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When we listen to music we hear a wide range of sound frequencies
or notes. When we feel an earthquake we feel a wide range
of frequencies but unlike music the notes are less distinct.
People describing what they felt during an earthquake may
call it a "sharp jolt" or a "rolling motion." The sharp jolt
is due to high frequencies while the rolling motion is due
to low frequencies. What you feel during an earthquake is
a product of the earthquake itself, how far you are from the
earthquake, and the types of rocks between you and the earthquake.
To learn about this we will convert the shaking during earthquakes
to sound and then listen to the sounds.
Converting Shaking to Sound
When a loudspeaker produces sound it shakes. During an earthquake
the ground shakes. To convert the earthquake shaking to sound
we make the loudspeaker shake the same way the ground did. But,
if we really did that the sound would be too low for people
to hear. So, we speed things up so that the loudspeaker moves
back and forth much faster than the ground did and then we can
hear it.
Tips for listening
The sound files on these pages are in .wav format. If your browser
can't play them back, you will need to install
a plugin that will do this.
The sounds on these pages require a good loudspeaker. If
your computer doesn't have good speakers (a subwoofer is best)
then try using a pair of headphones. Even the headphones that
come with many personal tape player or "Walkmans" will work.
Created by Andy Michael, USGS, and Daniel Ross, 12 year old
USGS Volunteer for Science. |
