## 3 Results
### Strain Tensor Analysis and Spatial Characterization of Deformation
Black bars represent the absolute magnitudes of maximum shear strain within each triangular element, with lengths scaled to the strain rate (\(\upmu\)strain/yr). Red lines mark the Yangsan Fault (western trace) and the Ulsan Fault (eastern trace). The maps reveal spatial and temporal variations in localized shear deformation, with consistently elevated strain accumulation observed near the central segment of the Yangsan Fault. The network includes 23 geodetic control points (blue squares) and 10 CORS (black circles). significant differences in shear stress direction can be observed when comparing Triangle 16 with nearby sites. Comparison of Triangle 16 and Triangle 17:  
* Triangle 16:
* Shear Stress Direction: 87.31\({}^{\circ}\)
* Maximum Shear Strain: 1.675 ustrain/yr
* Principal Strain: 0.107 ustrain/yr and \(-\)1.568 ustrain/yr
* Triangle 17:
* Shear Stress Direction: 33.32\({}^{\circ}\)
* Maximum Shear Strain: 0.976 ustrain/yr
* Principal Strain: \(-\)0.327 ustrain/yr and \(-\)1.304 ustrain/yr  
The shear stress direction difference between Triangle 16 and Triangle 17 is 53.99\({}^{\circ}\). This substantial difference indicates a concentration of shear stress at Triangle 16, which lies near the Yangsan Fault, suggesting the potential for active faulting. In contrast, Triangle 17 exhibits a significantly lower shear stress direction, implying different deformation characteristics and potentially lower seismic hazard. The large difference in shear stress direction at Triangle 16 indicates a region closer to the fault's primary deformation axis, where fault reactivation is more likely. Comparison of Triangle 16 and Triangle 8:  
* Triangle 16:
* Shear Stress Direction: 87.31\({}^{\circ}\)
* Maximum Shear Strain: 1.675 ustrain/yr
* Principal Strain: 0.107 ustrain/yr and \(-\)1.568 ustrain/yr
* Triangle 8:
* Shear Stress Direction: 25.81\({}^{\circ}\)
* Maximum Shear Strain: 1.133 ustrain/yr
* Principal Strain: 0.535 ustrain/yr and \(-\)0.598 ustrain/yr  
The shear stress direction difference between Triangle 16 and Triangle 8 is 61.50\({}^{\circ}\), reflecting a sharp rotation in shear stress direction at Triangle 16. Triangle 8, on the other hand, shows a much lower shear stress direction, suggesting that it is situated in a region with relatively lower shear stress accumulation. This indicates a notable difference in the underlying crustal deformation mechanisms. Triangle 16, located closer to the Yangsan Fault's center, shows concentrated shear stress, while Triangle 8 represents a region with relatively less deformation and weaker shear stress orientation. Figure 9 visualizes the maximum shear strain, with the highest shear strain (2.984 ustrain/yr) observed in Triangle 10. This emphasizes concentrated deformation along fault zones, particularly around the Yangsan Fault. Regions such as Triangle 45, exhibiting high strain, suggest localized extension, indicative of evolving fault dynamics. These findings highlight changes in fault behavior and the potential for significant deformation in the near future. In this context, significant differences in shear stress direction can be observed between Triangle 16 and nearby regions, as follows:  
Comparison of Triangle 16 and Triangle 17:  
* Triangle 16:
* Shear Stress Direction (\(\theta_{7\text{max}}\)): 87.59\({}^{\circ}\)
* Maximum Shear Strain: 2.325 ustrain/yr
* Principal Strain: 0.107 ustrain/yr and \(-\)1.568 ustrain/yr
* Triangle 17:
* Shear Stress Direction (\(\theta_{7\text{max}}\)): 33.32* Maximum Shear Strain: 0.976 \(\upmu\)strain/yr
* Principal Strain: \(-0.327\) \(\upmu\)strain/yr and \(-1.304\) \(\upmu\)strain/yr  
The 54.27\({}^{\circ}\) difference in shear stress direction between Triangle 16 and Triangle 17 indicates a region of concentrated shear stress at Triangle 16, which lies at the boundary where the Yangsan and Ulsan faults diverge. This suggests a higher potential for fault reactivation and seismic hazard at Triangle 16, as compared to Triangle 17, which exhibits a significantly lower shear stress direction.