Seismic Shadow Zones: S wave shadow zone

How do S waves give evidence for a liquid outer core?

A seismic shadow zone is an area of the Earth's surface where seismographs cannot detect an earthquake after its seismic waves have passed through the Earth. This animation addresses 3 common variations of S-type seismic body waves. All are shear waves that travel in all directions away from the epicenter of an earthquake. The different phases show how the initial S wave is stopped, or changes when encountering boundaries in the Earth.

There are 3 common variations of S-type seismic body waves. All are shear waves that travel in all directions away from the epicenter of an earthquake. The different phases show how the initial S wave is stopped (damped), or how it changes when encountering boundaries in the Earth.


Keypoints:

  • Seismic shadows are a global effect of seismic waves from large earthquakes
  • S waves radiate spherically away from an earthquake in all directions
  • S waves don’t appear beyond an angular distance of ~103°
  • S waves are stopped by the liquid outer core


Level: Novice

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