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