Slinky seismology
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Slinky seismology is based on the tenet that almost anything to do with earthquake seismology can be demonstrated with one or more slinkys.
This type of demonstration is best done before a crowd, where one can bring up many volunteers. There is quite a controversy among "slinkyologists" as to the best type of slinky to use. Some prefer the antique all-steel versions (and are quite proud of being "retro"). Others prefer the genuine Slinky-brand fluorescent plastic slinkys, which are much longer and have better response than the generic types.
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[edit] Teaching Methodologies
[edit] Seismic Waves
As in the figure, start with a stretched slinky. Request a volunteer from the audience to be an endpoint. Stretch the slinky so it only has a slight sag.
The first seismic wave to demonstrate is a compression wave, or P-wave. These are best generated by gathering a few coils of the slinky and quickly releasing them. The wave moves very rapidly along the slinky and reflects back once it reaches the end. The volunteer acts as a wave detector, or seismometer, and as such should signal when the wave reaches them.
Shear waves (S-waves) can be generated by lifting a coil (slightly away from the hand), and releasing it. The audience will see that it travels more slowly to the seismometer (who must signal again).
At this point, it is possible to demonstrate the ability of seismometers to detect the amplitude of the wave hitting them. This can be done by amplifying the signal for a big wave and using a softer exclamation for a small wave.
[edit] Locating Earthquakes
This requires three slinkys and some more demonstrators. Set up two more human seismometers around a central human earthquake. Have one slinky go far away at full stretch, have another hold extra coils (for the medium distance). Finally, have them hold a lot of coils for the short distance.
Have the epicenter hold all three of the other ends. Now it becomes somewhat tricky. You have to calibrate the new seismometers with individual waves. Make sure they are giving a good yell at wave impact. The earthquake itself can gather coils and release them, although this often requires teaching assistance. With practice, this will lead to the experiment replicating the arrival of seismic waves at differing distances, including a rapid succession of yells.
This can be followed by a link into slides on real seismometers, and how computers locate the earthquakes (see Earthquake location).
[edit] Buildings
Although time consuming, a vertical slinky can demonstrate the fundamental modes of building response. It can also be used to demonstrate the effect of soft foundation soils. See response spectrum and seismic analysis for further information.
[edit] Giant slinky
The Heureka science exploratorium in Vantaa, Finland includes a giant slinky suspended by steel wire among its permanent exhibitions.
