Changes of gravity influenced by water level fluctuations, based on measurements and model computations (original) (raw)

More than 70% of the Earth's surface is covered by water. The outward form of this enormous volume of water is extremely variable. The majority is represented by oceans, seas and rivers but the quantity represented by subterranean water, arctic ice and precipitation (rain, snow) as well as that accumulated by human activity in reservoirs is not neglectable either. The influence of these volumes of water on the gravity field can be grouped in several ways: according to areal extension (global, regional, local), according to the causes producing the effects (tide, geodynamical processes, human activity), or according to the temporal variation of the causes (periodic, secular). In our paper we are presenting the results of our gravity measurements investigating the influence of local water-table variations, the daily variation of the quantity of water in an 80000 m 3 urban reservoir, and the water-level fluctuations of the Danube. For the field work two LCR-G gravimeters were used, engineering geophysical soundings were carried out (using a penetrometer), and the available water-level observations of the region were analyzed. For modeling we have computed the gravity effects either by supposing a Bouguer plate or by decomposing the irregular body into a series of regular bodies. The effect of water masses on the topographic correction was also modeled. The results can be useful in selecting localities for stations of a gravity base network or for studying secular variations of the gravity field by repeated measurements.