Seismic Shadow Zones vs Light Shadows

Can light shadows be compared to Earth's seismic shadow zones?

The wave properties of light are used as an analogy to help us understand seismic-wave behavior. Most shadows aren't black; that's because light reflects off of nearby objects and the redirected and reduced light energy strikes and brightens the area in shadow. Light can also bend, for example refracting at the water surface illuminating objects below the surface, or appearing to make half-submerged objects bend. Seismic waves also reflect and refract off layers in the Earth.


Properties of light give information about seismic shadow zones:

  • Shadows aren't devoid of light (seismic shadow zones aren't devoid of energy)
  • Light reflects and the redirected light, though reduced, brightens the area in shadow (P waves are redirected across boundaries yielding information about Earth's core)
  • Light can "bend", refracting across change in material (seismic waves refract at depth)


Total Time: 3min 16s
Level: Novice


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