The strongest Earthquake Waves

An earthquake is caused when energy is suddenly released from a point called hypo-center in the form of spherical seismic waves that travel in all directions outward. The point on the Earth's surface directly above the focus is termed the epicenter. 

These seismic waves are of two different types: Body waves and Surface waves. 

1) Body waves are seismic waves that travel through the lithosphere. Two kinds of body waves exist: P-waves and S-waves. 

i) P-waves (Primary waves) are longitudinal waves just like the sound ways causing compression and expansion of the medium they pass through. They can travel through all forms of matter i.e. solid, liquid and gases. P waves are pressure waves that travel faster than other waves through the earth to arrive at seismograph stations first, hence the name "Primary".

Typical speeds are 330 m/s in air, 1450 m/s in water and about 5000 m/s in granite.

ii) S-waves (Secondary waves) are transverse waves just like the light waves shaking the medium back and forth perpendicular to the direction they pass through. They can travel only through solids with speed around 60% of that of P-waves in any given material. Amplitudes of S waves are generally about five times larger than those of P waves, so much stronger. 

2) Surface waves travel at or near the Earth's surface. These waves produce a rolling or swaying motion causing the Earth's surface to behave like waves on the ocean. The velocity of these waves is slower than body waves. Because of their slow speed, these waves are particularly destructive to human construction because they cause considerable ground movement. They are also of 2 types:

i) Rayleigh waves: travel as ripples with motions that are similar to those of waves on the surface of water. Roughly 90% of the velocity of S waves. 

ii) Love waves are horizontally polarized shear waves (SH waves), existing only in the presence of a semi-infinite medium overlain by an upper layer of finite thickness.

Surface waves are stronger than body waves with amplitudes in meters. The strongest of all are Rayleigh waves with maximum amplitude and min. velocity.