Geocentric Science

Seismic waves are also known as earthquake waves. Once rock reaches its elastic limit, and the rock snaps back and forth releasing the built-up stress, energy is released. The energy (or vibrations) are transmitted through the rock outwards in all directions.

1. What are the different seismic waves?

   Answer: There are surface waves (transport energy along the Earth’s surface), and body waves (transport energy through the body of Earth). There are two types of body waves, transverse waves and longitudinal waves.

2. What are P-waves?

   Answer: P-waves are also known as longitudinal waves, and alternate between compression and expansion in the same direction that the wave is traveling. P-waves are also known as primary waves because they are the first waves to reach a seismograph after an earthquake. P-waves travel faster than the other seismic waves and can travel through solids, liquids, and gases (all three states of matter can be compressed and expanded). The velocity of P-waves will increase as it moves through denser material.

   Image from Wikipedia

3. What are S-waves?

   Answer: S-waves are also known as transverse waves or shear waves, and twist the rock back and forth. S-waves deform rock and travel perpendicular to the direction of travel. S-waves arrive second (they are secondary waves) to a seismograph station. S-waves can only travel through solids.

   Images from Wikipedia

4. What are the types of body and surface waves?

   Answer: There are two types of body waves, P-waves and S-waves. Additionally, there are two types of surface waves, Love waves (L-waves), and Rayleigh waves. The surface waves do the most damage to the structures on the Earth’s surface.

5. Why are P-waves and S-waves important?

   Answer:

   A. Seismic waves provide information about the Earth’s interior. After an earthquake, P-waves can be detected almost at all seismographs around the world. However, this is not the case for S-waves; S-waves disappear completely. (The zones in where seismic waves cannot be detected is known as a shadow zone). Is information was used to prove that the Earth must consist of different states of matter (solids, liquids, and gases). Since P-waves are detected throughout the world, they can travel through all states of matter. S-waves disappear, and therefore can only travel through solids.

   Image from Wikipedia

   B. P-wave and S-wave information can be used to help scientists determine the distance to the epicenter of an earthquake.

   C. Scientists can use seismic wave information to look at earthquake trends and patterns and in order to detect danger zones.