Determination of Shifts of the Earth Crust in the Surroundings of Skopje by aid of MAKPOS's Reference GNSS Stations

Sa？etak In Macedonia 14 GNSS reference stations have been set up, which are included in the MAKPOS position system. On these, GNSS receivers of the Leica Geosystem type receive radio signals from the GNSS satellites from 0 to 24 hours and send them directly to the computer centre where they are processed. However, after the processing of received signals at the reference GNSS stations using Bernese scientific software, the precision of the specified reference position coordinates per nearly 1.5 mm can be obtained. This high precision is possible to be used to determine the Earth's crust movement. Therefore, in the work were analysing the amounts of Earth's displacement of 4 MAKPOS GNSS reference stations: Skopje, Tetovo, Kumanovo and Veles: - in horizontal sense with N coordinates (north oriented) and coordinates E (oriented towards the east) as well as - in vertically sense by changing their ellipsoidal heights. ？ Coordinate differences and the differences in ellipsoidal heights for the 4 MAKPOS reference stations were calculated since 1. 1. 2011 (when MAKPOS's position system was started) by 10. 9. 2016, that is until was the earthquake in Skopje 11. 9. 2016. ？ In order to determine if there were some significant movements of the Earth's crust after the earthquake in the vicinity of Skopje, the coordinate differences and differences between the ellipsoid heights of the MAKPOS stations were calculated in the time period of 10. 9. 2016 until 12. 9. 2016. It was found that after the earthquake there was not real shift of the Earth's crust in the horizontal direction, but there was a slight change in height and probably the station in Skopje was slightly raised. ？ Differences between coordinates and ellipsoid heights since 1. 1. 2011 were also investigated until 20. 9. 2016 that is up to 9 days after the earthquake in Skopje. Based on the performed comparison and analysis, it can be said that the coordinates of the differences were still in the range as they were until 10. 9. 2016. However, ellipsoid heights again began to descend to the height before the earthquake. Results from this paper should be embedded in the program UNAVCO Plate Motion Calculator