the first-arriving energy on a seismogram.  Generally smaller and higher frequency than the S and Surface-waves.  P waves in a liquid or gas are pressure waves, including sound waves. S,   Shear, Secondary, Transverse Alternating transverse motions (perpendicular to the direction of propagation, and the raypath); commonly polarized such that particle motion is in vertical or horizontal planes VS ~ 3 – 4 km/s in typical Earth’s crust;     >~ 4.5 km/s in Earth’s mantle;  ~  2.5-3.0 km/s in (solid) inner core S-waves do not travel through fluids, so do not exist in Earth’s outer core (inferred to be primarily liquid iron) or in air or water or molten rock (magma).  S waves travel slower than P waves in a solid and, therefore, arrive after the P wave.

Characteristics of Seismic Waves L,  Love, Surface waves, Long waves Transverse horizontal motion, perpendicular to the direction of propagation and generally parallel to the Earth’s surface VL ~  2.0 - 4.5 km/s in the Earth depending on frequency of the propagating wave Love waves exist because of the Earth’s surface.  They are largest at the surface and decrease in amplitude with depth.  Love waves are dispersive, that is, the wave velocity is dependent on frequency, with low frequencies normally propagating at higher velocity.  Depth of penetration of the Love waves is also dependent on frequency, with lower frequencies penetrating to greater depth. R,   Rayleigh, Surface waves, Long waves, Ground roll Motion is both in the direction of propagation and perpendicular (in a vertical plane), and  “phased” so that the motion is generally elliptical – either prograde or retrograde VR ~  2.0 - 4.5 km/s in the Earth depending on frequency of the propagating wave Rayleigh waves are also dispersive and the amplitudes generally decrease with depth in the Earth.  Appearance and particle motion are similar to water waves.

A simple wave tank experiment – a ping pong ball is dropped onto the surface of the water; small aid viewing of the waves; distance marks on the bottom of the container allow calculation of wave velocity.

Seismic P (compressional) and S (shear) wave propagation in the slinky

Seismic waves and the slinky (also, see the 4-page slinky write-up at: http://web.ics.purdue.edu/~braile/edumod/slinky/slinky4.doc and pick up your slinky and 4-page slinky handout at the IRIS booth, number 623) P and S waves Love and Rayleigh waves Wave reflection and transmission Elastic rebound Waves carry energy The five slinky model (waves in all directions and different travel times to different locations – the way that earthquakes are located)

Seismic waves carry energy Seismic waves carry energy. Observe the shaking of the model building when P and S waves are propagated along the slinky.

The 5-slinky model for demonstrating that seismic waves propagate in all directions and the variation of travel time with distance.

The human wave demonstration illustrating P and S wave propagation in solids and liquids.

Wave animations Animation courtesy of Dr. Dan Russell, Kettering University http://www.kettering.edu/~drussell/demos.html Seismic Wave animations (Developed by L. Braile) http://web.ics.purdue.edu/~braile/edumod/waves/WaveDemo.htm

Dan Russell animations – The people wave Animation courtesy of Dr. Dan Russell, Kettering University http://www.kettering.edu/~drussell/demos.html

Dan Russell animations – A wave pulse Animation courtesy of Dr. Dan Russell, Kettering University http://www.kettering.edu/~drussell/demos.html

Dan Russell animations – Transverse wave Animation courtesy of Dr. Dan Russell, Kettering University http://www.kettering.edu/~drussell/demos.html

Dan Russell animations – Rayleigh wave Animation courtesy of Dr. Dan Russell, Kettering University http://www.kettering.edu/~drussell/demos.html

Compressional Wave (P-Wave) Animation Deformation propagates. Particle motion consists of alternating compression and dilation. Particle motion is parallel to the direction of propagation (longitudinal). Material returns to its original shape after wave passes.

Shear Wave (S-Wave) Animation Deformation propagates. Particle motion consists of alternating transverse motion. Particle motion is perpendicular to the direction of propagation (transverse). Transverse particle motion shown here is vertical but can be in any direction. However, Earth’s layers tend to cause mostly vertical (SV; in the vertical plane) or horizontal (SH) shear motions. Material returns to its original shape after wave passes.

Rayleigh Wave (R-Wave) Animation Deformation propagates. Particle motion consists of elliptical motions (generally retrograde elliptical) in the vertical plane and parallel to the direction of propagation. Amplitude decreases with depth. Material returns to its original shape after wave passes.

Love Wave (L-Wave) Animation Deformation propagates. Particle motion consists of alternating transverse motions. Particle motion is horizontal and perpendicular to the direction of propagation (transverse). To aid in seeing that the particle motion is purely horizontal, focus on the Y axis (red line) as the wave propagates through it. Amplitude decreases with depth. Material returns to its original shape after wave passes.

Schematic diagram illustrating students performing wave simulations Schematic diagram illustrating students performing wave simulations. Student holds a poster board or cardboard circle in front of his or her body and walks forward (like the seismic waves propagating in the Earth). While walking, the student moves their circle forward and backward (“push and pull”, for the P wave), or up and down (transverse motion for the shear wave), or in a retrograde ellipse (for the Rayleigh wave), or side to side horizontally (for the Love wave), as shown above.

You can download the animations separately to run more efficiently (http://web.ics.purdue.edu/~braile/edumod/waves/WaveDemo.htm). A complete PowerPoint presentation on the Seismic wave animations is also available at: http://web.ics.purdue.edu/~braile/edumod/waves/WaveDemo.ppt

(developed by Alan Jones, SUNY Binghamton, NY) IRIS AmaSeis Software 24-Hour Screen Display Extracted Seismogram (developed by Alan Jones, SUNY Binghamton, NY)

Demonstrate the AmaSeis software for displaying and analyzing seismograms Software (Windows) available at: http://www.geol.binghamton.edu/faculty/jones/ A tutorial on AmaSeis and links to seismograms that can be downloaded and viewed in AmaSeis available at: http://web.ics.purdue.edu/~braile/edumod/as1lessons/UsingAmaSeis/UsingAmaSeis.htm

The Seismic Waves program (Windows) from Alan Jones, SUNY, Binghamton http://www.geol.binghamton.edu/faculty/jones/

IRIS Earth’s Interior Structure Poster – Seismic waves through the Earth

Earth’s interior structure and seismic raypaths that are used to determine the Earth structure.

Seismograms for waves traveling through the Earth.

Making Waves: Classroom Demos and Activities for Teaching About Seismic Waves Sheryl Braile, Happy Hollow School West Lafayette, IN Larry Braile, Purdue University braile@purdue.edu, www.eas.purdue.edu/~braile CSTA Convention, Oct. 2007, Long Beach, CA http://web.ics.purdue.edu/~braile/new/SeismicWaves.ppt Exploring Planet Earth