GNSS MONITORING OF THE GEODYNAMIC PROCESSES IN THE AREA OF SOFIA AN IMPORTANT TOOL FOR STUDYING OF RECENT GEODYNAMICS AND NATURAL RISK PREVENTION IN A HIGHLY POPULATED AREA

Abstract

In recent years GNSS studies play an increasing role in studding of natural risk hazards and active tectonics. The area of Sofia is part of the broad South-Balkan Extensional Tectonic System. This highly populated area of economic significance, even showing to be not so active as other parts of the System is also affected by natural hazards, as active seismicity, landslides, rock falls, debris, etc. GNSS studies are extremely important for understanding of natural hazards and recent geodynamics of the area, especially establishing and investigating of active faults, which is crucial for the prognostic and evaluation of the seismic risk. In aim to perform GNSS Monitoring in the area of Sofia and all over the territory of Bulgaria the Department of Geodesy at National Institute of Geophysics, Geodesy and Geography maintains the National Permanent GNSS. To study the modern movements of the Earth's crust during the period 1996-1997, a geodynamic network was built in the area around Sofia, covering South Western Bulgaria. The network is designed for highprecision GNSS measurements, determination of coordinates and velocities of points, calculation of active strain in the area and long-term monitoring crustal movements. The processing and analysis of the measurements allow monitoring of recent movements of the earth's crust in Bulgaria and the Balkan Peninsula and, together with seismic and geological information, an assessment of seismic and geological hazards. The results obtained from the analysis of GNSS data of Sofia area and SW Bulgaria allow to identify new area of probably active faults, provide new data on known tectonic structures and have a significant implication in the study of recent crustal movements and evaluation of the natural hazard in the region.