Deformation analysis in landslides NE Bulgaria using GNSS data complemented by InSAR for better interpretation results

The Bulgarian northern Black Sea coast is affected by many landslides. Landslide research is important as these phenomena cause loss of human lives and infrastructural damages. For this study a landslide area called "Dalgiya yar" was selected. The objective of this study is to provide solid grounds for monitoring the landslide processes using GNSS and SAR data. To achieve the set goals a geodynamic network was established. Those networks consist generally of two types of points – reference (located on geologically stable terrain) and survey points located within the landslide. The overall deformation analysis of the geodynamic networks is done after the third measurement cycle. The main approach to obtain the final results is based on determination of deformation components of spatially oriented triangles. For the studied period and for the mentioned area three main types of deformations have been determined by Finite Elements Method – station displacements, relative side deformations and relative principal deformations. It needs to be mentioned that due to peculiarities of the researched zone the condition that the final elements must to be configured approximately as equilateral triangles with approximately equal areas and not overlapping was not possible to be met. This is the reason to complement the GNNS results with such produced by DInSAR processing of Sentinel-1 data for the mentioned periods.