3-D Crustal Velocity Structure in Northwestern Greece |
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| Authors: | Email author" target="_blank">G?DrakatosEmail author N?Voulgaris M?Pirli N?Melis B?Karakostas |
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| Institution: | (1) National Observatory of Athens, Institute of Geodynamics, 20048, Thission, 118 10 Athens, Greece;(2) Faculty of Geology, Department of Geophysics-Geothermics, Athens University, Panepistimioupolis, Zografou, 157 84 Athens, Greece;(3) Faculty of Geology, Department of Geophysics, University of Thessaloniki, 540 06 Thessaloniki, Greece |
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| Abstract: | — The three-dimensional crustal velocity structure in the area of the northwestern Greek mainland was determined by P-wave travel time inversion, applying a two-step tomography procedure. The data set consists of the travel-time residuals of 584 well located earthquakes. In order to improve the initial (reference) velocity model, before the inversion of travel times, the  minimum 1-D model was determined. Several tests were conducted to estimate model stability and hypocenter uncertainties. The velocity distribution in the shallow layers (4 and 7 km) is strongly affected by the crustal thickness variation and the complex tectonics. A first, well-defined velocity discontinuity appears at a depth of 3–6 km, along the Hellenides Mountain chain. A second low velocity anomaly is detected at a depth of 9–12 km and may be connected with the Alpidic orogenesis. Another interesting feature appears beneath the Amvrakikos Gulf (horstgraben structure), where relatively low velocities (<6.0 km-1) appear to a depth of 20 km. Finally, a well-pronounced velocity boundary is found at a depth of 16 km. In general, low velocities are predominant along the Dinarides-Hellenides Mountain chain, rather typical for the upper crust.Acknowledgement. The authors thank the referees for their useful comments. Moreover, we would like to thank the General Secretariat for Research and Technology of Greece, for the partial support of this study. |
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| Keywords: | Greece crustal structure tomography |
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