Short Wavelength Influence of Far and Deep Sources on High-accuracy Gravity Modelling

Gravitational sources generating very long wavelength effects, if observed at uniform elevation, may also induce short wavelength effects, if observed at varying elevations. This property is due to the vertical gradient effect of these sources. The magnitude of this effect is investigated for its relevant sources: large local, but shallow ones, as well as far topographic (> 167 km) and deep sources. Global maps will be shown and indicate that mountainous regions and oceans (for spherically reduced Bouguer data) are most susceptible to this problem and quantify this effect. These maps also allow to identify other regions where high-accuracy gravity observations need to account for it, e.g. for exploration purposes. Other topics significantly related to this “far field effect” are: merging terrestrial and aero data, its application as a prerequisite for data transformation by means of, e.g., equivalent source or Fourier methods, and its influence on model interpretation.