How do seismic waves move?
A rock dropped into calm water makes waves traveling outward in all directions through the water. A popped balloon sends sound waves outward in all directions through the air. The same thing happens during an earthquake. Rocks deep inside the earth suddenly move sending seismic waves outward in all directions through the earth. Three types of seismic waves are created by earthquakes. • Primary (P) waves are pressure waves caused when rock is pushed or pulled forward or backward. Primary waves, the fastest wave sent out by an earthquake, travel down into the earth through both solids and liquids. (Remember: P waves – primary (first to arrive), pressure, push-and-pull). • Secondary (S) waves are shear waves caused when rock is shaken or whipped from side-to-side, like the wavy motion of a slithery snake. Secondary waves, the second-fastest wave sent out by an earthquake, travel down into the earth through solids (not liquids) only. (Remember: S waves – secondary (second to arrive), shear
