Hello, I'm an expert in seismology with a strong background in understanding the behavior of seismic waves. Let's dive into the topic of S waves.

S waves, also known as Secondary waves or Shear waves, are a type of elastic seismic wave that occurs during an earthquake. They travel only through solids, not liquids or gases. This is because S waves involve the distortion of the material through which they are passing. In contrast, the Earth's outer core and the entire mantle are solid, so S waves can travel through these regions.

S waves have a characteristic transverse motion, meaning they move particles from side to side as they propagate. This is different from P waves (Primary waves), which have a longitudinal motion, moving particles back and forth in the direction of the wave's travel.

When an earthquake occurs, P waves are typically felt first because they travel faster than S waves. However, because S waves cannot travel through the liquid outer core, they are not detected on the opposite side of the Earth from the earthquake's epicenter. This is why seismologists can use the absence or presence of S waves to help determine the depth of an earthquake's focus.

To summarize, S waves travel through the Earth's solid materials, including the crust and the mantle, but they are absent in regions where the Earth is liquid, such as the outer core.

read more >>

Both types of seismic wave can be detected near the earthquake centre but only P-waves can be detected on the other side of the Earth. This is because P-waves can travel through solids and liquids whereas S-waves can only travel through solids. This means the liquid part of the core blocks the passage of S-waves.read more >>