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 Phd Student in Geophysics (seismological orientation) of Islamic Azad University of North Tehran, Tehran, Iran

2 Department of Geophysics, Division of Seismology, Islamic Azad University, North Tehran Branch, Tehran, Iran

3 International Institute of Earthquake Engineering and Seismology, 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

  • Aghanabati, S. A. (2004). Geology of Iran. Geological Survey of Iran, 587 p. (Persian).
  • Aki, K. (1965). Maximum likelihood estimates of b in the formula logN = a − bM and its confidence limits. Bulletin of the Earthquake Research Institute, University of Tokyo, 43, 237–239.
  • Alavi, M. (1991). Sedimentary and structural characteristics of the Paleo‑Tethys remnants in northeastern Iran. Geological Society of America Bulletin, 103(8), 983–992.
  • Berberian, F., & Berberian, M. (1981). Tectono‑plutonic episodes in Iran. In H. K. Gupta & F. M. Delany (Eds.), Zagros–Hindu Kush–Himalaya Geodynamic Evolution (pp. 5–32). American Geophysical Union.
  • Berberian, M. (1974). Structural history of the Southern Lut Zone (Northern Highlands of Jaz Murian Depression, Baluchestan): A preliminary field note. Internal Report No. 21, Geological Survey of Iran, 21 p.
  • Berberian, M., & Yeats, R. S. (1999). Patterns of historical earthquake rupture in the Iranian Plateau. Bulletin of the Seismological Society of America, 89(1), 120–139.
  • Copley, A., & Jackson, J. (2006). Active tectonics of the Turkish–Iranian plateau. Tectonics, 25(6).
  • Eftekhar‑Nezhad, J. (1975). Brief history and structural development of Azerbaijan. Geological Survey of Iran (Internal Report), 8 p.
  • Eftekhar‑Nezhad, J., Aghanabati, A., Hamzehpour, B., & Baroyant, V. (1976). Geological map of Kashmar, scale 1:250,000. Geological Survey of Iran.
  • ESRI (Environmental Systems Research Institute) (2022). ArcGIS Pro (Version 3.0). Redlands, CA: Environmental Systems Research Institute.
  • Gutenberg, B., Richter, C. F., & Benioff, H. (1949). Earthquake study in southern California, 1948. Eos, Transactions American Geophysical Union, 30(4), 595–598.
  • Hanks, T. C., and Kanamori, H. (1979). A moment magnitude scale. Journal of Geophysical Research, 84(B5), 2348–2350.
  • Hosseini, H., Pakzad, M., & Naserieh, S. (2019). Iranian regional centroid moment tensor catalog: Solutions for 2012–2017. Physics of the Earth and Planetary Interiors, 286, 29–41.
  • Karimiparidari, S., Zaré, M., Memarian, H., & Kijko, A. (2013). Iranian earthquakes: A uniform catalog with moment magnitudes. Journal of Seismology, 17(3), 897–911.
  • Keller, E. A., & Pinter, N. (2002). Active Tectonics: Earthquakes, Uplift, and Landscape. Prentice Hall.
  • Kelt, K., & Shahrabi, M. (1986). Holocene sedimentology of hypersaline Lake Urmia, northwestern Iran. Palaeogeography, Palaeoclimatology, Palaeoecology, 54(1–4), 105–130.
  • Lay, T., & Wallace, T. C. (1995). Modern Global Seismology. Academic Press.
  • MathWorks (2022). MATLAB version 9.13.0 (R2022b). Natick, Massachusetts: The MathWorks Inc.
  • Mirzaei, N., Mengtan, G., & Yuntai, C. (1998). Seismic source regionalization for seismic zoning of Iran: Major seismotectonic provinces. Journal of Earthquake Prediction Research, 7, 465–495.
  • Rahimi, H., & Rastgoo, M. (2022). Application of NDSHA at regional and local scale in Iran. In A. A. Gholizadeh & M. Zare (Eds.), Earthquakes and Sustainable Infrastructure (pp. 583–600). Elsevier.
  • Schorlemmer, D., Wiemer, S., & Wyss, M. (2004). Earthquake statistics at Parkfield: 1. Stationarity of b values. Journal of Geophysical Research: Solid Earth, 109(B12), B12307
  • Seyed‑Emami, K., Schairer, G., & Bolourchi, M. H. (1985). Ammoniten aus der unteren Dalichy‑Formation (oberes Bajocium bis unteres Bathonium) der Umgebung von Abe‑Garm (Avaj, NW‑Zentraliran). Zitteliana, 12, 57–85.
  • Shahrabi, M. (1981). Holocene lacustrine facies and environment of hypersaline Lake Urmia, NW Iran. Unpublished diploma thesis, ETH Zurich, Switzerland, 75 p.
  • Shahrabi, M. (1994). Description of the Urumieh geological map (scale 1:250,000). Geological Survey of Iran, Report No. B3, 90 p.
  • Sharabi, M. (1990). Geological map of Gorgan, scale 1:250,000. Geological Survey of Iran.
  • Tavakoli, B., & Ghafory‑Ashtiany, M. (1999). Seismic hazard assessment of Iran. Annals of Geophysics, 42(6).
  • Tavakoli, F., & Ghafory‑Ashtiany, M. (1999). Seismic hazard assessment of Iran. Annali di Geofisica, 42, 1013–1022.
  • Verstappen, H. T. (1983). Applied Geomorphology: Geomorphological Surveys for Environmental Development. Elsevier.
  • Walker, B., Holling, C. S., Carpenter, S. R., & Kinzig, A. (2004). Resilience, adaptability and transformability in social‑ecological systems. Ecology and Society, 9(2).
  • Wiemer, S., & Wyss, M. (1994). Seismic quiescence before the Landers (M7.5) and Big Bear (M6.5) 1992 earthquakes. Bulletin of the Seismological Society of America, 84, 900–916.
  • Wiemer, S., & Wyss, M. (1997). Mapping the frequency‑magnitude distribution in asperities: An improved technique to calculate recurrence times. Journal of Geophysical Research: Solid Earth, 102(B7), 15115–15128.
  • Wiemer, S. (2001). A software package to analyze seismicity: ZMAP. Seismological Research Letters, 72(3), 373–382.
  • Zare, M., & Shahpasand Zade, M. (1995). Elementary investigation of seismicity, seismotectonics and seismic risk of East Azerbaijan. International Institute of Seismology and Earthquake Engineering, Tehran.
Environmental Management Hazards
Volume 13, Issue 1
April 2026
Pages 53-66

Files

Share

How to cite

Statistics