## 3 Results  
### Assessment of Tectonic Coherence Using GNSS Velocities and Plate Motion Benchmarks  
To assess the kinematic integrity of the Korean Peninsula and validate the robustness of GNSS-derived velocity estimates, this section presents a comparative evaluation of horizontal displacement vectors computed using two independent geodetic processing suites--GAMIT/GLOBK and Bernese. By systematically comparing these results with globally recognized plate motion models (ITRF2020, GSRM v2.1, and APKIM2005-IGN), the analysis aims to identify consistent regional motion trends and isolate potential discrepancies attributable to localized tectonic deformation or software-dependent processing differences. These evaluations are critical for establishing a reliable geodetic basis for subsequent strain field derivation and seismic hazard assessment. As a prerequisite for this analysis, although the observation period was relatively short (three years), strain analysis reliability was improved through denser GNSS point distribution. By supplementing existing CORSs with additional geodetic control points, spatial resolution was enhanced, especially around the Yangsan and Ulsan Faults. This approach aligns with prior findings that dense, evenly distributed GNSS networks improve strain estimation accuracy [42; 54; 59]. Figure 5 compares east and north displacement components from GAMIT and Bernese processing at six stations. Despite slight differences (e.g., SUWN: 27.48 vs. 30.76 mm/yr in the east), the east-northeastward trend is consistent across solutions, supporting the interpretation of the Korean Peninsula as a coherent tectonic block. These discrepancies underscore the importance of understanding software-specific effects when deriving strain rates. Figure 5: Time series of east (**left**) and north (**right**) coordinate components from five GNSS stations (SUWN, WULJ, MUJU, KWNJ, and PUSN) in the Korean Peninsula. Each subplot compares daily position estimates processed by GAMIT (blue) and Bernese (red) software packages. Linear trends represent horizontal crustal motion, with velocity estimates (in mm/year) annotated in each plot. To contextualize the observed crustal motion, Figure 6 overlays GNSS-derived velocity vectors onto three global plate motion models--APKIM2005, ITRF2020, and GSRM v2.1--across the Korean Peninsula. The velocity vectors computed from both GAMIT and Bernese processing exhibit high consistency with the model predictions, with magnitudes ranging from 28 to 31 mm/yr and azimuths of approximately 113\({}^{\circ}\) to 116\({}^{\circ}\), indicating a coherent east-northeastward motion. This strong agreement across independent models and processing strategies validates the reliability of GNSS-derived velocities for strain analysis. It also confirms that the Korean Peninsula behaves as a kinematically coherent tectonic block within the overriding plate system. Minor discrepancies between observed and modeled vectors--particularly near plate boundaries or coastal zones--may indicate localized deformation or inelastic strain accumulation. When analyzed at high spatial resolution, these deviations can reveal motion gradients critical for computing precise regional strain tensors. Figure 6: Crustal velocity vectors at GNSS stations in southeastern Korea derived from this study and previous models. Blue and yellow arrows represent velocity results processed using the Bernese and GAMIT software, respectively. For comparison, red arrows indicate velocities based on the APKIM2005-IGN plate model, green arrows show the GSRM v2.1 model, and purple arrows represent ITRF2020-based velocities. All vectors are shown relative to a stable Eurasian reference frame. The map highlights variations in crustal motion near major active faults, including the Yangsan and Ulsan faults (marked in red), where deviations between modeled and observed velocities may indicate localized deformation or tectonic strain accumulation. The inset map provides regional tectonic context, including surrounding plates and microplates.