Seismic Waves

When an earthquake occurs, ground vibrations are generated that travel as waves throughout the Earth. Just as sound waves travel in the air, allowing us to hear, seismic waves travel outward from an earthquake through the materials of the earth. The following 6 frames show the progression of the primary (P) waves and the surface waves as they expand outward from the 1994 Northridge, California, earthquake.

The P waves are shown in red on the global view to the left and the cross-sectional view on the right. The much slower surface waves are shown in blue on the left and yellow on the right.

These frames were captured from the program Seismic Waves written by Alan Jones. This PC-based program shows an animation of the various waves, including the secondary (S) waves, as they expand outward from an earthquake's source.

15 seconds after earthquake.

45 seconds after earthquake.

1 minute after earthquake.

2 minutes after earthquake.

3 minutes after earthquake.

4 minutes after earthquake.