How do s and p waves move through the earth? what happens to them as they move through the layers?

Answer 1

S and P waves are seismic waves that are generated during earthquakes and can also be generated by other sources such as explosions. These waves move through the Earth in different ways.

1. S waves (Secondary or Shear waves):
S waves are transverse waves, meaning that they cause particles to vibrate perpendicular to the wave's direction of travel. As S waves propagate through the Earth, they move in a shearing motion similar to waves moving through a rope. They are slower than P waves and cannot travel through liquids or gases, only through solid materials.

When S waves encounter different layers within the Earth, the following happens:
- In the Earth's outer core, which is a liquid layer, S waves cannot propagate and are completely absorbed. This is known as S-wave shadow zone.
- In the Earth's mantle, which is a solid layer, S waves can propagate, but they change direction and experience a decrease in velocity due to differences in density and composition.
- In the Earth's crust, S waves can propagate with minor changes depending on the specific properties of the crustal rocks.

2. P waves (Primary or Pressure waves):
P waves are compressional waves, meaning that they cause particles to vibrate parallel to the wave's direction of travel. These waves are faster than S waves and can travel through solids, liquids, and gases.

As P waves propagate through the Earth, the following happens:
- In the Earth's outer core, P waves can propagate but experience a slight change in velocity due to different density and composition compared to the mantle.
- In the Earth's mantle, P waves can propagate with minor changes in velocity due to variations in density and composition of the rock material.
- In the Earth's crust, P waves can propagate with minor changes depending on the specific properties of the crustal rocks.

In summary, S waves cannot travel through the Earth's liquid outer core, and both S and P waves experience changes in velocity and direction as they pass through different layers of the Earth due to variations in density and composition.