Answer to Puzzle Contest (from the winner):

"S-Wave, P-Wave or L-Wave.

P waves (Primary or Push) - fast energetic shock waves that travel through liquids and solids, vibrating the rocks in the direction of wave travel. Simulate by pushing water down a bath from the tap end - a big wave arrives at the other end in a second or two. P waves can travel right round the earth after an earthquake.

S waves (Secondary or Shear) - slightly slower waves that vibrate the rock at right angles to the direction of travel. These rely on the shear strength of rock to travel. They can therefore only travel through solids since molten material has no shear strength. Simulate by pushing water across the tap end of a bath. No clear wave arrives at the other end.

L- waves (including Love and Rayleigh waves) - these are the slowest, least energetic and most spatially restricted of the earthquake waves yet they do most damage. These waves are the actual ground motion at the surface. Love waves move buildings from side to side. Rayleigh waves move them up and down. The combined motion is extremely destructive to masonary structures."

I was just going for the S variety, but heck monkey, I like this complete set better!

Winner: Graeme Black, Vacaville, CA