Love wave
From Wikipedia, the free encyclopedia
In elastodynamics, Love waves are essentially horizontally polarized shear waves (SH waves) guided by an elastic layer, which is "welded" to an elastic half space on one side and borders vacuum on the other side. In seismology, Love waves (also named Q waves) are surface seismic waves that cause horizontal shifting of the earth during an earthquake. A.E.H. Love predicted the existence of Love waves mathematically in 1911; the name comes from him. They form a distinct class, different from other types of seismic waves, such as P-waves and S-waves (both body waves), or Rayleigh waves (another type of surface wave). Love waves travel with a slower velocity than P- or S- waves, but faster than Rayleigh waves.
[edit] Description
The particle motion of a Love wave forms a horizontal circle or ellipse moving in the direction of propagation. Moving deeper into the material, motion decreases to a "node" and then alternately increases and decreases as one examines deeper layers of particles. The amplitude, or maximum particle motion, decreases rapidly as one examines deeper layers of particles.
Since Love waves travel on the Earth's surface, the strength (or amplitude) of the waves decreases exponentially with the depth of the earthquake. However, given their confinement to the surface, their amplitude decays only as 
, where r represents the distance the wave has traveled from the earthquake. Surface waves therefore decay more slowly with distance than do body waves, which travel in three dimensions. Large earthquakes may generate Love waves that travel around the Earth several times before dissipating.
Love waves take so long to dissipate due to the huge amount of energy that they contain. For this reason, they are the most destructive within the immediate area of the focus or epicentre of an earthquake. They are what most people feel directly during an earthquake.
In the past, it was often thought that animals like cats and dogs could predict an earthquake before it happened. However, they are simply more sensitive to ground vibrations than humans and can detect the subtler waves that precede the Love waves, like the P-waves and the S-waves.
