## 5 Analysis of the Impact of Ground Motion Parameters on Seismic Response
As it is shown, PGA has a limited correlation with the IDR, as it does not account for the duration of shaking and longer-term structural deformations, where peak PGA values alone do not provide a complete picture of structural response, as the IDR is influenced by frequency content and structural properties (damping and stiffness). PGV is considered a better indicator of structural damage compared to PGA, as it reflects the energy transmitted to the structure and its ability to absorb deformations. High PGV values (>50 cm/s) are obviously frequently associated with significant interstory drifts, even when PGA values are not exceptionally high. The IDR has a stronger correlation with PGV than with PGA, as PGV accounts for the duration and frequency content of the earthquake ground motion. PGD values often correlated with higher IDR values, suggesting that displacement plays a crucial role in structural performance assessment; however, for the Zagreb scenario results showed low correlation. Figure 10 presents the relationship between SED (specific energy density) and Ia (Arias intensity) with the IDRs for two different scenarios (ZG and DU locations):  
* SED vs. IDR: Significant peaks in SED values are observed (e.g., ZG11 and DU6), which coincide with increased IDR values. Higher SED values tend to result in a higher IDR, reinforcing the relationship between the energy absorbed by the structure and its deformation. * Ia vs. IDR: Higher Ia values, particularly in ZG10 and DU6, align well with increased IDR values, the trend of Ia vs. IDR indicates that areas with more intense ground shaking correlate with greater structural deformations. Higher SED values are typically associated with greater structural damage, with an indication that SED has a strong correlation (0.7-0.9) with the IDR, making it a critical parameter for damage assessment. Ia values have also shown a strong correlation with the IDR, and are particularly useful for predicting long-duration shaking effects. Spectrum-based metrics (Figure 11): ASI (Arias spectral intensity) and HI (Housner Intensity) with IDRs showed the following relations:  
* ASI vs. IDR: ASI values generally increase with IDR, showing that higher spectral intensity levels are associated with greater structural deformations. In some cases,  
Figure 9: Comparison of traditional ground motion metrics with IDRs for both scenarios. relatively low ASI values generated a moderate IDR, suggesting that correlation is moderate. * HI vs. IDR: a high HI tends to exhibit substantial interstory drift, indicating its relevance in structural performance assessment. ASI represents the cumulative energy transmitted to a structure based on spectral content, accounting for acceleration over time. Higher ASI values correlate strongly with the IDR, indicating that structures subjected to high spectral intensities are prone to larger drifts. HI measures spectral velocity over a broad frequency range and is useful for assessing the potential for structural damage. HI values show a strong correlation with the IDR, particularly for mid-rise and high-rise buildings with longer fundamental periods. Studies indicate that HI values above 1000 cm are typically associated with significant interstory drifts exceeding 2%, which can lead to structural compromise. The analysis of duration-based ground motion metrics with IDRs (Figure 12) presents the relationship between UD (Uniform Duration) and SD (Significant Duration) with the following observations:  
* UD vs. IDR: higher UD values tend to indicate longer shaking durations, which can lead to cumulative structural drift, correlating with an increased IDR. * SD vs. IDR: SD, which measures the duration during which significant seismic energy is transmitted to the structure, exhibits noticeable peaks, especially in the DU scenario. Figure 11: Comparison of spectrum-based ground motion metrics with IDRs for both scenarios. Figure 10: Comparison of energy-based ground motion metrics with IDRs for both scenarios.