Tests of sommerfeld ground wave theory using ground-penetrating radar pulses

We have used ground-penetrating radar pulse waveforms within moveout profiles that we recorded over dielectric ground, to test the geometric amplitude attenuation rates of interfacial surface air waves predicted by classic Sommerfeld theory. The pulses allow separation of interfacial wave modes. We used horizontally polarized pulses centered from 37-390 MHz, frozen ground, and an intermediate range of tens of wavelengths over which radial polarization is predicted to exhibit anomalously low rates. As predicted, azimuthal broadside polarization at 37-45 MHz attenuated in proportion to the square of range, but the radial endfire rate was closer to the 1.6 power of range. At 360-390 MHz, both rates exhibited predicted range-squared amplitude attenuation. Not readily extractable from the theory are the rates for subsurface direct waves, for which we found, from numerical experiments, that both polarizations attenuate in proportion to the square of range. This suggests that geometric rates for all types of subsurface interfacial waves attenuate in proportion to range squared and could be subtracted from actual rates to determine material loss rates.