<p>This study investigates the seismic demands of the 23 April 2025 Silivri earthquake (M_w = 6.2) and damage distribution across 38,049 inspected buildings in İstanbul. Although the building stock is characterized by poor structural quality, no significant damage was reported, even at settlements with a PGA of 0.21&#xa0;g. Post-earthquake damage assessments were compared with pre-estimated seismic risk distributions, providing a rare opportunity to evaluate predictive models against real outcomes. A critical discussion of the soil amplification factors prescribed in the 2018 Turkish Seismic Design Code is conducted using the ground-motion amplitudes from approximately one million buildings. The performance of the substandard building stock in İstanbul is further evaluated by integrating observed damage distributions with structural characteristics and pre-earthquake seismic risk estimations for nearly 25,000 reinforced concrete buildings. A strong agreement is observed between pre-earthquake risk levels and post-earthquake damage observations, revealing neighborhood-scale damage hotspots and providing validation for large-scale seismic risk assessments. Comparative analyses demonstrate that earthquakes with significantly higher PGA values may not necessarily result in widespread damage, highlighting the importance of spectral demand measures and ground-motion duration. The detailed numerical analyses of a representative substandard building that survived the earthquake without structural damage help explain the possible reasons why this substandard building experienced only limited damage during the event. The results suggest that, for the representative building considered in this study, infill walls limited the damage by reducing the displacement demand under the relatively short-duration Silivri ground motion. In contrast, the same building type reached collapse when subjected to a longer-duration ground-motion record with a comparable PGA from the 2023 Kahramanmaraş earthquake.</p>