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Acta Geodynamica et Geomaterialia

Author: Trojanowicz Marek
DOI: 10.13168/AGG.2019.0025
Journal: Acta Geodynamica et Geomaterialia, Vol. 16, No. 3 (195), Prague 2019
Full Text: PDF file (0.6 MB)
Keywords: geodetic application of geophysical techniques; disturbing potential model; local quasigeoid modelling
Abstract: The presented paper investigates the local quasigeoid modelling based on the geophysical gravity data inversion (GGI method). The calculations performed indicate a very high accuracy of the derived quasieoid model which is developed when the modelling process is carried out using a global geopotential model. In this case, the local model of disturbing potential (model of type A) is in the form of , where is the part of the model containing the density model, is the polynomial part and is the part determined from a global model. If the global model is not included in the calculations (this is a type B model), the disturbing potential will be . The accuracy of the quasigeoid in latter model is significantly worse. Both types of models contain information about Earth’s crust density changes; however, only for the type B model we can expect that they correspond to real changes; whereas in the type A model the main information about density changes is contained in the part. So the type B model can be seen as a local, integrated model of both the external gravity field and the density distribution of the Earth's crust. Let us note that the GGI method is only used as a quasigeoid modelling method without geophysical or geological interpretation of the density model parameters. Regarding this, we can notice two problems related to the further development of the GGI method. The first concerns the relation of the GGI density model with geological information. The second problem refers to the possibility of increasing the accuracy of the type B quasigeoid model to the level of the A-type model. For the first problem, we demonstrate that the borders of density changes for the masses lying between the geoid and the Moho surface reflect the geological units surprisingly well. The test calculations relating to second problem, consist of determining the type B model using a certain initial model . There were three initial models adopted in the analysis. Results of the analysis indicates that this procedure increases the accuracy of the type B quasigeoid model, although the accuracy of the A-type model is still better.