The type of seismic wave that arrives at the surface first and moves by compressing and expanding the ground like an accordion is called a primary wave (P-wave).

Here's why:

* Fastest: P-waves travel the fastest of all seismic waves.

* Compression: They travel through solids, liquids, and gases by compressing and expanding the material in the direction the wave travels. This is similar to how sound waves travel.

* First Arrival: Because of their speed, P-waves are the first seismic waves to reach a seismograph after an earthquake.

Let me know if you have any other questions!