How do seismic waves travel through the Earth?
Video lecture describing speeds and paths of different seismic waves within Earth from an earthquake to a distant seismic station. P & S waves travel through the Earth; Surface waves travel around the perimeter of the Earth.
P Waves: Compressional waves that travel through the Earth. Fastest waves. S Waves: Shear waves travel through the solid part of the Earth. Slower than P waves. Surface Waves: Love & Rayleigh waves travel along the surface of the Earth and are the last to reach distant seismic stations.
Seismic shadow zones have taught us much about the inside of the earth. This shows how P waves travel through solids and liquids, but S waves are stopped by the liquid outer core.
The wave properties of light are used as an analogy to help us understand seismic-wave behavior.
The shadow zone is the area of the earth from angular distances of 104 to 140 degrees from a given earthquake that does not receive any direct P waves. The different phases show how the initial P wave changes when encountering boundaries in the Earth.
The Earth has 3 main layers based on chemical composition: crust, mantle, and core. Other layers are defined by physical characteristics due to pressure and temperature changes. This animation tells how the layers were discovered, what the layers are, and a bit about how the crust differs from the tectonic (lithospheric) plates, a distinction confused by many.
Video lecture on wave propagation and speeds of three fundamental kinds of seismic waves.
Roll over the buttons to see the difference between P- and S-wave seismic paths as well as their respective shadow zones.
Seismic Waves is a browser-based tool to visualize the propagation of seismic waves from historic earthquakes through Earth’s interior and around its surface. Easy-to-use controls speed-up, slow-down, or reverse the wave propagation. By carefully examining these seismic wave fronts and their propagation, the Seismic Waves tool illustrates how earthquakes can provide evidence that allows us to infer Earth’s interior structure.
