Think of it like a slinky: if you push one end of the slinky forward, the coils will compress together. This compression travels down the slinky, and the coils move back and forth in the same direction that the compression is moving.
Similarly, in a P-wave, the ground compresses and expands as the wave passes through it. The particles oscillate in the same direction as the wave's propagation. This compressional motion is why P-waves are also called primary waves.
Here's a visual breakdown:
* Direction of wave travel: →
* Particle movement: ← → ← →
P-waves are the fastest type of seismic wave and are the first to arrive at a seismograph after an earthquake.
