Environmental Management Hazards 2423-415X 13 1 2026 07 11 Spatial and temporal variation in b-value and z-value of magnitude-frequency earthquake distribution in Urmia region, North-West part of Iran Spatial and temporal variation in b-value and z-value of magnitude-frequency earthquake distribution in Urmia region, North-West part of Iran 53 66 107803 10.22059/jhsci.2026.416318.943 FA َAzra Sharifi Department of Geophysics, NT.C., Islamic Azad University, Tehran, Iran 0009-0001-3114-6665 Arezou Dorostian Department of Geophysics, NT.C., Islamic Azad University, Tehran, Iran 0000-0002-2106-7752 Mehdi Zare International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran 0000-0003-1036-4265 Majid Mahood International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran Soheila Bouzari Department of Geology, NT.C., Islamic Azad University, Tehran, Iran Journal Article 2026 06 10 This study aims to quantify seismicity parameters and characterize the spatiotemporal evolution of earthquake activity in Northwestern Iran (35°–39° N, 44°–47° E), a region of significant seismotectonic importance due to its active fault systems. Utilizing the Iranian Seismological Center (IRSC) catalog for the period 2006–2025, we determined the magnitude of completeness (Mc​=1.9) and calculated the b-value using the Gutenberg–Richter relationship. Furthermore, Z-value statistical mapping was employed to identify anomalies in seismic activity rates. The analysis yielded a b-value of 0.79±0.01, suggesting a relatively higher probability of large-magnitude seismic events in the region. Spatiotemporal assessment revealed that sectors surrounding Lake Urmia, particularly the western and southern margins, exhibit positive Z-values, indicating seismic quiescence and potential stress accumulation. Conversely, regions intersecting major fault systems, such as the Tabriz and Sofian faults, demonstrate negative Z-values, reflecting persistent seismic activity. Additionally, the analysis of seismic energy release from 2006 to January 2025 identifies the 2012 East Azerbaijan earthquake (Mw=6.5) as the most significant seismic event of this period. The observed seismic quiescence surrounding Lake Urmia, coupled with localized stress accumulation indicators, highlights a heightened potential for future seismic ruptures. These findings provide critical evidence for refining seismic hazard assessments and developing more accurate regional earthquake forecasting models in Northwestern Iran. This study aims to quantify seismicity parameters and characterize the spatiotemporal evolution of earthquake activity in Northwestern Iran (35°–39° N, 44°–47° E), a region of significant seismotectonic importance due to its active fault systems. Utilizing the Iranian Seismological Center (IRSC) catalog for the period 2006–2025, we determined the magnitude of completeness (Mc​=1.9) and calculated the b-value using the Gutenberg–Richter relationship. Furthermore, Z-value statistical mapping was employed to identify anomalies in seismic activity rates. The analysis yielded a b-value of 0.79±0.01, suggesting a relatively higher probability of large-magnitude seismic events in the region. Spatiotemporal assessment revealed that sectors surrounding Lake Urmia, particularly the western and southern margins, exhibit positive Z-values, indicating seismic quiescence and potential stress accumulation. Conversely, regions intersecting major fault systems, such as the Tabriz and Sofian faults, demonstrate negative Z-values, reflecting persistent seismic activity. Additionally, the analysis of seismic energy release from 2006 to January 2025 identifies the 2012 East Azerbaijan earthquake (Mw=6.5) as the most significant seismic event of this period. The observed seismic quiescence surrounding Lake Urmia, coupled with localized stress accumulation indicators, highlights a heightened potential for future seismic ruptures. These findings provide critical evidence for refining seismic hazard assessments and developing more accurate regional earthquake forecasting models in Northwestern Iran. https://jhsci.ut.ac.ir/article_107803_d0c9456ec73683c475c40338318f704e.pdf