## 6 Analysis and Results
### Geomorphology Maps for V\({}_{\text{S30}}\) Representation  
In this section, the suitability of the PBC and OBC base maps for representing V\({}_{\text{S30}}\) is discussed. The geomorphology map from PBC in this study was generated based on the methodology from the study of [PERSON] and [PERSON] (2007) with different classification factors (see Section 6.1), while the geomorphology map from OBC was from [PERSON] et al.'s (2018) results [9; 50]. Both the PBC and OBC geomorphological maps utilized the same geo-signature indices, i.e., slope, convexity, and texture. However, the procedural differences resulted in a different number of geomorphological units in the output. The comparisons and descriptions of the PBC and OBC units are shown in Figure 4. The number of classes in high sedimentation areas is higher in the PBC map.  
Each unit from PBC and OBC was plotted against the V\({}_{\text{S30}}\) values (see Figures 6 and 7). Notably, not all of the geomorphological units can be determined because the observations were insufficient due to site accessibility. Some of the geomorphological units that were statistically unusable, which were mostly located on steep slopes or in forested areas, were excluded. The V\({}_{\text{S30}}\) plot focused on the NEHRP provision class due to the same amplification behavior property. The standard deviation of the unit classes is considered to be a better proxy for identifying the property based on V\({}_{\text{S30}}\) values. Hence, the statistical analysis was also applied.  
From the observations, the PBC geomorphological units (see Figure 7) have lower standard deviations than the OBC (see Figure 8). Therefore, the PBC geomorphological map was selected for further analysis. A significance test was performed to test whether the selected representative unit was meaningful. Based on the data characteristics, a nonparametric significance test and the Kruskal-Wallis test were applied for the geomorphology groups representing abilities [57]. At a confidence limit of 95% (\(p\)-value \(<\) 0.005), the \(p\)-values of the significance tests for the units from PBC and OBC were 0.004319 and 0.03096, respectively. However, some units were eliminated due to an insufficient number of observations, and some units were also eliminated if their values were higher than the absolute standard deviation. The significance test results showed that the PBC units represented the V\({}_{\text{S30}}\) value at a significant level. Hence, the correlation between the PBC and OBC geomorphological units and the V\({}_{\text{S30}}\) values was obtained using the statistical computing package Cocor in R programming language [58]. The correlation between the V\({}_{\text{S30}}\) and PBC geomorphological units was 0.01539, while that of the V\({}_{\text{S30}}\) and OBC geomorphological units was \(-\)0.354. A correlation test was also conducted at a confidence level of 95%. The null hypothesis was \"if the correlation numbers between the V\({}_{\text{S30}}\) and PBC geomorphological unit and the V\({}_{\text{S30}}\) and OBC geomorphological unit are equal\". From [PERSON]'s set of hypothesis testing based on the results of the Cocor method, the null hypothesis was rejected. Therefore, the correlation between the V\({}_{\text{S30}}\) and the PBC geomorphological unit was higher than that of the V\({}_{\text{S30}}\) and the OBC geomorphological unit.  
Figure 6: Geomorphology map for AOI2 obtained using a 250-m resolution DEM (Figure 2(ii)).