Spatial and temporal variation in b-value and z-value of magnitude-frequency earthquake distribution in Urmia region, North-West part of Iran

Document Type : Applied Article

Authors

1 Department of Geophysics, NT.C., Islamic Azad University, Tehran, Iran

2 International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran

3 Department of Geology, NT.C., Islamic Azad University, Tehran, Iran

10.22059/jhsci.2026.416318.943

Abstract

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.

Keywords

References

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Environmental Management Hazards
Volume 13, Issue 1
April 2026
Pages 53-66

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