Here's why:

* P waves (Primary waves): These are the fastest seismic waves and travel through solids, liquids, and gases. They are compressional waves, meaning they cause particles to move back and forth in the same direction as the wave travels.

* S waves (Secondary waves): These waves are slower than P waves and can only travel through solids. They are shear waves, meaning they cause particles to move perpendicular to the direction the wave travels.

* Surface waves: These waves travel along the Earth's surface and are the slowest of the three types. They are responsible for the most damage during earthquakes. There are two main types:

* Love waves: These waves cause horizontal shaking.

* Rayleigh waves: These waves cause both horizontal and vertical shaking.

Since surface waves travel along the Earth's surface, they are influenced by the properties of the surface material, which slows them down compared to waves traveling through the Earth's interior.