The potential of a novel gravity research method in geophysics

Abstract

The gravity force, as a vector, has both magnitude (length) and direction. Previously, with the measurement methods employed, only the magnitude (length) of the vector was measured; there was no possibility in geophysical practice to measure the direction of the vector. Previously, the method of astronomic positioning was used to determine the vertical direction. This was extremely time-consuming, taking several months, complex and expensive procedure, used in geodesy at some points to determine the values of vertical deflection. Recently, revolutionary changes have been made in this area, with the development of a new, quick and simple method for determining the local vertical direction, which is more accurate than ever before. In contrast to the previous extremely slow process, with the computer-controlled, fully automated QDaedalus measurement system, a single person can perform multiple high-precision measurements at various locations overnight, making the appropriate quantity and quality of measurement results suitable for geophysical structural research purposes. In this article, we briefly describe the operation of the QDaedalus system and draw attention to the geophysical applicability of the method in terms of detectable mass anomalies and useful station spacing using astrogeodetic field measurements. To demonstrate this, astrogeodetic measurements were also carried out along a 4 km long section, from which the deflection of the vertical values and geoid heights were determined. Our measurements were compared with the normal values calculated with the global gravity model of high resolution (Global Gravity Model plus). As the deflection of the vertical values calculated with this model includes the effect of the surface topographic masses at the resolution of the model, the difference between the measured and the modelled values is practically a function of subsurface density anomalies. At the same time, we performed model calculations showing how density anomalies of different extents assumed at different depths affect the value of the vertical deflections and the geoid anomalies.