Environmental Management Hazards

Environmental Management Hazards

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
َAzra Sharifi 1
Arezou Dorostian 1
Mehdi Zare 2
Majid Mahood 2
Soheila Bouzari 3
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
Urmia؛ Seismicity
parameters؛ Gutenberg–Richter relationship؛ Seismotectonics؛ Seismic hazard assessment
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Environmental Management Hazards
Volume 13, Issue 1
Spring 2026
Pages 53-66