## 2 Geodetic Monitoring of Co-Seismic Displacement  
This paper focuses on a method to detect co-seismic static displacement during an earthquake by using precise positioning based on GNSS. We aim to provide a detailed description of the method used. [PERSON] et al. [13] applied the results of this method without giving any details of the method and [PERSON] et al. [14] only applied the results of the method as data in supplements without giving any details. The method is based on the application of data from permanent GNSS stations, which continuously observe GNSS satellites. Based upon the results of these observations, the coordinates of the monitored stations in the global coordinate system can be determined at given intervals, and a time series of coordinates can be prepared and analysed. As discussed by [PERSON] and [PERSON] [15], the time series of coordinates usually contain secular trends, annual oscillations, and rapid jumps. In case of an earthquake, the co-seismic static displacement of stations is calculated from the difference of the station position before and after the seismic event. The co-seismic displacement can be determined when analysing the time series before and after the earthquake. If a short part of the time series (i.e., two months maximum) is used, the secular trends and annual oscillations can be eliminated. GNSS technology offers a variety of options to detect offsets. One type of GNSS data processing is the \"relative network solution\" method, where station coordinates are determined relative to reference stations located outside of an earthquake area. The deformation signal (i.e., co-seismic displacement) can also be extracted by analysing data from the entire GNSS network simultaneously using free-net solutions. [PERSON] et al. [16] used relative network solutions from the GAMIT/GLOBK software package and a Kalmanfilter to determine coordinates and to detect the rate of change in the station position. [PERSON] et al. [17] introduced a method to extract spatially and temporally coherent signals by analysing data from the entire GNSS network simultaneously using free-net solutions. In this method, the deformation signal is extracted by analysing the change of the GNSS geometry net-form, integrating the location, baseline length, and directional information from all GNSS stations over the entire network. This is then combined with area strain, and the deformation characteristic is then further interpreted. When high-rate (10 Hz) recording GNSS receivers and accelerometers are located close to the fault where an earthquake occurs, the co-seismic dynamic shifts can be analysed [4]. However, this supposes the availability of a very dense network of high-rate GNSS stations and accelerometers. Our aim was to analyse the data from a single station or from a few (2-5) stations in a large area around an earthquake hypocentre. Our method design was based on an approach different from the above-mentioned methods and our focus was based on the determination of coordinates using the PPP (Precise Point Positioning) method. From a comparison of the two methods, PPP and a \"relative network solution\", [PERSON] et al. [18] concluded that virtually identical results are achieved using both methods. In order to achieve the required positional accuracy, data from a single day was used. This means that the coordinates of the permanent station were determined every day. [PERSON] et al. [19] noted that by using a kinematic precise point positioning strategy to determine co-seismic deformation within 12 h after an earthquake, the co-seismic displacement data may also contain early post-seismic deformation. This must not be overlooked during the evaluation of results. An anharmonic analysis (described in more detail in Section 3) was used to analyse the time series of coordinate components (North, East, Up).