Earthquake Hazard in Urban Areas of Bursa Province: Paleosismological Properties of the Ulubat, Bursa and İnegöl Active Faults
Abstract: 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 Türkiye`s strategic economic centers with a dense population and industrial infrastructure, Bursa requires a holistic seismicrisk 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 Nilüfer Region of Bursa. Trench investigations conducted in Bursa citycentre 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 İnegöl Fault indicate that the İnegöl Fault hasproduced 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 İnegöl faults to rupture simultaneously either in close succession, possibly triggering one another. Thus, the surface rupture caused by the1855 Bursa earthquake is evaluated to have potentially triggered stress accumulation along the İnegöl Fault. Thissituation reveals a high probability of a surface-rupturing earthquake (M=6.2-6.9) occurring at any time on the İnegöl Fault, after 2500 years of seismic silence. Overall, these findings underscore the critical role of the faults in Bursa and its surroundings within the regionalseismicity. In particular, the potential for sequential ruptures along the Bursa and İnegöl 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.