Seismic Waves Through the Earth.ppt

Evidence of Internal Structure

  • Granite

    • Density: 5.8 g/cm³ compared to crust density of 2.8 g/cm³

    • Allows speculation on probable compositions

  • Basalt

  • Meteorites

    • Utilized to determine Earth's composition and age

  • Seismic Waves

    • Travel times and direction provide insights into Earth's internal structure

Types of Seismic Waves

  • S Waves

  • P Waves

    • Primary Waves

      • Push and pull movement

      • Travel fastest (~ 6 km/sec)

      • Can travel through solids and liquids

    • Secondary Waves

      • Move side-to-side

      • Slower (~ 4 km/sec)

      • Can only travel through solids

Seismic Waves Through Earth

  • P-wave and S-wave records at seismic stations identify different internal structures

  • Epicenter Location

    • Displays zones of P-wave and S-wave recordings

    • Key observations include:

      • Seismic Station records both P and S waves

      • Seismic Station records no P or S waves (indicating the S-wave shadow zone)

      • Seismic Station records P waves only

  • Various angles (105°, 140°) imply different characteristics of seismic wave propagation through Earth's layers.