Scientists conducted the GONAF project to drill and install a high‑resolution borehole seismic observatory along the North Anatolian Fault Zone near Istanbul, Turkey. They drilled shallow vertical boreholes up to 500 meters deep around the eastern Sea of Marmara to detect tiny quakes and locate them more precisely. The main goal is to study what happens before, during and after a big M>7 quake on the Princes Islands segment of the fault and to learn how seismic waves travel through rock during such a rupture by recording waves from several spots. In addition to ICDP-funded boreholes, four shallower holes were drilled to house strainmeters that measure ground movement. In total about 2.1 kilometers of drilling was done at multiple sites. By collecting data over time, scientists hope to better understand earthquake physics, improve hazard assessments, and help communities prepare for future earthquakes.