## 3 Results and Discussion
### Determination of Design Horizontal Response Spectra and Site Coefficient
#### 3.3.1 Design Horizontal Response Spectra  
In this study, results of spectral acceleration were presented based on far-field, near-field, and a combination of far-field and near-field. Then, DHRS were proposed based on the average and envelope for soil types D and E. Far-field seismic events were represented by F1-F3, while near-field seismic events were represented by N1-N3. Results of the  
Figure 12: Map of the soil amplification factor for the 200-year return period. average spectral acceleration under far-field seismic events obtained from one-dimensional nonlinear GRA for sites D1-D4 under far-field, near-field, and a combination, are presented in Figure 13. This phase proposes DHRSa for soil types D and E. However, only results for soil type D are discussed in this section to help in understanding the process of proposing DHRSa. Referring to Figure 13, it can be seen that three out of four sites in this study showed a peak value of approximately 0.14 g. Site D3 showed a peak value at 0.2 s while at site D1, the peak value occurred between 1 and 2 s. At sites D2 and D4, the peak values occurred between 2 and 3 s. In far-field seismic events, highest Sa values were predicted for F3; in all events, D2 showed the lowest value. The average and envelope for each site were then used in predicting Sa for soil type D under far-field seismic events, as shown in Figure 13. The highest peak for the average was 0.90 g, which occurred at 1.35 s while the highest value for the envelope was 0.146 g at 1.3 s.  
Figure 13,\(e\) show results on DHRSa under near-field seismic events for soil types D and E. Three seismic events were used in the analysis of the ground response of the selected sites in the Malay Basin. In Figure 13, the peak for D3 was slightly higher than D1 while D4. The highest value predicted at D3 was almost  
Figure 13: Average spectral acceleration for soil type D.  
0.35 g. The lowest value for the peak was found at site D4, which was close to 0.25 g. To avoid underestimating or overestimating, the average of all seismic events along with the envelope of HRSa for soil type D, are plotted in Figure 13e. After looking at the Sa based on the single application of either far-field or near-field, results of Sa for each site were combined and the average (based on soil type) was plotted. The plotting of the average soil type D under the combination of far-field and near-field is shown in Figure 13c. The highest peak occurred at D1, followed by D3, D4, and D2. D1 and D3 shared a slightly different pattern of Sa over a period. The average and envelope of Sa for D1-D4 are plotted in Figure 13f. The highest value for the average was 0.17 g and 0.23 g for the envelope of soil type D. The peak motion at sites D1 until D4 occurred around 1 s.  
Results for the proposed DHRSa along with Sa proposed by ISO 19902 were compiled (Figure 14a,b) based on soil type. From Figure 14a, the proposed DHRSa for soil type D were higher compared to DHRSa proposed in ISO 19902, except for Dave far-field which was slightly higher by 0.004 g. In terms of region, for constant acceleration in DHRSa, the proposed DHRSa obtained longer periods compared to ISO. Dave near-field recorded the same highest Sa value as the Denv combination but with a shorter period of constant acceleration. Looking into the seismic scenario (far-field, near-field, and the combination), the Dave far-field had the lowest value while the Denv near-field produced the largest value. In Figure 14b, it can be seen that the average and envelope of the proposed DHRSa were also higher compared to ISO. The longest constant acceleration period occurred in the far-field, followed by near-field and the combination. A comparison in the constant acceleration region resulted in a shorter period for ISO compared to the proposed DHRSa. In this section, DHRSa under a 5% damping ratio for the 1000-year return period and site coefficient values for the Malay Basin are proposed.