مطالعه ساختار سرعت موج برشی در شرق ایران با استفاده از توموگرافی امواج ریلی

نوع مقاله : مقاله پژوهشی‌

نویسندگان

1 دانشجوی دکتری، دانشگاه تحصیلات تکمیلی علوم پایه، زنجان، ایران

2 دانشیار، دانشگاه تحصیلات تکمیلی علوم پایه، زنجان، ایران

3 محقق، پژوهشگاه بین‌المللی زلزله شناسی و مهندسی زلزله، تهران، ایران

چکیده

در این مطالعه سامانه سنگ‌کره- ‌سست‌کره شرق ایران با استفاده از روش­های توموگرافی با فرض دو جبهه موج تخت و توموگرافی دورلرز بررسی شده است. برای این منظور از 5862 شکل موج ریلی ثبت­شده در چهل ایستگاه لرزه­نگاری برای تولید نقشه­های سرعت فاز در نُه باند فرکانسی از 25 ثانیه تا 111 ثانیه استفاده شد. سپس با وارون­سازی منحنی­های پاشش محلی حاصل از نقشه­های سرعت فاز در دوره تناوب­های مختلف، مدل سه­بعدی سرعت موج برشی از سطح تا عمق 200 کیلومتر ساخته شد. ساختار سرعت سه­بعدی تعیین­شده، یک کانال کم­سرعت سست‌کره‌ای را مشخص می­کند که زیر یک سنگ‌کره نازک قرار گرفته است. با رسم مقدار سرعت موج برشی به اندازه 1/4 کیلومتر بر ثانیه، نقشه ضخامت پوسته‌ای (عمق موهو) برای منطقه تعیین شد. نقشه موهو نشان می­دهد ضخامت تقریبی بیشتر منطقه مورد مطالعه، 36 کیلومتر است که با ضخامت یک پوسته با تغییر شکل کم متناظر است. همچنین دو پوسته ضخیم، زیر کمان آتشفشانی ارومیه- دختر و در بخش شمالی منطقه مورد مطالعه وجود دارد؛ یعنی در جایی که رخنمون­های افیولیتی زمین­درز نئوتتیس را مشخص می­کند. به احتمال زیاد این ضخیم‌شدگی­ها به دلیل تغییر شکل در مقیاس سنگ‌کره‌ای در منطقه زمین­درز نئوتتیس است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Investigation of shear wave velocity model beneath east of Iran from Rayleigh waves tomography

نویسندگان [English]

  • Zahra Zarunizadeh 1
  • Khalil Motaghi 2
  • Ramin Movaghari 3
1 Ph.D. Student, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan, Iran
2 Associate Professor, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan, Iran
3 Researcher, International Institute of Earthquake Engineering and Seismology, Tehran, Iran
چکیده [English]

The Iranian Plateau is a part of the Alpine–Himalayan orogenic belt located in the western part of Asia. Convergence of the Arabian Plate and Eurasia from the late Cretaceous to the present has generated significant lithospheric deformations such as crustal shortening and thickening in the Plateau and surrounding mountain ranges including the Zagros Fold–Thrust Belt, Alborz and Kopeh Dagh. The convergence across Zagros is accommodated through different mechanisms of diffused shortening and/or thrusting of the Arabian lithosphere beneath Central Iran. This study focuses on the velocity structure of the eastern part of the Iranian Plateau which has not been studied well yet. Our study region also contains Binalud and Kopeh-Dagh deformation domains which were built up by the north-eastern collisional boundary between the Plateau and Eurasia and a small part of the Urumieh-Dokhtar magmatic arc which was the volcanic arc of the past Neotethyan subduction.
    The lithosphere-asthenosphere system beneath east of Iran is investigated by employing earthquake surface wave tomography. A total of 5862 teleseismic Rayleigh waveforms from 368 events recorded at three permanent networks during a period of three years were used to produce 2-D high-resolution phase velocity maps. We employed a two-plane wave tomography approach to generate phase velocity maps at period ranges of 25–111 s. From a published study of ambient noise tomography, we extracted Rayleigh wave dispersion data at 8–20 s periods to improve resolution in the crust and then inverted them for a 3-D S-wave velocity model. A 3-D velocity model was then constructed by a nonlinear Bayesian Markov chain Monte-Carlo algorithm of local node-wise dispersion data into S-wave velocity models down to a depth of 200 km. The most prominent resolved feature by our 3-D velocity model is a low-velocity asthenospheric channel at 70 and 150 km depths overlaid by a thin lithosphere. We believe that in the lack of an isostatic compensated crustal root in the Iranian Plateau, this feature is supporting high elevation (~1000 m) topography covering the Iranian Plateau. A Moho map for the study region is obtained by mapping the geometry of 4.0 km/s S-wave velocity contour in the 3-D velocity model. It shows that most of the study region is covered by a less deformed crust with a thickness of ~36 km. Two crustal roots are observed, one beneath the Urumieh-Dokhtar magmatic arc and the other beneath the north-eastern part of the study region where an array of the Neotethys suture zones is marked by ophiolite outcrops. Lithospheric scale deformation in a sequence of Neotethys suture zones is high probably responsible for the crustal thickening in NE Iran.
 

کلیدواژه‌ها [English]

  • Tomography
  • Rayleigh waves
  • shear wave velocity
  • lithosphere
  • east of Iran
Abdulnaby, W., Motaghi, K., Shabanian, E., Mahdi, H., Al‐Shukri, H., and Gök, R., 2020, Crustal structure of the Mesopotamian Plain, east of Iraq: Tectonics, 39, e2020TC006225. doi.org/10.1029/2020TC006225.
Afonso, J., Fullea, J., Griffin, W., Yang, Y., Jones, A., Connolly, J., and O'Reilly, S., 2013, 3‐D multi observable probabilistic inversion for the compositional and thermal structure of the lithosphere and upper mantle, I: A priori petrological information and geophysical observables: Journal of Geophysical Research: Solid Earth, 118, 2586-2617.
Agard, P., Omrani, J., Jolivet, L., and Mouthereau, F., 2005, Convergence history across Zagros (Iran): constraints from collisional and earlier deformation: International Journal of Earth Sciences, 94(3), 401–419.
Alinaghi, A., Koulakov, I., and Thybo, H., 2007, Seismic tomographic imaging of P-and S-waves velocity perturbations in the upper mantle beneath Iran: Geophysical Journal International, 169(3), 1089-1102.
Camp, V. E., and Griffis, R. J., 1982, Character, genesis and tectonic setting of igneous rocks in the Sistan suture zone, eastern Iran: Lithos, 15, 221–239.
 
Egan, S. S., Mosar, J., Brunet, M. F., and Kangarli, T., 2009, Subsidence and uplift mechanisms within the South Caspian Basin: insights from the onshore and offshore Azerbaijan region: Geological Society of London, Special Publications, 312(1), 219–240.
Forsyth, D. W., and Li, A., 2005, Array-analysis of two-dimensional variations in surface wave phase velocity and azimuthal anisotropy in the presence of multi-pathing interferece, in Seismic Earth: Array Analysis of Broadband Seismograms: Geophysical Monograph Series, 157, AGU, Washington DC.
Gök, R., Mahdi, H., Al-Shukri, H., and Rodgers, J. A., 2008, Crustal structure of Iraq from receiver functions and surface wave dispersion: Implications for understanding the deformation history of the Arabian-Eurasian collision: Geophysical Journal International, 172, 1179-1187.
Guo, Z., Chen, Y. J., Ning, J., Yang, Y., Afonso, J. C., and Tang, Y., 2016, Seismic evidence of on-going sublithosphere upper mantle convection for intra-plate volcanism in Northeast China: Earth and Planetary Science Letters, 433, 31-43.
Hatzfeld, D., and Molnar, P., 2010, Comparisons of the kinematics and deep structures of the Zagros and Himalaya and of the Iranian and Tibetan plateaus and geodynamic implications: Reviews of Geophysics, 48(2), RG2005, doi:10.1029/2009RG000304.
Hessami, K., Jamali, F., and Tabassi, H., 2003, Major Active Faults of Iran, edition 2003: International Institute of Earthquake Engineering and Seismology.
Homke, S., Vergés, J., van der Beek, P. A., Fernàndez, M., Saura, E., Barbero, L., Badics, B., and Labrin, E., 2010, Insights in the exhumation history of the NW Zagros from bedrock and detrital apatite fission-track analysis: evidence for a long-lived orogeny: Basin Research, 22(5), 659–680.
Koulakov, I., 2011, High‐frequency P and S velocity anomalies in the upper mantle beneath Asia from inversion of worldwide traveltime data: Journal of Geophysical Research: Solid Earth, 116(B4).
Madanipour, S., Ehlers, T. A., Yassaghi, A., Rezaeian, M., Enkelmann, E., Bahroudi, A., 2013, Synchronous deformation on the orogenic plateau margins, insights from the Arabia-Eurasia collision: Tectonophysics, 608, 440–451.
Maggi, A., and Priestley, K., 2005. Surface waveform tomography of the Turkish–Iranian plateau: Geophysical Journal International, 160(3), 1068-1080.
Masters, G., Barmine, M., and Kientz, S., 2007, Mineos User’s Manual in Computational Infrastructure for Geodynamics: California Institute of Technology, Pasadena.
Mohammadi, E., Sodoudi, F., Kind, R., and Rezapour, M., 2013, Presence of a layered lithosphere beneath the Zagros collision zone: Tectonophysics, 608, 366-375.
Motaghi, K., Shabanian, E., and Kalvandi, F., 2017a, Underplating along the northern portion of the Zagros suture zone, Iran: Geophysical Journal International, 210(1), 375–389.
Motaghi, K., Shabanian, E., Tatar, M., Cuffaro, M., and Doglioni, C., 2017b, The south Zagros suture zone in teleseismic images: Tectonophysics, 694, 292–301.
Motaghi, K., Tatar, M., and Priestley, K., 2012a, Crustal thickness variation across the northeast Iran continental collision zone from teleseismic converted waves: Journal of Seismology, 16, 253–260.
Motaghi, K., Tatar, M., Shomali, Z. H., Kaviani, A., and Priestley, K., 2012b, High resolution image of uppermost mantle beneath NE Iran continental collision zone: Physics of the Earth and Planetary Interiors, 208–209, 38–49.
Motaghi, K., Tatar, M., Priestley, K., Romanelli, F., Doglioni, C., and Panza, G. F., 2015, The deep structure of the Iranian Plateau: Gondwana Research, 28(1), 407–418.
Mouthereau, F., Lacombe, O., Verges, J., 2012, Building the Zagros collisional orogen: Timing, strain distribution and the dynamics of Arabia/Eurasia plate convergence: Tectonophysics, 532–535, 27–60.
Movaghari, R., Javan Doloei, G., 2020, 3-D crustal structure of the Iran plateau using phase velocity ambient noise tomography: Geophysical Journal International, 220(3), 1556-1568.
Movaghari, R., Javan Doloei, G., Yang, Y., Tatar, M., and Sadidkhouy, A., 2021, Crustal radial anisotropy of the Iran plateau inferred from ambient noise tomography: Journal of Geophysical Research, Solid Earth, 126(4), e2020JB020236.
Paul, A., Kaviani, A., Hatzfeld, D., Tatar, M., and Pequegnat, C., 2010, Seismic imaging of the lithospheric structure of the Zagros mountain belt (Iran), in Tectonic and Stratigraphic Evolution of Zagros and Makran During the Meso-Cenozoic: Geological Society, Special Publications, 330, 5–18.
Paul, A., Kaviani, A., Hatzfeld, D., Vergne, J., and Mokhtari, M., 2006, Seismological evidence for crustal-scale thrusting in the Zagros mountain belt (Iran): Geophysical Journal International, 166, 227–237.
Press, W. H., Teukolsky, S. A., Vetterling, W. T., and Flannery, B. P., 1992, Numerical Recipes in FORTRAN: The Art of Scientific Computing, 2nd edition: Cambridge University Press, New York.
Priestley, K., McKenzie, D., Barron, J., Tatar, M., and Debayle, E., 2012, The Zagros core: Deformation of the continental lithospheric mantle: Geochemistry, Geophysics, Geosystems, 13(11), 1–21.
Priestley, K., McKenzie, D., 2006, The thermal structure of the lithosphere from shear wave velocities: Earth and Planetary Science Letters, 244(1-2), 285-301.
Rastgoo, M., Rahimi, H., Motaghi, K., Shabanian, E., Romanelli, F., and Panza, G. F., 2018, Deep structure of the Alborz Mountains by joint inversion of P receiver functions and dispersion curves: Physics of the Earth and Planetary Interiors, 277, 70-80.
Sengor, A. M. C., 1996, Paleotectonics of Asia: fragments of a synthesis: The Tectonic Evolution of Asia, 486-640.
Shad Manaman, N., and Shomali, H., 2010, Upper mantle S-velocity structure and Moho depth variations across Zagros belt, Arabian–Eurasian plate boundary: Physics of the Earth and Planetary Interiors, 180(1-2), 92-103.
Shad Manaman, N., Shomali, H., and Koyi, H., 2011, New constraints on upper-mantle S-velocity structure and crustal thickness of the Iranian plateau using partitioned waveform inversion: Geophysical Journal International, 184, 247–267.
Shapiro, N., and Ritzwoller, M., 2002, Monte-Carlo inversion for a global shear-velocity model of the crust and upper mantle: Geophysical Journal International, 151, 88-105.
Shen, W., Ritzwoller, M. H., Schulte-Pelkum, V., and Lin, F. C., 2012, Joint inversion of surface wave dispersion and receiver functions: a Bayesian Monte-Carlo approach: Geophysical Journal International, 192, 807-836.
Shomali, Z. H., Keshvari, F., Hassanzadeh, J., and Mirzaei, N., 2011, Lithospheric structure beneath the Zagros collision zone resolved by non-linear teleseismic tomography: Geophysical Journal International, 187(1), 394-406.
Simmons, N. A., Myers, S. C., and Johannesson, G., 2011, Global‐scale P wave tomography optimized for prediction of teleseismic and regional travel times for Middle East events: 2. Tomographic inversion: Journal of Geophysical Research: Solid Earth, 116(B4).
Taghizadeh-Farahmand, F., Afsari, N., and Sodoudi, F., 2015, Crustal thickness of Iran inferred from converted waves: Pure and applied Geophysics, 172, 309– 331.
Tarantola, A., and Valette, B., 1982, Generalized non-linear problems solved using the least-squares criterion: Reviews of Geophysics, 20, 219–232.
Tarantola, A., 2005, Inverse Problem Theory and Methods for Model Parameter Estimation: Society for Industrial and Applied Mathematics.
Teknik, V., Ghods, A., Thybo, H., and Artemieva, I. M., 2019, Crustal density structure of the northwestern Iranian Plateau: Canadian Journal of Earth Sciences, 56(12), 1347-1365.
Tirrul, R., Bell, I. R., Griffis, R. J., and Camp, V. E., 1983, The Sistan suture zone of eastern Iran: Geological Society of America Bulletin, 94, 134–150.
Wu, Z., Chen, L., Talebian, M., et al., 2021, Lateral structural variation of the lithosphere‐asthenosphere system in the northeastern to eastern Iranian plateau and its tectonic implications: Journal of Geophysical Research: Solid Earth, 2020JB020256, https://doi.org/10.1029/2020JB020256.
Yang, Y., and Forsyth, D. W., 2006, Regional tomographic inversion of amplitude and phase of Rayleigh waves with 2-D sensitivity kernels: Geophysical Journal International, 166, 1148–1160.
Zarrinkoub, M. H., Pang, K. N., Chung, S. L., Khatib, M. M., Mohammadi, S. S., Chiu, H. Y., and Lee, H. Y., 2012, Zircon U–Pb age and geochemical constraints on the origin of the Birjand ophiolite, Sistan suture zone, eastern Iran: Lithos, 154, 392-405.
Zhou, L., Xie, J., Shen, W., Zheng, Y., Yang, Y., Shi, H., and Ritzwoller, M. H., 2012, The structure of the crust and uppermost mantle beneath South China from ambient noise and earthquake tomography: Geophysical Journal International, 189(3), 1565–1583.