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The region of southwest Bulgaria is characterized by a large number of fault structures, and the presence of tectonic and seismic activity, thus predetermines the development of dangerous geodynamic processes. This article discusses the estimates of modern movements of the earth's crust obtained from periodic geodetic measurements. They describe the total effect of fast and slow horizontal and vertical movements. Obtaining such estimates, on the order of mm/y, requires determining the coordinates of the points of the geodynamic geodetic networks with millimeter accuracy. Achieving such accuracy is possible only with the help of modern satellite geodetic technologies. GNSS data from five continuously operating reference stations belonging to National GNSS network is used in this research. The raw GNSS measurements for three-year-and-a-half period are processed. Time series with coordinates and mean square errors (north, east and up) and time series with the residuals from multi-year solution are estimated. The time series show very good quality of the solution (the values of nrms are smaller than 0.70). The results for velocities of EPN Densification network, National GPS Network and Geodynamic GPS network around Sofia and Southwest Bulgaria are combined to obtain velocities field in Southwest Bulgaria derived from GNSS measurements. The newly acquired velocity field confirms that the general tendency of movement of the points in the region of Southwest Bulgaria is in the southern direction with respect to stable Eurasia, as a general tendency the velocities increase from North to South. This pattern is in agreement with the extensive movement of southern Bulgaria and northern Greece. The obtained velocity field can be used for further detailed geodynamic and geological investigations of the fault structures in the region. [ABSTRACT FROM AUTHOR]

The Bulgarian northern Black Sea coast is affected by many landslides. Several geodynamic networks have been built to study landslide processes in the northern Black Sea coast. Landslide research is important, as these phenomena can lead to great material damage. Their destructive impact on buildings, engineering structures and disturbances in the resilience of the earth's crust causes enormous economic, environmental, social and other damage, and often takes human lives. A modern tool for monitoring landslides is the application of GNSS measurements, which has an advantage over conventional measurement methods. GNSS data from six continuously operating reference stations from National GNSS network for three years and a half period are processed and analyzed. Time series with coordinates and mean square errors (north, east and up) are obtained. Time series with the residuals from multi-year solution are obtained too. The time series show the very good quality of the solution (the values of nrms are between 0.60 and 0.80). In this study long-term processing of data from continuously operating reference stations (CORS) is performed, to obtain the coordinates and velocities of the stations, because this also affects the local networks built for the study of landslides. The velocities of the points from the National GNSS network in the northern Black Sea region are relatively small, less than 1 mm/year. To obtain the movements of the points from the local geodynamic networks, it is necessary to process their GNSS measurements together with the GNSS measurements from the continuously operating reference stations from National GNSS network but the velocities of the station must be taken in to account, as done in this study. This allows to determine whether the measured points are located in the landslide or outside it and thus to accurately determine landslide boundaries. [ABSTRACT FROM AUTHOR]

The study of recent crustal movements is one of the priority areas of the Earth sciences. Geodetic methods occupy a particularly important place in the general complex of measurements and investigations of crustal movements because they provide quantitative information on the condition and development of geodynamic processes. The paper outlines the newly accepted project with main goal monitoring the geodynamic processes in the area of Sofia. This goal will achieve by periodic GNSS measurements over the Sofia geodynamic network and using data from continuously operating reference stations from National GNSS Network. The study will give estimates of the recent crustal movements in the area; active strain and strain rate and correlation between the crust movements, seismic events and tectonic structures. DInSAR method, based on interferometric images, will also apply to obtain independent estimates of the crustal movements from RSA data. The paper summarizes the geodetic, geological and seismotectonic information about the territory around Sofia obtained up to now. A description of the existing geodynamic geodetic network in the studied area is given and main characteristics of the geological setting are made. The data show the presence of active faults in the area that need to be investigate. The research project can be seen as a new stage in the study of an area with a clear seismic hazard. It is propose to develop current issues related to the joint interpretation of geodetic, geological and seismotectonic information for the assessment of recent geodynamic processes. The expected results will be a contribution to the assessment of natural risk and seismic hazard in the studied area. [ABSTRACT FROM AUTHOR]

Satellite Laser Ranging (SLR) measurements of the geodynamic satellite LAGEOS-1 (LAser GEOdynamics Satellite) for the period January 2000 - June 2013 are processed and analyzed. The analysis are carried out with the Satellite Laser Ranging Processor (SLRP) software, version 4.3, developed in the Department Geodesy of the National Institute of Geophysics, Geodesy and Geography at Bulgarian Academy of Sciences. A new module for parameter estimation using the least squares method was developed to allow flexible treatment and combination of observational equations - from elimination of parameters to sequential estimation. Through sequential estimation, total number of 202 447 measurements are processed and analyzed. Coordinates and velocities of 37 stations located on the main tectonic plates are estimated. Along with the site’s coordinates and velocities, arc dependant parameters, geogravitational parameter - GM, Earth Orientation Parameters (pole coordinates and length of the day - LOD) are also determined. The root mean square of the multiyear solution is 10 cm. The results obtained are contribution to the monitoring of recent tectonics of the major continental plates. [ABSTRACT FROM AUTHOR]