Earthquake Hazard in Urban Areas of Bursa Province: Paleosismological Properties of the Ulubat, Bursa and İnegöl Active Faults

This study provides a detailed mapping of active fault segments in Bursa and its surrounding regions, along with a comprehensive analysis of seismic behavior derived from paleoseismological data. As one of T & uuml;rkiyes' strategic economic centers with a dense population and industrial infrastructure, Bursa requires a holistic seismic risk assessment for effective disaster preparedness and mitigation. Paleoseismological analyses of the eastern segment of the Ulubat Fault indicate that it has been in a seismic quiescence period for approximately 1855 years. This prolonged period of inactivity highlights the potential for a large earthquake in the future around the Nil & uuml;fer Region of Bursa. Trench investigations conducted in Bursa city-centre reveal that the Bursa Fault has produced at least six surface ruptures over the past 12000 years, recurring approximately every 2000 years. Additionally, trench studies on the & Idot;neg & ouml;l Fault indicate that the & Idot;neg & ouml;l Fault has produced at least five surface ruptures over the last 12000 years, with the most recent major earthquake occurring more than 2500 years ago. Obtained results emphasize the potential for the Bursa and & Idot;neg & ouml;l faults to rupture simultaneously or in close succession, possibly triggering one another. Thus, the surface rupture caused by the 1855 Bursa earthquake is evaluated to have potentially triggered stress accumulation along the & Idot;neg & ouml;l Fault. This situation reveals a high probability of a surface-rupturing earthquake (M=6.2-6.9) occurring at any time on the & Idot;neg & ouml;l Fault, after 2500 years of seismic silence. Overall, these findings underscore the critical role of the faults in Bursa and its surroundings within the regional seismicity. In particular, the potential for sequential ruptures along the Bursa and & Idot;neg & ouml;l faults presents a significant earthquake hazard. This comprehensive analysis contributes to a deeper understanding of the seismotectonic dynamics of the region, providing valuable insights for seismic hazard assessment and risk mitigation efforts.