Ground Motion - 3

A Combination of Waves

Real ground motion during an earthquake is made up of many waves of different amplitudes and frequencies. (Explain). The main shaking of the ground that is felt has frequencies up to 20 Hertz.

This graph shows how the position of a patch of ground changed with time during a real earthquake, the 1989 Kalamata earthquake in Greece. The motion does not have the simple form of a single wave with constant frequency and amplitude. Instead it looks much more complicated. (Animate)


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Vibrating Buildings
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from Bristol University