A seismic source radiates different types of seismic wave with different amplitude decays. Some of these seismic waves can only be observed in the vicinity of the source. In theoretical seismology usually all seismic wave types with an amplitude decay of r-1 , are called “far-field” terms, while those with a amplitude decay of r-2 are called “near-field” terms. If the hypocentral distance is large enough for the “near field” terms to become negligible one is in the “far field”. The exact hypocentral distance, which separates “far field” and “near field”, depends on the frequency of the seismic waves. Usually a distance of a few wavelengths from the source is considered as “far field”, and a distance within a fraction of a wavelength is “near field”, with intermediate distances requiring the examination of the effects of the individual terms (Aki and Richards, 1980, p. 88 and eqns. 4.23 and 4.35). However, in geology and earthquake engineering a simpler approach is taken: Locations more than about ten source dimensions from the source are in the far field, and those within one to several dimensions are in the near field