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Question
Explain the three types of earthquake waves.
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Solution
Three types of earthquake waves are:
- P-primary waves (P-waves):
- Nature: These are compressional waves that move in a back-and-forth motion along the direction of travel.
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Speed: They are the fastest seismic waves, travelling at speeds of 5-8 km/s.
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Movement: P-waves can travel through solids, liquids, and gases, which makes them the first to be recorded on a seismograph.
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Impact: Although they are the fastest, their movement causes only slight shaking compared to other waves.
- S-Secondary Waves (S-waves):
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Nature: These are shear waves that move in a side-to-side motion, perpendicular to the direction of travel.
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Speed: S-waves are slower than P-waves, travelling at speeds of 3-4 km/s.
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Movement: S-waves can only travel through solids and are unable to pass through liquids. They arrive after the P-waves and cause more intense shaking.
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Impact: S-waves are responsible for the major shaking during an earthquake and are more destructive than P-waves.
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- L-Long waves (or surface waves):
- Nature: These waves travel along the Earth's surface and are a combination of both P-waves and S-waves.
- Speed: Surface waves are slower than both P-waves and S-waves but cause more destructive shaking on the Earth's surface.
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Movement: They move in a rolling motion, similar to ocean waves, and can cause buildings to sway or even collapse.
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Impact: These waves are responsible for most of the damage during an earthquake because they produce the strongest ground movements at the surface.
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