Estimation of mechanism of earthquakes in active seismic areas around Tehran, Mashhad and Tabriz cities

Document Type : Research Article

Authors

1 MsC Student in Environment, Shahid Bahonar University of Kerman,Kerman,Iran

2 Professor in Geophysics, Shahid Bahonar University of Kerman Kerman,Iran

Abstract

In this study the data required to solve the mechanism of earthquakes were collected from a combination of waveform data from the Institute of Geophysics, the University of Tehran and the International Institute of Seismology and Earthquake Engineering. The first P-wave polarization method for the broadband, seismic stations were used to solve the earthquake mechanism. The location error of these earthquakes was about 5 km and the maximum rotation of the nodal plains in the mechanisms was considered 5 degrees. These mechanisms have been processed with the least error in the number of wrong polarizations for seismic mechanisms around the most populous cities of Tehran, Mashhad, and Tabriz. Based on the solution of seismic mechanism in this study, Mosha, north Tehran, Ipack, Garmsar and Ivanki faults, are considered to have the dominant mechanism of strike-slip right lateral with the small normal component, reverse, strike-slip left lateral, strike-slip with small reverse component and inverted mechanism, respectively. This research showed that the faults around Mashhad city like Bahler and Ashkabad left lateral strike slip with a small reverse component and reverse, respectively. The dominant mechanism of the 2017 Fariman aftershocks, is also inverse with the strike-slip right lateral component. Also, the resolved mechanisms of earthquakes around the historical city of Tabriz show that earthquakes with a dominant mechanism of strike-slip right lateral with a small reverse component are related to the North Tabriz fault. Other earthquakes, which are the aftershocks of the 2012 Ahar-Varzeqan doublete earthquakes, also have a strike-slip right lateral with a small reverse component. The 2012 Ahar-Varzeqan earthquakes also have a pure right lateral mechanism. The mechanism of some of these faults, which were studied in previous works (geologically or seismologically), are consistent with the mechanism solved in this study.

Keywords

©2025 The author(s). This is an open access article distributed under Creative Commons Attribution 4.0 International License (CC BY 4.0)

References

  •  Akasheh, B., & Berckhemer, H. )1984(. Focal Mechanisms of Earthquakes in Iran with Special Emphasis on Small Shocks in Tehran Region. Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen. 168(2-3), 244-255.
  •  https://doi.org/10.1127/njgpa/168/1984/244.
  • Ambraseys, M.M., & Melville, C.P. (1982). A History of Persian Earthquakes. Cambridge: Cambridge University Press.
  • Ashtari, Hatzfeld D., & Kamalian, N. (2005). Microseismicity in the Region of Tehran. Tectonophysics, 395(3-4), 193–208.
  •  https://doi.org/10.1016/j.tecto.2004.09.011.
  • Berberian,, (1976). Contribution to the Seismotectonics of Iran (Part II). Geological Survey of Iran, 39, 518.
  • Berberian, Yeats, R.S. (1999). Patterns of Historical Earthquake Rupture in the Iranian Plateau. Bulletin of the Seismological Society of America, 89(1), 120-139. https://doi.org/10.1785/BSSA0890010120.
  • Copley, A., Faridi, M., Ghorashi, M., Hollingsworth, J., Jackson, J., Nazari, H., Oveisi, B., & Talebian, M. (2013). The 2012 August 11 Ahar earthquakes: consequences for tectonics and earthquake hazard in the Turkish-Iranian Plateau. Geophysical Journal Journal, 196(1), 15-21. https://doi.org/10.1093/gji/ggt379.
  • De Martini, P.M., Hessami, K., Pantosti, D., D’ddezio, G., Alinaghi, H, Ghafori-Ashtiany, M. (1998). A Geologic Contribution of the Evaluation of the Seismic Potential of the Kahrizak Fault (Tehran, Iran). Tectonophysics, 287(1-4): 187–199. https://doi.org/10.1016/S0040-1951(98)80068-1.
  • Hessami, , Jamali, F. and Tabassi, H. (2003). Major active faults of Iran. International Institute of Earthquake Engineering and Seismology, Tehran.
  • Hollingsworth, J., Jackson, J., Alarcon, J., Boomer, J., Bolourchi, M.J. (2007). The 4th February 1997 Bojnourd (Garmkhan) Earthquake in NE Iran: Teleseismic, and Strong-Motion Evidence for Rupture Directivity Effects on a Strike-Slip Fault. Journal of Earthquake Engineering, 11(2), 193-214. https://doi.org/10.1080/13632460601031078.
  • Hosseinzadeh, S.R.(2004). Environmental Crises In The Metropolises Of Iran. WIT Press, 179-187. https://doi.org/10.2495/SC040191.
  • Jackson, J.A., McKenzie, D.P. (1984). Active Tectonics of the Alpine-Himalayan Belt Between Western Turkey and Pakistan. Geophysical Journal International, 77 (1), 185–264. 2495/SC04019110.1111/j.1365-246X.1984.tb01931.x.
  • Jackson, J., Haines, J., Holt, W. (1995). The accommodation of Arabia-Eurasia plate convergence in Iran. Journal Of Geophysical Reseach, 100, 15205-15219. https://doi.org/10.1029/95JB01294.
  • Lay, T. & Wallace, T.C. (1995). Modern Global Seismology. California: Academic Press Institute.
  • McKenzie, D. (1972). Active Tectonics of the Mediterranean Region. Geophysical Journal International, 30(2), 109–185. https://doi.org/10.1111/j.1365-246X.1972.tb02351.x.
  • Moradi, S. A., Hatzfeld, D., & Tatar, M. (2011). Microseismicity and Seismotectonics of the North Tabriz Fault (Iran). Tectonophysics, 506(1-4), 22-30. https://doi.org/10.1016/j.tecto.2011.04.008.
  • Nemati, M., Hatzfeld, D., Gheitanchi, M., Sadidkhouy, A., & Mirzaei, N. (2011). Microseismicity and seismotectonics of the Firouzkuh and Astaneh faults (east Alborz, Iran). Tectonophysics, 506, 11-21. http:// org/10.1016/j.tecto.2011.04.007.
  • Nemati, M. (2013). Some Aspects about Seismology of 2012 August 11 Ahar-Varzaghan (Azarbayjan, NW Persia) Earthquakes Sequences. Journal of Sciences Islamic Republic of Iran, 24(3), 229-241.
  • Nemati, M. (2015). Intermediate-term variations in 200-year seismicity at south of Iran. Geomatics Natural Hazards and Risks, 7(3), 1065-1080. https://doi.org/10.1080/19475705.2015.1030785.
  • Ni, J., Barazangi, M. (1986). Seismotectonics of Zagros continental collision zone and a comparison with the Himalayas. Journal Of Geophysical Reseach, 91(B8), 8205-8218. https://doi.org/10.1029/JB091iB08p08205.
  • Priestley, K., Baker, C., & Jackson, J. (1994). Implications of Earthquake Focal Mechanism Data for the Active Tectonics of the South Caspian Basin and Surrounding Regions, Geophysical Journal International, 118(1), 111–141. https://doi.org/10.1111/j.1365-246X.1994.tb04679.x.
  • Solaymani, A.S., Ritz, J.F., Abbassi, M.R. (2011). Left-Lateral Active Deformation along the Mosha–North Tehran Fault System (Iran): Morphotectonics and Paleoseismological Investigations. Tectonophysics, 497(1-4), 1–14. https://doi.org/10.1016/j.tecto.2010.09.013.
  • Stein, S., Wysession, M. (2003). An Introduction to Seismology, Earthquakes and Earth Structure. Oxford: Blackwell Publishing.
  • Tchalenko, J.S. (1975). Seismicity and Structure of the Kopeh Dagh (Iran, USSR). Philosophicasl Transactions of the Royal Society. Series A, Mathematical and Physical Sciences, 278 (1275), 1-28. https://doi.org/10.1098/rsta.1975.0019.
  • Zamani, B., Angelier, J., & Zamani, A. (2008). State of Stress Induced by Plate Convergence and Stress Partitioning in Northeastern Iran, as Indicated by Focal Mechanisms of Earthquakes. Journal of Geodynamics, 45(2-3), 120–132.
  •        https://doi.org/10.1016/j.jog.2007.07.003.
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History

  • Receive Date: 15 July 2023
  • Revise Date: 10 August 2023
  • Accept Date: 18 August 2023

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