Types of Seismic Waves
Primary Waves (P-waves):
P-waves move the most rapidly out (7-8 km/sec) of the three. P-waves arrive at a given location before the other types. They travel deep within the Earth's interior, and moves through both solids and liquids (through the whole Earth). P-waves move straight, and expand and contract on the way. They are least damaging of all the waves. Secondary Waves (S-waves): The second fastest (4-5 km/sec), arriving at a give location after the P-waves. S-waves travel deep within Earth's interior also, but they only travel through solids (crust and mantle). S- waves travel up and down, in a S-like motion, and they are more destructive then P-waves. Long Waves/Surface Waves (L-waves/R-waves): L-waves/R-waves are also called surface waves, and they are the slowest of the three (3 km/sec). L- waves travel along and just beneath Earth's surface, and only through solids (crust and mantle). L-waves/R-waves move all around, and they are the most destructive. |
Using Seismic Waves to Learn About Earth's Interior
The behavior of seismic waves allow scientists to make inferences about Earth's interior. As seismic waves pass through the Earth, they slow down or speed up depending on the density and state of the materials they pass through. Seismographs can record the waves produced by strong earthquakes on the other side of the world. Scientists study these waves, and they are able to map boundaries between the four main layers of Earth's interior: the solid, core, the liquid outer core, the semi-solid mantle, and the solid crust. Also, sometimes dynamite is put below the ground to help determine the Earth's interior.
What Seismic Waves Tell Scientists About Earthquakes
Scientists can use the direction and the difference in the arrival times of P-waves and S-waves to determine the distance to the source of the earthquake.