## 2 Ground Motion Record Selection
### Code-Based Record Selection  
Modern seismic codes mainly use the spectral matching-based GM selection [13; 14; 15] and provide simplified and similar guidelines for the selection and scaling of GMs. Differences are mainly due to the number of GM records and period ranges for compatibility with the mean spectrum of selected GMs and the target spectrum. For example, EC8 recommends using seven GM records to evaluate the mean structural response, while both the TBEC and ASCE 7-16 suggest using eleven GM records. The period range where compatibility between the mean spectrum and target spectrum must be ensured should be 0.27-2.07, 0.27-2.07, and 0.27-1.5T for EC8, ASCE 7-16, and the TBEC, respectively. The other difference is about the limit of the ratio of the mean spectrum to the target spectrum. The lower limits of this ratio are 0.90, 0.90, and 1.00 for EC8, ASCE 7-16, and the TBEC, respectively. Neither the compatibility of the individual spectrum in the sets nor the upper limit for the mean-spectrum-to-target-spectrum ratio is controlled in these codes. It is also worth noting that the choice of the period interval for matching may vary depending on the type of study. For building a specific analysis, the assumptions provided in these codes may be viable. On the other hand, the interval for matching can be larger for large-scale analysis. It should be also noted that uni-directional and bi-directional analysis, which also affect the GM selection, are recommended for two- and three-dimensional structural models. For uni-directional analysis, one of two horizontal components for the critical axis of the structure is considered. The combined spectrum refers to the use of both horizontal GM component pairs for three-dimensional analysis. Generally, three types of combined spectra are employed: (a) the square root of the sum of squares (SRSS), (b) the geometric mean, and (c) period-dependent rotated spectra, which may include minimum (0 th percentile), median (50 th percentile), or maximum (100 th percentile) directional values. The SRSS combined spectrum is used for three-dimensional analysis of structures according to the TBEC and EC8. In this study, TBEC and EC8 target spectra were considered for GM selection in the orientation of horizontal and vertical directions. The parameters used to derive the target spectrum according to the TBEC and EC8 are given in Table 1. To assess the ability of the solution model, different local soil classes (i.e., Soil B and C for EC8 and Soil ZC and ZD for the TBEC) were also considered. It can be seen in the table that the \(V_{s,30}\) values of distinct soil classes are different for both the seismic codes. The horizontal and vertical target spectra of the EC8 and TBEC are also given in Figure 1. The figure clearly illustrates that the capability of the solution model will be tested under a variety of target spectra for both seismic codes. In this study, GM selection was performed considering real GM records obtained by recent earthquakes. These earthquakes have different spectral characteristics, such as earthquake magnitude, local soil types, the distance, etc. For this purpose, the Pacific Earthquake Engineering Research (PEER) database, which consists of thousands of records with different features, was used and three components (two horizontal (X and Y) and one vertical (Z)) of GM records were downloaded from it [60]. While downloading the GM records, the magnitude (\(M_{w}\)), epicentral distance (\(R\)), and \(V_{s,30}\) were considered. GM records with an \(M_{w}\) value greater than 5.5 and a distance between 15 km and 100 km were downloaded. Considering the recently proposed \(M_{\text{mg}}\) scale, which uses body-wave magnitude instead of surface waves [61], \(M_{\text{mg}}\) values of the downloaded records are between 5.19 and 7.53 for Soil B-ZC and between 5.19 and 7.83 for Soil C-ZD. As a result, 467 and 498 GM records have been downloaded for Soil B-ZC and Soil C-ZD local soil classes, respectively.