3rd TAGRA

The Bolu–Düzce region in northwestern Türkiye is characterized by intense tectonic and seismic activity associated with the North Anatolian Fault Zone (NAFZ). This study investigates the relationship between seismicity, active fault systems, and regional magnetic structure through an integrated analysis of earthquake and magnetic data. Seismicity is evaluated using M > 3.0 earthquakes recorded between 1900 and 2026 from the Kandilli Observatory and Earthquake Research Institute catalogue. Earthquake epicenters are mapped according to focal depth and compared with the regional active fault pattern. The magnetic structure is investigated using the EMAG2-v3 magnetic anomaly dataset, which was processed using magnetic data enhancement and spectral analysis techniques to characterize regional magnetic variations and estimate magnetic source depths. The results show that seismicity is predominantly concentrated along and around the principal branches of the NAFZ. Magnetic anomalies exhibit distinct spatial variations across the study area, while enhanced anomaly patterns delineate structural boundaries and lineaments that locally correspond to active fault traces and zones of concentrated seismicity. Variations in magnetic source depths also indicate lateral changes in the subsurface magnetic structure. The integrated interpretation of seismic and magnetic data provides complementary constraints on the tectonic architecture of the Bolu–Düzce region and contributes to a better understanding of active deformation along the western NAFZ.