Surface deformations resulting from tectonic movements can be detected through statistical analyses. Deformations occurring on a surface can be computed independently of time using a model of static deformation. Besides, deformations can be obtained independently of the datum with the strain analyses and interpreted geometrically. Strain is defined as the ratio of the displacements at station points caused by a force to the initial coordinate values. Dilation and shear strains are used for the geometrical interpretation of the deformations. While dilation affects perpendicular to a surface, shear strain affects parallel to a surface. In any geodetic network, strains can emerge due to both the internal structure of the network and the external factors. Strains related to the internal structure of the network are affected by the observation plan and the weights of the observations. Besides, strains caused by external factors occur due to tectonic movements. In this study, the deformations caused by the earthquakes with magnitudes of Mw 7.7 and Mw 7.6 in Kahramanmaraş on February 6, 2023, have been analyzed. For this purpose, three different geodetic networks have been generated using Turkish National Permanent GNSS Network-Active (TNPGN-Active) stations. Observations obtained before and after earthquakes have been evaluated in two different epochs. In each epoch, the observation plan obtained by the Delaunay triangulation, the number of stations, and the initial coordinates are constant. In the geodetic networks, the deformations in the triangular surfaces between two epochs were analyzed using the theta-square criterion in the static deformation model. Consequently, comparing the first and third networks reveals that adding new stations to the network plan reduces the deformation test values. On the other hand, the second network has the larger deformation test values and the maximum shear strain on the triangular surfaces that are ANTE-EKZ1-MAR1, MLY1-GURU-EKZ1, EKZ1-TUF1-MAR1, TUF1-EKZ1-GURU, MLY1-EKZ1-ANTE among the three networks. Besides, the triangular surface of MLY1-EKZ1-ANTE has the largest deformation test value. Additionally, 2D strain analyses have been used to geometrical interpretation of the deformation on the triangular surfaces. Shear strains have been calculated using the strain matrices for each triangular surface. Accordingly, the maximum shear strain on the triangular surface, e.g., EKZ1-TUF1-MAR1, exceeds 9000 microstrains in each network plan. Furthermore, the location of the maximum shear strain is the same in three network plans.
Pakize Küreç Nehbit (Thu,) studied this question.