Document Type : Original Research Paper

Authors

1 Assistant Professor, Faculty of Sciences & Earthquake Research Center , Faculty of Physics, University of Kerman (Shahid Bahonar), Kerman, Iran; Geological Survey of Iran (GSI), Teheran, Iran

2 Assistant Professor, Geological Survey of Iran (GSI), Seismotectonic and Seismology Group (SSD), Teheran, Iran

3 PhD. Student, Geological Survey of Iran (GSI), Seismotectonic and Seismology Group (SSD), Teheran, Iran

4 Master of Science, Geological Survey of Iran (GSI), Seismotectonic and Seismology Group (SSD), Teheran, Iran

Abstract

A MN=5.8 (Institute of Geophysics Seismological Center, University of Tehran) earthquake in 2010 July 20 shook southeastern Zagros, over the active ramp of the Mountain Front Fault (MFF). A body killed during the earthquake and it’s aftershocks have affected hundreds of square kilometers around the epicenter. The shook area has experienced many moderate to large earthquakes at the historical time and the MFF recognized as their responsible. With the combination of the waveforms of seismological networks for the Institute of Geophysics, University of Tehran, International Institute of Earthquake Engineering and Seismology of Iran and a local network of the Geological Survey of Iran at Fars province, the source parameters of the earthquake were modified. For this event the ML magnitude computed 5.4 and a depth of 10 km were estimated. This event is related to the growing of anticlines neighboring the MFF with a fault propagated through their cores as of the other reverse earthquakes in Zagros. Tilting and uplifting of young alluvial deposits neighboring them are evidences for this growing. The iso-seismal curves elongated along MFF and the maximum intensity in MM and JMA scales was estimated VII. A small conjugate shear zone with maximum 1 km elongation, 150 m width and 10 cm of both vertical and right lateral dislocations with the strike of N45˚E, was mapped. Finally for this earthquake there was not any rupture except this T kind rupture which not merits the earthquake magnitude.

References
Agard, P., Omrani, J., Jolivet, L. & Mouthereau, F., 2005- Convergence history across Zagros (Iran): constraints from collisional and earlier deformation, Int. J. Earth Sci., 94, 401–419.
Alavi, M., 2004- Regional stratigraphy of the Zagros fold-thrust belt of Iran and its proforeland evolution, Am.J.Sci., 304, 1–20.
Ashtari, M., Hatzfeld, D. and Kamalian, N., 2005- Microseismicity in the region of Tehran, Tectonophysics, 395, 193–208.
Bachmanov, D.M., Trifonov, V.G., Hessami, K.T., Kozhurin, A.I., Ivanova, T.P., Rogozhin, E.A., Hademi, M.C. & Jamali, F.H., 2004 - Active faults in the Zagros and central Iran, Tectonophysics, 380, 221–241.
Berberian M., 1995- Master blind thrust faults hidden under the Zagros folds: active basement tectonics and surface morphotectonic, Tectonophysics 241 193-224.
Falcon, N., 1969- Problems of the relationship between surface structure and deep displacements illustrated by the Zagros Range, in Time and Place in Orogeny, Geological Society (London) Special Publication, 3, 9 – 22.
Hatzfeld, D., Authemayou, C., van der Beek, P., Bellier, O. Lavé, J., Oveisi, B., Tatar, M., Tavakoli, F., Walpersdorf , A. and Yamini-Fard, F., 2010 - The kinematics of the Zagros Mountains (Iran), Geological Society, London, Special Publications; v. 330; p. 19-42.
Havskov, J., Ottemöller, L., 2005- SEISAN: the earthquake analysis software, version 8.1.
Jackson J. and McKenzie D., 1988- The relationship between plate motions and seismic moment tensors and the rates of active deformation in the Mediterranean and Middle East. Geophysical Journal of the Royal Astronomical Society, 83, 45–73.
Masson, F., Che´ry, J., Htzfeld, D., Martinoid, J., Vernant, P., Tavakoli,F. and Ghafory Ashtiani, M., 2005- Seismic versus aseismic deformation in Iran inferred from earthquakes and geodetic data. GJI, 160, 217–226.
Mcquarrie, N.,. 2004- Crustal scale geometry of the Zagros fold–thrust belt, Iran. Journal of Structural Geology, 26, 519–535.
Nemati, M., Hatzfeld, D., Gheitanchi, M., Sadidkhouy, A. and Mirzaei, N., 2011-  Microseismicity and seismotectonics of the Firouzkuh and Astaneh faults (east Alborz, Iran), Tectonophysics, 506 (2011) 11-21, doi: 1016/j.tecto.2011.04.007.
Ni, J. and Barazangi, M., 1986- Seismotectonics of Zagros continental collision zone and a comparison with the Himalayas. J. Geophys. Res., 91(B8): 8205-8218.
Oveisi, B., Lave´, J. and Van De Beek, P. , 2007- Rates and processes of active folding evidenced by Pleistocene terraces at the central Zagros front (Iran).In: Thrust Belt and Foreland Basin. Frontiers in Earth Sciences. Springer-Verlag, New York, 265–285.
Oveisi, B., Lave´, J., Van Der Beek, P., Carcaillet, J., Benedetti, L., Braucher, R. and Aubourg, C., 2009- Thick- and thin-skinned deformation rates in the Zagros Simple Folded Zone (Iran) indicated by displacement of geomorphic surfaces. Geophysical Journal International, 176, 627–654.
Sepehr, M., Cosgrove, J. and Moieni, M., 2006- The impact of cover rock rheology on the style of folding in the Zagros fold-thrust belt. Tectonophysics 427 (2006) 265–281.
Talbot, 1998- Extrusionof Hormoz salt in Iran, Geol. Soc. Spec. Publ. London, 143, 315-334.
Talebian, M. and Jackson, J., 2004- A reappraisal of earthquake focal mechanisms and active shortening in the Zagros mountains of Iran. Geophysical Journal International, 156, 506–526.
Tatar, M., Jackson, J., Hatzfeld, D. and Bergman, E., 2007- The 2004 May 28 Baladeh earthquake (Mw 6.2) in the Alborz, Iran: over thrusting the South Caspian Basin margin, partitioning of oblique convergence and the seismic hazard of Tehran, Geophys J. Int., 170, 249–261.
Tatar, M., Hatzfeld, D. and Ghafoury-Ashtiani, M. 2004- Tectonics of the Central Zagros (Iran) deduced from microearthquake seismicity. Geophysical Journal International, 156, 255–266.
Walpersdorf, A., Hatzfeld, D. , Nankali, H., Tavakoli, F., Nilforoushan, F., Tatar, M., Vernant, P. , Chéry, J. and  Masson, F., 2006- Difference in the GPS deformation pattern of North and Central Zagros (Iran), Geophys. J. Int., 167, 1077–1088, doi:10.1111/j.1365- 246X.2006.03147.
Wessel, P. and Smith, W. H. F., 1998- New, improved version of Generic Mapping Tools released, EOS, Trans. Am. geophys. Un., 79(47), 579.
Yamini-Fard, F., Hatzfeld, D., Tatar, M. and Mokhtari, M., 2006- Microearthquake seismicity at the intersection between the Kazerun Fault and the Main Recent Fault (Zagrs, Iran), Geophys. J. Int., doi:10.1111/j.1365- 246X.2006.02891.x.
Vernant, P., Nilforoushan, F., Chéry, J., Bayer, R., Djamour, Y., Masson, F., Nankali, H., Ritz, J.-F., Sedighi, M. and Tavakoli, F., 2004- Deciphering oblique shortening of central Alborz in Iran using geodetic data, Earth and Planetary Science Letter, 223, 177–185.