**2. Literature survey**

This section mainly focuses on a survey regarding four different aspects. First, high seismicity in Turkey, particularly in the Marmara region, is briefly explained. Secondly, two initiatives functioning seismic risk mitigation measures, earthquake early warning, and structural health monitoring systems in the region, are introduced. Finally, next generation attenuation (NGA) models are discussed.

## **2.1 Seismicity in Marmara region**

Turkey is one of Europe's most seismically active countries, and it has been struck by multiple catastrophic earthquakes throughout its history. These earthquakes (*Mw* 6.7 1992 Erzurum, *Mw* 6.1 1995 Dinar, *Mw* 6.3 1998 Adana-Ceyhan, *Mw* 7.6 1999 Kocaeli, *Mw* 7.2 1999 Düzce, *Mw* 6.4 2003 Bingöl, *Mw* 7.2 2011 Van, *Mw* 7.0 2020 İzmir, and *Mw* 6.7 2020 Elazığ) resulted in severe economic losses and physical damage, as well as a large number of fatalities. Ambraseys and Finkel [27] documented 32 devastating earthquakes that hit the larger Marmara Sea region between the fourth and nineteenth centuries, affecting Istanbul. Following the devastation caused by the two major earthquakes that struck the Marmara region in 1999, governmental, nongovernmental, and academic organizations in Turkey have acknowledged the need for extensive response planning based on rigorous risk analyses of likely seismic hazards in Turkey and Istanbul in particular [5].

Le Pichon, Şengör [28] examined an earthquake scenario and provided a projection for two active fault lines located 20–30 kilometers southwest and south of central Istanbul: (1) the Central Marmara Basin (CMB) and (2) the North Boundary Fault (NBF), respectively. Some researchers found that within the next 30 years, the likelihood of an earthquake of magnitude seven or greater occurring in the Marmara Sea is around 65% Parsons [29, 30]. Considering more than two decades have passed after two severe earthquakes, a possible Istanbul earthquake may be in the near future.

Ansal, Akinci [31] provided significant results on earthquake loss assessment in Istanbul. Based on the 1999 Kocaeli earthquake investigation, they discovered critical parameters for the seismic ground motion simulation. In terms of the loss estimate, the CMB fault section is more critical due to the higher seismic excitation intensity it may cause. Okay, Kaşlılar-Özcan [32] indicated that the CMB segment has not raptured since 1766 and poses an urgent threat to the region. Ergintav, Reilinger [33] determined that the Princes' Island region of the Marmara Sea is most likely to cause the next Mw > 7 earthquakes along the NAFZ. Recent studies were conducted by Woessner, Laurentiu [34] to construct a reference hazard model for Europe. They reported that the mean peak ground acceleration (PGA) with a 10% probability of exceedance in 50 years provides the highest seismic hazard estimate (PGA ≥ 0.25 g) along the NAFZ, with values up to 0.75 g in the northern Aegean and the Marmara Sea.
