Earthquakes IV: ERT, Waves

Waves

  • wavelength: distance over which the wave repeats
  • amplitude: distance from undisturbed position to point of max displacement (crest or trough)
  • frequency: number of waves that pass a given point in a certain amount of time
    • higher frequency waves attenuate more quickly than lower frequency waves

Seismic Waves

  • in an earthquake, energy is released when movement begins at the hypocenter
  • the energy moves outwards as seismic waves through the earth
    • like sound waves in a rock
  • body waves: travel through the (body of) earth
    • p-waves
    • s-waves
  • surface waves: travel near surface only
    • love waves
    • Rayleigh waves

Body Waves

  • travel through (body of) earth
  • faster than surface waves
  • generally not damaging to buildings
  • can travel across/around the earth
  • 2 types: p and s waves

P-Waves

  • p = primary (or pressure)
  • fastest, they arrive first\
  • wave motion: parallel to direction of wave propagation

S-Waves

  • s = secondary (or shear)
  • slower than P-waves, but still much faster than surface waves
  • wave motion: perpendicular to direction of wave propagation

Surface Waves

  • travel near the surface only
  • slower than body waves
  • carry energy for greater distances away from the epicenter
  • very damaging to buildings
  • 2 types: love an Rayleigh waves

Love Waves

  • first described by british mathematician A.E.H Love
  • much slower than body waves
  • move side to side, perpendicular to direction of wave propagation

Rayleigh Waves

  • predicted to exist by Lord Rayleigh
  • much slower than body waves
  • move backwards- rotating, elliptical motion

\
\