## 4 Discussion
### Site Effect Differences
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \multirow{2}{*}{**Station**} & \multirow{2}{*}{**Type of Data**} & \multicolumn{3}{c}{**Model Without Intercept**} & \multicolumn{3}{c}{**Model Intercept**} & \\ \cline{3-10}  & & \(\mathbf{a}\pm\Delta\mathbf{a}\) & \(\mathbf{R}^{2}\) & **SEE** & \(\mathbf{a}\pm\Delta\mathbf{a}\) & \(\mathbf{B}\pm\Delta\mathbf{b}\) & \(\mathbf{R}^{2}\) & **SEE** \\ \hline \multirow{2}{*}{Total} & Raw data & (46.2 \(\pm\) 0.6) \(\times\) 10\({}^{-5}\) & 0.93 & 1.6\(\times\) 10\({}^{-5}\) & (40.7 \(\pm\) 1.2) \(\times\) 10\({}^{-5}\) & (5.1 \(\pm\) 1.4) \(\times\) 10\({}^{-6}\) & 0.92 & 1.6 \(\times\) 10\({}^{-5}\) \\ \cline{2-10}  & Corrected data & (129.0 \(\pm\) 1.3) \(\times\) 10\({}^{-5}\) & 0.93 & 5.5 \(\times\) 10\({}^{-6}\) & (93.7 \(\pm\) 2.1) \(\times\) 10\({}^{-5}\) & (1.8 \(\pm\) 0.4) \(\times\) 10\({}^{-6}\) & 0.93 & 5.7 \(\times\) 10\({}^{-6}\) \\ \hline \multirow{2}{*}{IMI} & Raw data & (45.4 \(\pm\) 1.3) \(\times\) 10\({}^{-5}\) & 0.91 & 2.1\(\times\) 10\({}^{-5}\) & (37.3 \(\pm\) 1.4) \(\times\) 10\({}^{-5}\) & (1.7 \(\pm\) 0.6) \(\times\) 10\({}^{-6}\) & 0.89 & 2.3 \(\times\) 10\({}^{-5}\) \\ \cline{2-10}  & Corrected data & (100.8 \(\pm\) 2.4) \(\times\) 10\({}^{-5}\) & 0.93 & 8.7 \(\times\) 10\({}^{-6}\) & (87.4 \(\pm\) 3.1) \(\times\) 10\({}^{-5}\) & (5.4 \(\pm\) 1.2) \(\times\) 10\({}^{-6}\) & 0.88 & 7.9 \(\times\) 10\({}^{-6}\) \\ \hline \multirow{2}{*}{PLA} & Raw data & (50.8 \(\pm\) 1.5) \(\times\) 10\({}^{-5}\) & 0.92 & 1.8 \(\times\) 10\({}^{-6}\) & (42.0 \(\pm\) 1.9) \(\times\) 10\({}^{-5}\) & (1.2 \(\pm\) 0.5) \(\times\) 10\({}^{-6}\) & 0.89 & 1.6 \(\times\) 10\({}^{-6}\) \\ \cline{2-10}  & Corrected data & (129.0 \(\pm\) 3.5) \(\times\) 10\({}^{-5}\) & 0.92 & 9.6\(\times\) 10\({}^{-7}\) & (94.7 \(\pm\) 3.8) \(\times\) 10\({}^{-5}\) & (6.8 \(\pm\) 1.2) \(\times\) 10\({}^{-6}\) & 0.89 & 8.6 \(\times\) 10\({}^{-7}\) \\ \hline \end{tabular}
\end{table} 
Table 4: Regression results. Figure 7: Models of translation and rotation resonance effects with amplified horizontal amplitudes in near-surface and different depth ranges [22,24]. Moreover, a detailed observation indicated the presence of a water body table at a depth of ca. 15 m below the surface. A simple assessment of the H-value for the rotation resonance effect showed that the resonance layer corresponded to the water table depth (Figure 7). Therefore, in the case of the PLA station, the water body did not influence the translational resonance effect but might have changed the nature of the rotational resonance. An in-depth investigation should be carried out to determine which factors (fractures, water bodies, or both) had a tangible impact on the rotational resonance frequency. Detailed surveys about the impact of local small-scale heterogeneities on the rotational motion [49] confirm the explanations presented above. The occurrence of the geological heterogeneities had a real effect on the wavefield gradient measurements: strain and rotation. In contrast, the impact of heterogeneities may be insignificant in the wavefield measurements (i.e., translational acceleration). The effect of the heterogeneities on the rotations can be caused by altering the phase and amplitude of the signal, whose intensity depends mainly on the velocity contrast but not on the spatial extent of the heterogeneities. Therefore, considering the results obtained for the resonance frequency for the IMI station and PLA station, it can be concluded that geological discontinuities change the nature of the rotational motion compared to the translational motion. Consequently, different geological layers can produce the rotational site effect and not the translational. The rotation amplification coefficients for the IMI and PLA stations were more than two times lower than those of the respective translational ones. As was mentioned above, the predictive models of the rotational amplification for the specific geological setting are unknown, and their relation to the translational site effect parameters is unknown.