The seismic wave that travels through solids only is the S-wave, also known as the secondary wave or shear wave.

Here's why:

* S-waves are transverse waves, meaning they cause particles to move perpendicular to the direction the wave is traveling. This motion requires a rigid structure, which is why S-waves can only travel through solids.

* P-waves (primary waves) are longitudinal waves, meaning particles move parallel to the direction the wave travels. This type of motion can occur in solids, liquids, and gases.

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