I came here to find the same answer >.< .... Science is hard!!! lol
A Pwave is the first wave to arrive during an earthquake, P waves compress and then expand. They can damage buildings.
ECG records electrical activity and not mechanical, hence it has nothing to do with contraction. But P wave represents atrial depolarization.
The biggest seismic waves are surface waves, which travel along the Earth's surface and are usually the most destructive during an earthquake. The two main types of surface waves are Rayleigh waves and Love waves. Rayleigh waves cause the ground to move elliptically in vertical and horizontal directions, while Love waves cause horizontal shearing motion.
p wave comes first s wave comes next and last comes surface wave.