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Abstract

The East Anatolian Fault Zone (EAFZ) represents plate boundary extending currently over ~500 km between the Arabian and Anatolian plates. Relative motion of the plates occurs with slip rates ranging from 6 to 10 mm/yr and has resulted in destructive earthquakes in Eastern Turkey as documented by historical records. In this study, we investigate the seismic activity of several fault segments of the EAFZ as well as their interaction. We combine data from all available regional seismic stations operated by the Kandilli Observatory Earthquake Research Institute and the Directorate of Disaster Affairs to achieve the best possible azimuthal coverage for the target region. We optimize a reference 1-D velocity model using a grid-search approach and re-locate hypocenters using the Double- Difference earthquake relocation technique. The refined hypocenter map provides insights into the kinematics and internal deformation within the fault zone down to a resolution ranging typically between 100-200 m. The distribution of hypocenters suggests that the EAFZ is characterized by NE-SW and EW oriented sub-segments that slightly deviate from the overall trend of the fault zone. The main fault is surrounded by sub-parallel aligned hypocenters possibly representing subsidiary faults. Structural variation along the EAFZ significantly affects faulting mechanisms along the fault that indicate predominantly left-lateral strike slip which turns into normal/thrust faulting depending on the strike of local fault segments. Spatiotemporal evolution of hypocenters indicates a systematic migration of micro- and moderate-sized earthquakes within several days documenting progressive interaction between the main fault and subsidiary faults.