2022 Düzce, Türkiye earthquake: advances in the past 2 decades, lessons learned, and future projections

In the year 1999, two devastating earthquakes (M_w 7.4 Kocaeli earthquake in August and M_w 7.2 Düzce earthquake in November) occurred in Northwest Türkiye. These two earthquakes led to a very large number of casualties and building collapses. When the 1999 earthquakes occurred, most of the structures in the earthquake-impacted region were not designed according to modern seismic design codes. During the 25 years following those earthquakes, there have been significant advances in building construction in the light of earthquake engineering, including adequate seismic codes, new regulations, and effective code enforcement in the earthquake impacted region. These advances have been reflected in the construction of new structures in the region and the retrofitting of existing ones. As a result, 70–80% of the current building stock in Düzce was designed, constructed, or retrofitted after the 1999 earthquakes. Almost 23 years later, in 2022, an M_w 6.1 earthquake occurred in Düzce, with ground shaking close to the seismic design code life safety performance level. The 2022 earthquake provided a great opportunity to evaluate the effectiveness and consequences of the advances in earthquake engineering and the relevant policy-making and regulations. This paper provides a comparative overview of the 1999 and 2022 earthquakes that struck the city of Düzce in terms of hazard, vulnerability, and consequences. Furthermore, other key lessons learned from the 2022 Düzce earthquake are documented based on field reconnaissance and numerical simulations. The lessons learned are expected to provide useful guidance for the reconstruction efforts after the 2023 Kahramanmaraş Türkiye earthquake sequence or in similar efforts in other parts of the world.