Crustal velocity structure of Kerman Region from joint inversion of receiver functions and Rayleigh waves group velocity dispersion


1 Student/Graduate University of Advanced Technology

2 Assistant Professor/Graduate University of Advanced Technology

3 Assistant Professor/ Graduate University of Advanced Technology


Iran is situated in one of the world's seismic regions and the possibility of destructive earthquakes in most regions of the country has given great significance to recognition of Iranian seismic nature from a seismic and seismotectonic standpoint. Study of the crust and upper mantle velocity structure in the Iranian plateau provides better understanding of its evolution and tectonic history of seismotectonic zones. Crustal velocity structure is used as initial information for various geological and geophysical studies, and therefore it is a basic and important issue in seismology. Receiver functions show Earth local structure response to P-wave vertical arrival approximately beneath of a three-component seismometer and are sensitive to shear-wave velocity impedance. Depth-velocity trade-off in RFs information is causing of inversion non-uniqueness problem, but one can overcome to this limitation by incorporating information from absolute velocity from dispersion estimations and joint inversion of this two data sets. By this, more exact constraints are provided about crustal structure. In this study, crustal velocity structure and Moho discontinuity depth beneath of four broadband stations of Kerman seismological network have been investigated from joint inversion of P-wave receiver functions (RFs) and Rayleigh wave group velocity dispersion. The teleseismic waveformes in time interval more than two years was used to compute RFs from the time domain iterative deconvolution procedure Ligorria and Ammon (1999) which has higher stability with noisy data compared to frequency-domain methods. The 165 desired RFs were computed from these waveforms that have magnitude bigger than 5.5 and have recorded at four permanent stations in epicentral distance 25˚-90˚. To delete high frequencies, Gaussian parameter 1.0 used. For increasing signal to noise ratio, RFs clustered in 10˚ azimuthal and less than 15˚ epicentral distance ranges. Finally, the RFs were stacked. This work performed under software SAC. Due to changes in group and phase velocity of surface waves with depth for different periods and dispersion in these waves and sensitivity of the waves dispersion curve to shear wave velocity, inversion of dispersion curve is an efficient method for determining the average shear wave velocity in a vast region of the depth between two seismic stations. Group velocity dispersion curves were incorporated into our joint-inversion scheme from an independent regional fundamental-mode Rayleigh waves tomography images for within the 20–80s period range in Iran by Rahimi et al. (2014). Joint inversion of two independent data sets was performed with considering combination weighting parameter appropriate performed from Herrmann and Ammon program (2003). Minimizing standard error between real and predicted data is the criteria for getting to desired final and close to earth real model.
The results from this study show that Moho discontinuity boundary is beneath of CHMN station at 52±2 km depth, beneath of KHGB station at 50±2 km depth, beneath of NGRK station at 54±2 km depth and beneath of TVBK station at 52±2 km depth. We used forward modeling test for error estimation and resulting models accuracy.
Relative high crustal thickness in this region compared to other regions of central Iran can be attributed to abut the region to the Sanandaj–Sirjan zone (SSZ) and Urumieh–Dokhtar magmatic assemblage (UDMA) that underthrusting of the Arabian plate beneath Central Iran along the main Zagros thrust fault is caused of thickening. It can also attributed to exist of thick Magma masses in Urumieh–Dokhtar magmatic assemblage and increase the density and relative thickness of the area based on the Isostasy theory.


Main Subjects

نصرآبادی، ا.، تاتار، م. و کاویانی، 1.، 1390، ساختار پوستۀ ایران براساس برگردان همزمان تابع انتقال گیرنده و اطلاعات پاشندگی سرعت فاز امواج ریلی، فصلنامۀ علوم زمین، 82، 83-94.
Alavi, M., 1994, Tectonics of the Zagros orogenic belt of Iran: new data and interpretations, Tectonophysics, 229, 211-238.
Ammon, C. J., 1991, The isolation of receiver effects from teleseismic P waveforms. Bull. seism. Soc. Am., 81, 2504-2510.
Ammon, C. J., Randall, G. E. and Zandt, G., 1990, On the nonuniqueness of receiver functions, J. Geophys. Res., 95, 15303-15318.
Asudeh, I., 1982, Seismic structure of Iran from surface and body wave data, J. Geophys. Res., 71, 715-730.
Berberian, M., 1981, Active faulting and tectonics of Iran, Geodynamics, 3, 33-69.
Berberian, M. and King, G. C. P., 1981, Towards a palaeogeography and tectonic evolution of Iran, Canadian Journal of Earth Science, 18, 210-265.
Berberian, M., Jackson, J. A., Fielding, E. J., Parsons, B. E., Priestley, K., Qorashi, M., Talebian, M., Walker, R., Wright, T. J. and Baker, C., 2001, The 1998 March 14 Fandoqa earthquake (Mw 6.6) in Kerman province, southeast Iran: Re-rupture of the 1981 Sirch earthquake fault, triggering of slip on adjacent thrusts and the active tectonics of the Gowk fault zone, Geophysical Journal International, 146, 371-398.
Davoodzdeh, M. and Schmidt, K., 1983, A Review of the Mesozoic Paleogeography and Palaotectonic Evolution of Iran, in geodinamyic peroject in Iran, 51, 415-435.
Dehghani, G. A. and Makris, J., 1984, The gravity field and crustal structure of Iran, Neues Jahrbuch Geol, Paleont, Abh, 168, 215-229.
Ghasemi, A. and Talbot, C. J., 2006, A new tectonic scenario for the Sanandaj-Sirjan Zone (Iran), Journal of Asian Earth Sciences, 26, 683-693.
Giese, P., Makris, J., Akashe, B., Rower, P., Letz, H. and Mostaanpour, M., 1983, Seismic crustal studies in southern Iran between the Central Iran and Zagros belt, Geological Survey of Iran, 51, 71-89.
Herrmann, R. B. and Ammon, C. J., 2003, Computer programs in seismology, Version 3.20, Surface waves, receiver functions and crustal structure, Saint Louis University, Penn State University.
Jackson, J. A. and McKenzie, D. P., 1984, Active tectonics of the Alpine-Himalayan belt between western Turkey and Pakistan, Geophys. J. R. Astr. Soc., 77, 185-264.
Julia, J., Ammon, G. J. and Nyblade, A. A., 2005, Evidence for mafic lower crust in Tanzania, East Africa, from joint inversion of receiver functions and Rayleigh wave dispersion velocities, Geophys. J. Int., 162, 555-569.
Ligorrı´a, J. P. and Ammon, C. J., 1999, Iterative deconvolution and receiver function estimation, Bull. Seismol. Soc. Am., 89, 1395-1400.
Ozalaybey, S., Savage, M. K., Sheehan, A. F., Louie, J. N. and Brune, J. N., 1997, Shear-wave velocity structure in the northern basin and range province from the combined analysis of receiver functions and surface waves, Bull. Seismol. Soc. Am., 87, 183-199.
Paul, A., Kaviani, A., Hatzfeld, D., Vergne, J. and Mokhtari, M., 2006, Seismological evidence for crustal-scale thrusting in the Zagros mountain belt (Iran), Geophys. J. Int., 166, 227-237.
Rahimi, H., Hamzehloo, H., Vaccari, F. and Panza, G. F., 2014, Shear-wave velocity tomography of the lithosphere–asthenosphere system beneath the Iranian Plateau, Bull. Seismol. Soc. Am., 104(6), 2782-2798.
Rham, D., 2009, The crustal structure of the Middle East, Ph.D. thesis, University of Cambridge Library, Cambridge, UK.
Tatar, M. R. and Nasrabadi, A., 2013, Crustal thickness variations in the Zagros continental collision zone (Iran) from joint inversion of receiver functions and surface wave dispersion, Journal of Seismology, 17, 1321-1337.
Vernant, P., Nilforoushan, F., Hatzfeld, D., Abbassi, M., Vigny, C., Masson, F., Nankali, H., Martinod, J., Ashtiani, A., Bayer, R., Tavakoli, F. and Ch´ery, J., 2004, Present-day crustal deformation and plate kinematics in the Middle East constrained by GPS easurements in Iran and northern Oman, Geophys. J. Int., 157, 381-398.
Walker, R. and Jackson, J., 2004, Active tectonics and late Cenozoic strain distribution in central and eastern Iran, Tectonics, 23, doi: 10.1029/2003TC001529.
Wilson, D., Aster, R., Ni, J., Grand, S., West, M., Gao, W., Baldridge, W. S. and Semken, S., 2005, Imaging the seismic structure of the crust and upper mantle beneath the Great Plains, Rio Grande Rift, and Colorado Plateau using receiver functions, J. Geophys. Res., 110, B05306, doi: 10.1029/2004JB003492.