# Seismic Waves Question 1, 2, 3

Describe seismic waves.

By

Zach Beam, Amanda Towry, Jim Stith

What are the types of seismic waves? How are they different from one another?

P Waves are compression waves (longitudinal waves) These waves are faster than S waves

S waves are transverse waves (perpendicular to the direction of the wave) Arrive at the seismometer after primary waves

Surface waves:

Love waves move back and forth (side to side)

Rayleigh waves move in an elliptical path

Further resources:

http://eqseis.geosc.psu.edu/~cammon/HTML/Classes/IntroQuakes/Notes/waves_and_interior.html

How do the various types of seismic waves propagate through the earth?

"In style" (Towry, 2016)

Refraction-based on density.  This changes as the waves go through different materials.  The Angle of Incidence and Angle of Refraction causes P and S waves to curve.There is a shadow zone where body waves are not detected due to refraction.

Reflection-the wave doesn't just refract, but it also reflects at the junction of the rocks.  Then you have two waves propagating through the Earth.

Dispersion-Only applicable to the surface waves.  Different periods travel at different velocities so the effects of dispersion become more apparent over distances. Cliff notes: Stronger waves travel further.

Further resources:

http://eqseis.geosc.psu.edu/~cammon/HTML/Classes/IntroQuakes/Notes/waves_and_interior.html

Why are seismic waves important to LIGO?

Because LIGO measures the "squishy and expansiony thingy" (Beam, 2016) of gravitational waves.  In order to eliminate the background noise of seismic activity, LIGO must know what is going on in the ground in order to rule it out.