In 1999, the Izmit Earthquake struck Istanbul and its surroundings in northwest Turkey. It was one of the most devastating earthquakes of the twentieth century, significantly impacting on 20 million inhabitants and nearly half of the country’s industry. The earthquake’s epicentre was located on the North Anatolian Fault (NAF) which is one of the most active right-lateral strike-slip fault. Because of its importance for the tectonics of Marmara region, the Izmit earthquake has attracted the interest of several scientist to study the surface deformation during earthquake cycles. This study examines the Izmit earthquake using Interferometric Synthetic Aperture Radar (InSAR) with Global Navigation Satellite System (GNSS) and Coulomb Stress Change Modelling. Since the InSAR and GNSS techniques are sensitive to displacement , the technique is very efficient to measure “earthquake deformation” phenomenon. Moreover, by combining these techniques with Coulomb Stress Change Modelling, the understanding of complex deforming zones can be improved. From a joint analysis of InSAR, GNSS and Coulomb Stress Modelling techniques, the interseismic, coseismic and postseismic deformation of the 17 August 1999 Izmit earthquake have been determined in terms of stress progression and displacement. The results of the research show that there is an apparent correlation between the InSAR, GPS and Coulomb Stress Change Modelling results, which contribute to the identification of the Izmit earthquake characteristics. It shows that the Izmit earthquake caused the northern part of the NAF to move in an easterly direction and the southern part to move in a westerly direction. This partially explains the fault extended westwards of the surface faults, underneath of the Gulf of Izmit. In addition, this westerly movement changed the stress distribution and increased the deformation around the fault zone. The conclusion can also be drawn that combination of these three techniques can improve the understanding of the behaviour of the earthquakes and highly damaged areas. Following an in-depth multi-dimensional analysis of research results, recommendations for hazard mitigation can also be presented.