Comparison of Building Structure Performance with Variations in Concrete Quality and Earthquake Zones Resulting from Earthquake Loads Using Response Spectrum Method

South Sumatra is a region in Indonesia that rarely experiences earthquakes. However, this region is not completely safe and is often affected by earthquake tremors from surrounding areas. Therefore, structural design planning that resists earthquake loads is required. This study aims to analyze the response and performance of seven-story buildings in three regions—Palembang, Jakarta, and Palu—with varying concrete grades (K-300, K-400, and K-500) using the ETABS program. The analysis includes base shear, displacement, and inter-story drift, as well as a structural performance evaluation based on serviceability limits, ultimate limits, and performance levels in accordance with ATC-40. The structural response analysis shows that base shear in Jakarta (K-400) and Palu (K-500) increased by 51% and 79%, respectively, compared with Palembang (K-300). Meanwhile, the displacement and inter-story drift ratios in Jakarta and Palu, compared to Palembang, reached 31% and 39%, respectively. The results of the structural performance analysis show that, for all three areas, the inter-story drift and the maximum inter-story drift under the planned earthquake load remain below the permissible limits: less than 0.017 m for the serviceability limit and less than 0.080 m for the ultimate limit. Thus, all models meet the requirements of SNI 1726-2019 and are classified as safe. Based on ATC-40 criteria, the structure in Palembang (K-300) falls under the “Immediate Occupancy” category, while the structures in Jakarta (K-400) and Palu (K-500) fall under the “Damage Control” category, indicating good structural resistance to seismic loads.