## 3 Results  
### Parameters of Strong Ground Motion  
In this study, a broad range of strong-motion parameters has been estimated and analyzed. The results from the main event records are presented in a tabulated form (see Table 1). The results are discussed in light of their dependence upon the frequency content of the recorded accelerograms. The comparison of the main parameters in the basement and on the sixth floor, as shown in Table 1, reveals that the PGA on the sixth floor exhibits significantly higher values in all components (EW, NS, and UD) compared to the basement. The PGV and Peak Floor Acceleration (PFV) values vary considerably between the basement and the sixth floor, with the sixth floor showing higher values for all components than the basement. The same tendencies are found for PGD and Peak Floor Displacement (PFD). The amplification of PFA SGL2 (sixth floor) versus PGA SGL1 (basement) shows significant value for the NS component [54]. This ratio is important for several reasons, as higher amplification ratios might indicate higher flexibility in the NS direction and more pronounced oscillations during the seismic event. The amplification ratio is a crucial parameter in earthquake engineering, enabling the assessment of a building's seismic performance and ensuring its safety during earthquakes. The PGV/PGA (PFV/PFA) ratio, shown in Table 1, is a measure used in earthquake engineering to describe the relationship between peak ground velocity (PGV or PFV) and peak ground acceleration (PGA or PFA). This ratio can provide insights into the frequency content of ground motion and is an essential characteristic for emergency preparedness and urban planning [55]. A higher PGV/PGA ratio indicates ground motion with more low-frequency content (SGL1), which can be more harmful to specific structures (skyscrapers, flexible bridges, mats, etc.). A high PGV/PGA ratio may lead to design strategies that mitigate the effects of low-frequency ground motion. Usually, the analysis of displacement distribution in the horizontal plane (Figure 4a,b) is neglected or underestimated, but this makes the picture more apparent regarding how different parts of the ground move during an earthquake. \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline \multirow{2}{*}{**Location of the Record**} & \multirow{2}{*}{**Component**} & **PGA** & **PGV** & **PGD** & **PGV/PGA or** & **PFA (Sixth Floor) vs.** \\  & & **cm/s2** & **cm/s** & **cm** & **PFV/PFA** & **PGA (Basement)** \\ \hline \multirow{3}{*}{SGL1 Basement} & EW & 42.62 & 2.97 & 0.96 & 0.07 & \multirow{3}{*}{} \\  & NS & 30.26 & \(-\)4.76 & \(-\)1.35 & 0.16 & \\  & UD & 21.94 & 1.42 & \(-\)0.38 & 0.06 & \\ \hline \multirow{3}{*}{SGL2 Sixth floor} & EW & 87.15 & \(-\)7.77 & \(-\)1.57 & 0.09 & \multirow{3}{*}{} \\  & NS & \(-\)99.02 & 6.45 & \(-\)1.57 & 0.07 & \\ \cline{1-1}  & UD & 46.21 & 1.98 & 0.55 & 0.04 & \\ \hline \multirow{3}{*}{SGL1 vs. SGL2} & EW & & & & & 2.04 \\ \cline{1-1}  & NS & & & & 3.27 \\ \cline{1-1}  & UD & & & & 2.11 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The main parameters of the records in the basement and on the sixth floor. The EW PGV/PGA ratio indicates higher frequency content. Values < 0.1 suggest short-period ground motion, which can be potentially damaging for stiff structures. The NS component in the base shows a more intermediate period character, which is more demanding for mid-rise structures. The vertical content remains short-term; it has less influence on large deformations but is critical for detailing. Codes such as FEMA P-1050 [56] suggest that PGV/PGA < 0.2 aligns with pulse-type or stiff-soil profiles, while values greater than 0.3 reflect long-period ground motion that is more damaging to flexible structures. Seismic ground motions near a fault, as is the case with the 2012 Pernik earthquake, are often characterized by intense velocity and displacement pulses with relatively long periods, which clearly distinguish them from typical distant-source ground motions.