The S Wave Shadow Zone

• The S wave shadow zone is an area on the Earth’s surface where no S waves from a particular earthquake are detected.
• S waves, also known as secondary waves, are a type of seismic wave and they cannot travel through the liquid outer core of the Earth.
• When an earthquake occurs, the released energy travels in all directions in the form of seismic waves.
• These waves travel outwards from the earthquake’s focus, and scientists use them to study the structure of the Earth.
• As S waves approach the Earth’s liquid outer core, they are absorbed, creating an absence of these waves beyond a certain angle from the earthquake. This forms the S wave shadow zone.
• The S wave shadow zone is a crucial piece of evidence for the existence of a liquid outer core. It begins at an angle of approximately 105 degrees from the earthquake’s epicentre and extends around the planet on the side opposite the earthquake.
• The exact size and shape of the S wave shadow zone can vary from one earthquake to another, depending on factors such as the earthquake’s depth and the Earth’s physical properties.
• The discovery of the S wave shadow zone was a significant advancement in our understanding of the Earth’s structure and composition.
• The information obtained from studying S wave shadow zones can help in predicting future seismic activities, and contribute to seismic hazard evaluation, towards reducing disaster risk.

When revising the concept of the S wave shadow zone, it is beneficial to use diagrams illustrating the propagation of seismic waves and the formation of the shadow zone. You can also use these diagrams to illustrate the difference between P waves and S waves, and how each type of wave interacts with the Earth’s interior.