How do waves waves travel through Earth and why seismic waves arrive at more distant places at higher speeds?

Question

Thanks you so much! Please state your source. :)

Answer 1

I've added a comment or two but most of this first part comes straight from this site:
http://www.geo.mtu.edu/upseis/waves.html...

(Wikipedia also has a good summary: http://en.wikipedia.org/wiki/seismic_wav...

There are several different kinds of seismic waves, and they all move in different ways. The two main types of waves are body waves and surface waves. Body waves can travel through the earth's inner layers, but surface waves can only move along the surface of the planet like ripples on water. Earthquakes radiate seismic energy as both body and surface waves.

The first kind of body wave is the P wave or primary wave (or pressure/compressional wave). This is the fastest kind of seismic wave. The P wave can move through solid rock and fluids, like water or the liquid layers of the earth. It pushes and pulls the rock it moves through just like sound waves push and pull the air. Have you ever heard a big clap of thunder and heard the windows rattle at the same time? The windows rattle because the sound waves were pushing and pulling on the window glass much like P waves push and pull on rock.

The second type of body wave is the S wave or secondary wave,(also called a shear wave) which is the second wave you feel in an earthquake. An S wave is slower than a P wave and can only move through solid rock, since liquids can't transmit the shearing motion. This wave moves rock up and down, or side-to-side.

Surface Waves
The first kind of surface wave is called a Love wave. It's the fastest surface wave and moves the ground from side-to-side.

The other kind of surface wave is the Rayleigh wave. A Rayleigh wave rolls along the ground just like a wave rolls across a lake or an ocean. Because it rolls, it moves the ground up and down, and side-to-side in the same direction that the wave is moving. Most of the shaking felt from an earthquake is due to the Rayleigh wave, which can be much larger than the other waves.



Now for speed:

The speed of a seismic (or acoustic, or sound) wave depends upon the material it is moving through. The denser the material is, the faster the acoustic waves move. Typical velocities for a P wave would be about 5000 meters/sec in granite (16,400 ft/sec), 1450 m/sec in water (4750ft/sec) and 330 m/sec in air (1080 ft/sec). So basically, the only way a seimic wave can arrive at a more distant place at a higher speed is if it was traveling through a more dense material.

Answer 2

P- waves(Primary) Are able to travel through liquids, gasses and solids therefore they get to the epicenter first!

S- Waves(shear OR Secondary) Travel only throught solids so they get there slower and definetly after the P-Waves! Also is you can imagine a slinky spread out and moving it up and down! Hope this helps!!!