Seismic Waves

Large-scale events (volcanoes, earthquakes, explosions) produce seismic waves that spread through the earth's layers.

Types of Seismic Waves

1. P Waves (Primary Waves)

   • Longitudinal waves.
   • Can travel through solids and liquids.
   • Much faster than S waves.

2. S Waves (Secondary Waves)

   • Transverse waves.
   • Can only travel through solids.

Importance of Seismic Waves

• Studying wave travel helps scientists understand the internal structure of the Earth.
• Seismologists use seismometers to detect waves.
• Comparing results globally helps determine travel times from earthquake sites, revealing clues about Earth's structure.

Wave Behavior at Boundaries

• Seismic waves can be:
  • Reflected
  • Absorbed
  • Transmitted

Refraction

• Waves change direction when passing through different mediums due to changes in speed caused by different densities.
• Sudden density changes lead to sudden changes in wave direction (e.g., between the mantle and liquid outer core).

Curved Paths of Seismic Waves

• Waves continuously refracted as they pass through different density mediums, appearing to curve.
• P waves can pass through the entire Earth, but S waves cannot travel through the liquid outer core, which was crucial for discovering its existence.

Detection of Waves

• P Waves are detected almost everywhere, while S Waves cannot be detected in regions between the outer core and other layers because of refraction.
• Understanding which waves are detected at various locations has been key to uncovering the Earth’s internal structure.

Conclusion

• The ability of P waves to travel through both solids and liquids and the restriction of S waves to only solids provided significant insights into Earth’s structure.

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