1. A plot (often in polar coordinates) of the relative intensity versus direction of an outgoing seismic wave such as that resulting from a directional charge or from a source pattern; see Figure D-15a. The directivity results from the interference of the waves from the various components of the pattern. 2. A plot of the relative response of a geophone pattern or of directivity resulting from mixing; see Figure D-15b. Directivity graphs may be specified in various units (apparent velocity for a certain frequency, apparent wavelength, frequency arriving from a certain direction, apparent velocity, etc.), as indicated in Figure D-15b. The vertical scale is often logarithmic (i.e., given in dB) rather than linear. The effect on wavelets can be very different from the effect on a sinusoidal wavetrain so that use of steady-state patterns can be misleading. A plot in f-k space is a form of directivity graph showing also the frequency-dependency. See also Figure C-3.