Seismic Waves

Seismic Waves

Seismic waves come in several types as shown below:

P-Waves

Primary (they arrive first), Pressure, or Push-Pull.

Material expands and contracts in volume and particles move back and forth in the path of the wave. 
P-waves are essentially sound waves and travel through solids, liquids or gases.Ships at sea off the California coast in 1906 felt the earthquake when the P-wave traveled through the water and struck the ship (generally the crews thought they had struck a sandbar).

S-Waves

Secondary (arrive later), Shear, or Side-to-side. 

Material does not change volume but shears out of shape and snaps back.Particle motion is at right angles to the path of the wave.Since the material has to be able to "remember" its shape, S-waves travel only through solids.


Surface Waves

Several types, travel along the earth's surface or on layer boundaries in the earth.

The slowest waves but the ones that do the damage in large earthquakes.