Seismic hazard and risk analyses of historical masonry structures in Kocaeli, Türkiye

Protection of masonry structures is among the most important building groups around the world. Generally constructed of heavy materials such as stone and brick, these structures are highly seismically vulnerable. In large earthquakes, masonry structures that have not received adequate engineering services are usually heavily damaged or destroyed. To prevent damage to these structures, seismic hazard and risk analyses must first be conducted correctly. This study investigates the seismic hazards and risk distributions of historical masonry structures in Kocaeli, Türkiye. As a preliminary step, information and document collection studies on historical masonry structures were conducted in Kocaeli, Türkiye. Then, a detailed building inventory data set was prepared. Following that, a probabilistic seismic hazard assessment for the investigation area was conducted considering the different attenuation relationships. In the seismic hazard analyses, the hazard maps, hazard curves and response spectra were prepared based on the inventory data set at select reference points. After that, the seismic risk analyses were conducted to determine the structure distribution based on damage levels for the structures in the data set considering different fragility curves. Accordingly, historical masonry structures in Kocaeli province close to the North Anatolian Fault (NAF) Line have high hazard curves and spectrum values, whereas structures on the Black Sea coast have low values. According to the hazard maps obtained as a result of the analyses, Kartepe, Darica, Gölcük, and Başiskele districts have a high estimated hazard distribution, while Kandira has a lower estimated hazard distribution. Further, when the risk assessment is carried out by looking at the distribution of building groups based on damage levels, it was determined that towers, aqueducts, residential structures, and dome structures are the highest priority risk structures, respectively.