Lithospheric structure of the eastern Mediterranean Sea: Inferences from surface wave tomography and stochastic inversions constrained by wide-angle refraction measurements

• Published in: Tectonophysics 2021-12, Vol.821, p.229159, Article 229159
• Main Authors: El-Sharkawy, A., Meier, T., Hübscher, C., Lebedev, S., Dannowski, A., Kopp, H., Behrmann, J.H., McGrandle, A., Hamada, M.
• Format: Article
• Language: English
• Subjects: Asthenosphere; Carboniferous; Continental crust; Cooling; Crustal structure; Crustal thickness; Dead Sea Fault; Deformation; Eastern Mediterranean lithosphere; Heterogeneity; Inversions; Joint inversion; Lava; Lithosphere; Ocean basins; Oceanic crust; Plate tectonics; Plates (tectonics); Poisson's ratio; Properties; Seismicity; Surface water waves; Surface wave tomography; Surface waves; Thickness; Tomography; Triassic; Vp/Vs and Poisson's ratio (σ); Wave data; Wave velocity; Wide angle seismic imaging
• ISSN: 0040-1951; 1879-3266
• DOI: 10.1016/j.tecto.2021.229159

The tectonic plate under the eastern Mediterranean Sea shows a remarkable variability as it comprises Earth's oldest oceanic lithosphere as well as the transition towards continental lithosphere beneath the Levant Basin. Its thickness and other properties offer essential information on the lithospheric evolution but have been difficult to determine seismically due to the high heterogeneity of the region and its complex crustal structure. Here, we combine a large, new surface wave dataset with published wide-angle data in order to determine lithospheric properties in the eastern Mediterranean. Our stochastic inversions of broad-band, phase-velocity dispersion measurements resolve the crust-mantle structural trade-offs and yield robust, 1-D shear-wave velocity models down to 300 km depth beneath the Ionian and Levant Basins. The thickness of the crust beneath the two locations is 16.4 ± 3 km and 22.3 ± 2 km, respectively. The Poisson's ratio (σ) of 0.32 and Vp/Vs of 1.93 in the crystalline crust confirm the presence of serpentinized oceanic crust beneath the Ionian Basin. Beneath the Levant Basin, low crustal Vp/Vs (∼ 1.7) and Poisson's (∼ 0.24) ratios indicate continental crust. Beneath the Ionian Basin, the lithosphere is about 180 km thick. By contrast, thin, 75 km thick lithosphere is found beneath the Levant Basin. S-velocity tomography based on surface wave data also shows thick, spatially variable oceanic mantle lithosphere beneath the eastern Mediterranean. Thickness of the oceanic lithosphere increases eastwards from the Triassic Ionian towards the Permo-Carboniferous lithosphere in the Central Eastern Mediterranean. These results demonstrate that oceanic lithosphere can thicken by cooling substantially beyond the limits suggested by the plate cooling model. Beneath the eastern Herodotus oceanic Basin, lithospheric thickness is decreasing to about 180 km. Thin continental lithosphere and shallow asthenosphere are present beneath the Dead Sea Fault, demonstrating that the localization of the lithospheric deformation and crustal seismicity along the fault correlates spatially with the thinning of the underlying continental lithosphere. •Crust and mantle lithospheric structures beneath the eastern Mediterranean Sea are resolved from the joint inversion of surface wave measurements and wide-angle refraction seismics.•Vp/Vs and Poisson's ration estimates point to the presence of serpentinized oceanic crust beneath the Ionian Basin and thinned continental