Characteristics of the dynamic response of the Sultan Ahmet Mosque (Istanbul) to earthquakes

Abstract

The 400-year-old Sultan Ahmet Mosque is located southwest of the ancient hippodrome in Istanbul's historical peninsula. This historic structure, which has survived from the Ottoman period, experienced many damaging earthquakes in the North Anatolian Fault, especially in the fault segments within the Marmara Sea, since its construction was completed in 1617. The mosque is prominent as a cultural heritage element in the city. Therefore, its primary structural system has been monitoring since 2012. The Structural Health Monitoring system deployed in the mosque consists of ten triaxial (two horizontal, one vertical) accelerometers functioning at a sampling rate of 200 Hz. Sensors were installed as four at the main dome, four at the upper galleries of the pillars, one at the ground level, and the last one on the basement floor. Over two hundred recorded earthquakes between October 2012 and November 2020, whose magnitudes ranging from minor to strong, were processed and assessed through scripts coded on MatLab. Used criteria such as sensor completeness of an event and the signal-to-noise ratio of a recording initially reduced the number of earthquakes. Hence in this thesis, the final catalogue of 103 events was analysed in time- and frequency-domain after evaluating the catalogue statistically as functions of magnitude, distance, and azimuth. In the time domain, acceleration, velocity and displacement peaks were obtained and assessed individual- and group-based. Their various relations with earthquake magnitude and amplitude were also examined. In frequency domain analyses employing modal approaches, the dependence of dominant frequencies on time, temperature, earthquake magnitude, and ground motion amplitude was investigated. Particle motions and mode shapes for the selected largest-amplitude events were identified and depicted. Finally, the existence of soil-structure interaction and the rocking vibrations in the structure were investigated.