The Anatolian microplate represents a key site for studies that will focus on earthquake mechanisms, plate-scale interaction of seismicity, and complex deformation processes at transform plate boundaries. At its northern plate margin, the North Anatolian Fault Zone (NAFZ) represents one of the most prominent continental transforms on earth, forming a 1600 km long plate boundary with substantial earthquake risk. Large parts of the Marmara Sea south of the megacity of Istanbul represent a seismic gap along a ≥ 100 km long fault segment. The integrated PBO concentrates on this fault segment by means of the installation of a high-resolution borehole seismic array around the Eastern Sea of Marmara/NW Turkey. We expect to provide new insights into physical processes acting prior and potentially also during and after a large (M>7) earthquake and to refine and calibrate ground shaking models and perform near real time hazard assessments for the megacity of Istanbul to contribute to Istanbul’s early warning system.