shadow zone

The term "shadow zone" in physics typically refers to areas where seismic waves from an earthquake cannot be detected. This phenomenon provides crucial information about the Earth's interior.

When an earthquake occurs, it generates seismic waves, primarily P-waves (primary, compressional) and S-waves (secondary, shear). P-waves travel through solids and liquids, while S-waves can only travel through solids. Due to their different speeds and how they interact with different materials, P-waves and S-waves create distinct "shadow zones" on the opposite side of the Earth from the earthquake's epicenter.12

The existence and size of these shadow zones help scientists understand the Earth's structure, particularly the liquid outer core, which prevents S-waves from passing through it, creating a larger S-wave shadow zone than the P-wave shadow zone.2