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چکیده
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Northwest Iran, which is situated in the seismically active Alpine-Himalayan belt, is recognized as a high-seismicity region due to the convergence between the Arabian and Eurasian tectonic plates. The present study provides a detailed analysis of an earthquake catalog between the years 2006 and 2024, aiming to investigate the spatio-temporal patterns of seismicity in the area. We evaluated a number of parameters such as the temporal and spatial variation of Magnitude of Completeness (MC), Fractal Dimension (DC-value), Gutenberg-Richter b-value (with respect to overall, depth-dependent, spatial, and temporal variations), and seismic quiescence Z-values distribution. The distribution of seismic activity is clustered with a fractal dimension of 1.75 ± 0.05. Further, the b-value is estimated at 0.76 ± 0.01, suggesting occurrence of large magnitude earthquakes. Spatial variations in the b-value show high values (1-1.3) close to the North Tabriz Fault and close to volcanic regions, with low values (0.4–0.6) in the western region of the area, which is consistent with the spatial pattern of DC and Z values, suggesting significant clustering along significant tectonic lines. Temporal variation in the b-value shows fluctuation, including co-seismic drops and potential precursory rises associated with large seismic events. The variation of b-value in the vicinity of Ahar-Varzeghan earthquake doublets aligns with the identified mechanisms of strike-slip and thrust faulting. The comprehensive findings enhance our understanding of the complicated seismotectonic background of Northwest Iran, highlighting a varied stress field and clustering characteristics that are important for the assessment of regional seismic hazards.
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