# Monitoring of Possible Activities of Yangsan Fault Zone Using GNSS
## 5 Conclusions  
In this paper, we analyzed the crustal displacement and stress change for the purpose of confirming and monitoring the stabilization of the crustal movement of the Yangsan Fault, using observation data collected from 24 GNSS observation stations in Korea for about 3 years.  
1. Based on the results of this study, the Yangsan Fault Zone is moving about 30 mm per year to the southeast. This is like the annual movement of the Korean Peninsula. The period was subdivided to see trends the tectonic movement. When divided into two periods, both the magnitude and direction of crustal movement were similar for two sub-periods: between 2018 and 2019, and between 2020 and 2021. The stations on both sides, east and west, divided by the Yangsan Fault Zone, moved with similar scale and direction.
2. Internal deformation was monitored to analyze the stability of the fault in more detail. As a result, most of the stations around the study area moved in the northwest direction with respect to GKPG at a very small magnitude, average of about 1.8 mm/year. Considering that all of them are very small and move in the same direction, it is judged that there is no clear distortion of the crust inside the Yangsan Fault. Since the scale is close to the average values of the Korean Peninsula, it is considered stable at the moment. However, the internal distortion is very important to understand the movement of the region, which should be further investigated in near future.
3. The stress of the fault was computed through GNSS data. Based on the calculated stress, the scale of the east-west expansion during the period decreased over time. In addition, the stress strain of the area of interest is larger than that of surrounding triangular networks. However, based on the rate of change in the baseline distance, the area that is expected to have crustal deformation appears to be stable at present, which is additional evidence that the study area is in a stable state.  
Due to the nature of crustal displacement, continuous research and monitoring through long-term data processing is necessary. In addition, further research is needed on the relationship of whether the fault is the primary reason for the earthquakes occurring in that region or not. The method proposed in this study can be applied to other zones in Korea to analyze the stress of the fault. It is also believed that the stress analysis is a beneficial source of data for earthquake prediction.  
Conceptualization, H.-U.K. and T.-S.B.; methodology, H.-U.K.; software, H.-U.K.; validation, H.-U.K. and T.-S.B.; formal analysis, H.-U.K.; investigation, H.-U.K.; resources, H.-U.K.; data curation, H.-U.K.; writing--original draft preparation, H.-U.K.; writing--review and editing, H.-U.K.; visualization, H.-U.K.; supervision, T.-S.B.; project administration, T.-S.B.; funding acquisition, T.-S.B. All authors have read and agreed to the published version of the manuscript.  
This research was supported by a grant from National R&D Project \"Development of ground-based centimeter-level maritime precise PNT technologies\" funded by the Ministry of Oceans and Fisheries (1525012253).  
Not applicable.  
The authors would like to thank the National Geographic Information Institute (NGII) of Korea for providing the observation data used in this experiment.  
The authors declare no conflict of interest.