Exploring Seismic Waves
Name_____________________________________ Date____________
Section: _______________________________ Group: _______________
The teacher will demonstrate seismic waves using a slinky. The teacher will
have three students help as volunteers. One student will be timing the waves on the
Slinky (one complete trip, back and forth). The other two students will be hold the slinky
at each end.
P-WAVES (PUSH –PULL):
1.
The students will start by pulling the Slinky toward themselves a bit and then
pushing it away. Draw your observations below:
2.
The volunteer students will do 3 trials of the P-wave, timing the wave as it
does one complete trip back and forth. Record the information below:
Trial 1:
3.
Trial 2:
Trial 3:
Take the average (find the mean) of the 3 trial times.
You should see that the vibrating parts of the Slinky move back and forth along the
same direction in which the wave is traveling. This type of wave is called a
longitudinal wave or a compression wave, and it is a model for seismic primary
waves, or p-waves. They’re known as primary waves because they are the fastest of
the earthquake waves, arriving first at distant points.
S-WAVES (SIDE TO SIDE):
1.
The volunteer students will shake one end of the Slinky from side to side.
Record your observations below:
2.
The volunteer students will do 3 trials of the S-wave, timing the waves as it
dos one complete trip back and forth. Record the information below:
Trial 1:
3.
Trial 2:
Trial 3:
Take the average (find the mean) of the 3 trial times.
This time you should see a type of wave is called a transverse wave. A transverse wave
can move through the bulk of a solid although it cannot move through liquid or gas. The
transverse wave you made with the Slinky proves a model for seismic waves called
secondary waves, or s-waves that travel through solid rock. There are really 2 types of S
waves. S-H (S-Horizontal) waves (which you just demonstrated) and S-V waves (SVertical) which you could demonstrate by moving the Slinky up and then down and
watching the wave.
SO WHAT IS GOING ON???
When an earthquake begins the stress on large blocks of rock becomes greater than the
strength of the rock. The rock breaks, releasing large amounts of energy. This energy is
carried outward in all directions by various seismic waves, some of which can reach the
opposite side of the earth in about twenty minutes. The further the waves travel from the
focus of the earthquake, the weaker they become.
P-waves push and pull the underground rocks, causing structures on the surface to move
back and forth. SH-waves move the rocks beneath the earth's surface from side to side,
giving buildings on the surface a good shaking, often with very damaging effects. With
SV-waves, the shaking is in a vertical direction-which sometimes can be enough to
launch you out of your seat. S-waves and P-waves cause high-frequency vibrations that
tend to cause low buildings to vibrate more than tall structures.
Surface waves are long, slow waves. The low-frequency vibrations that they induce in
buildings have more effect on tall buildings than on low ones. Love waves shake things
from side to side. The slowest seismic waves, Rayleigh waves, are rolling waves that
make you feel as if you're struggling to keep your balance on a ship in the open ocean.
Analyze and Conclude
1)
What are seismic waves and describe two types.
2) Why do we study seismic waves?
Why study seismic waves?
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2. 2. Why study seismic waves?
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4) Identify each diagram as either P-wave or3. ____ S-wave:
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3. ____ 4. ____ 3. ____ 4. ____ s. . ___________________
4. ____ Compressions
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Compressions
5. ____ 6. ____ Undisturbed medium
Compressions
5. ____ 5. ____ Dilatations
6. ____ 6. ____ Undisturbed medium
Dilatations
Undisturbed medium
Dilatations
7. ____ 8. ____ 6. ____ 9. ____ and ____ are surface waves. 7. ____ 8. ____ 7. ____ 8. ____ ___________________
___________________
11. ____ is the fastest surface wave. 9. ____ and ____ are surface waves. 10. ____ and ____ are body waves. 9. ____ and ____ are surface waves. 10. ____ and ____ are body waves. 13. ____ and ____ are used to determine the 8. ____ epicenter of an earthquake. 11. ____ is the fastest surface wave. 12. ____ is the fastest body wave. 5) In your own words, describe how seismic
waves travel through the Earth.
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Seismic Waves
Seismic Waves