Contributors: Department of Geological Sciences, University of Missouri-Columbia , Columbia, MO 65211, USA; Earth Science and Engineering Program, Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Department of Seismology, P.O. Box: 23955-6900 Thuwal, Kingdom of Saudi Arabia; Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IRD, IFSTTAR, ISTerre , Grenoble 38041, France; Institute of Geosciences, Goethe-University Frankfurt, Department of Geophysics , Frankfurt/Main 60438, Germany; Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione Bologna, Bologna, Italia; Department of Earth Sciences, University of Cambridge , Downing St, Cambridge CB2 3EQ, UK; Institute of Geophysics, University of Tehran, Department of Seismology , P.O. Box: 14155-6466 Tehran, Iran; Institute of Geosciences, Goethe-University Frankfurt, Department of Geophysics, Frankfurt/Main 60438, Germany
نبذة مختصرة : We have constructed a 3-D shear wave velocity (Vs) model for the crust and uppermost mantle beneath the Middle East using Rayleigh wave records obtained from ambient-noise cross-correlations and regional earthquakes. We combined one decade of data collected from 852 permanent and temporary broad-band stations in the region to calculate group-velocity dispersion curves. A compilation of >54 000 ray paths provides reliable group-velocity measurements for periods between 2 and 150 s. Path-averaged group velocities calculated at different periods were inverted for 2-D group-velocity maps. To overcome the problem of heterogeneous ray coverage, we used an adaptive grid parametrization for the group-velocity tomographic inversion. We then sample the period-dependent group-velocity field at each cell of a predefined grid to generate 1-D group-velocity dispersion curves, which are subsequently inverted for 1-D Vs models beneath each cell and combined to approximate the 3-D Vs structure of the area. The Vs model shows low velocities at shallow depths (5–10 km) beneath the Mesopotamian foredeep, South Caspian Basin, eastern Mediterranean and the Black Sea, in coincidence with deep sedimentary basins. Shallow high-velocity anomalies are observed in regions such as the Arabian Shield, Anatolian Plateau and Central Iran, which are dominated by widespread magmatic exposures. In the 10–20 km depth range, we find evidence for a band of high velocities (>4.0 km s–1) along the southern Red Sea and Arabian Shield, indicating the presence of upper mantle rocks. Our 3-D velocity model exhibits high velocities in the depth range of 30–50 km beneath western Arabia, eastern Mediterranean, Central Iranian Block, South Caspian Basin and the Black Sea, possibly indicating a relatively thin crust. In contrast, the Zagros mountain range, the Sanandaj-Sirjan metamorphic zone in western central Iran, the easternmost Anatolian plateau and Lesser Caucasus are characterized by low velocities at these depths. Some of these anomalies may be ...
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