View of 3-D grid used to illustrate seismic wave propagation. The mesh (grid) represents a volume of elastic material through which waves can propagate in the direction shown. The 3-D grid is shown in perspective view to demonstrate the wave propagation effects and particle motions of the different wave types in all directions. In the animations shown below, Compressional, Shear, Rayleigh and Love wave propagation through the elastic material is illustrated. In this 3-D volume, the grid is designed to have an upper surface (corresponding to the Earth’s surface) that consists of a boundary with a vacuum or very low density fluid above so that surface wave propagation (Rayleigh and Love waves) as well as body wave propagation (Compressional and Shear waves) can be illustrated.
All wave types are designed to propagate in the X direction and parallel to the Earth’s surface. The wave animations illustrate wave characteristics and particle motion as listed in Table 1. However, no decrease in energy or amplitude with distance due to spreading out of the wave energy (geometrical spreading) or loss of amplitude caused by absorption of energy (sometimes called attenuation) by the media (due to anelasticity) are included. The elastic material is also assumed to be isotropic (velocity and other physical properties are the same for all directions of propagation), therefore, no anisotropy is included in the animations. Furthermore, for the surface wave animations, no dispersion (variation in wave velocity with frequency) has been included. The seismic wave animations were created using a Matlab code and then converted to an animated GIF format.