I told you 3 years ago we have a seismologist on staff...you are older now than you were back then.
You cannot isolate a seismic wave.
Without shear motion or a shear wave there cannot be a compressive wave.
A voice coil's initial motion is a polarity of shear the other polarity travels on and thru the material. The air that travels that material in motion is what you hear. The shear velocity and motion of that material is what causes the air to vibrate. There is first shear motion only and then the molecular motion of the air that follows. Super hard materials sound just like that. A little goes a long way. The materials we prefer the sound of, have a shear velocity closer to the speed of sound in air. Ceramic not being of sound mind or sound ear. Lot more for you to find out.
The LIGO is mechanically grounded to Earth. Tom