Whole-mantle tomography beneath eastern Mediterranean and adjacent regions

SUMMARY The Mediterranean and its surrounding regions are characterized by strong interactions of the Eurasian, African and Arabian Plates, as well as several microplates, resulting in significant seismic and volcanic activities. In addition, this region has a complex history of plate movements, leading to the formation of distinct orogenies such as the Alps, Apennines and Carpathians, as well as a complex distribution of subducted slabs in the mantle. Intermediate-depth earthquakes actively occur in the subducting Vrancea slab beneath Romania. Furthermore, volcanic activity in the Caucasus and Arabian Peninsula may be stimulated by mantle plumes. To better understand the complex tectonics and seismic and volcanic activities, we need to study the detailed 3-D structure of the crust and mantle beneath this region. However, previous studies did not thoroughly investigate the 3-D structure of the whole mantle, particularly the lower mantle. Here, we apply the updated global tomography method to reveal the 3-D P-wave velocity (${V_P}$) structure of the whole mantle beneath this region. We use ∼7 million P, pP, PP, PcP and Pdiff wave arrival times of 21 629 earthquakes recorded at 14 283 seismograph stations worldwide. The resulting ${V_P}$ tomography clearly shows stagnation of the subducted African and Tethys slabs above the 660-km discontinuity, although a portion of the slab penetrates the 660-km discontinuity and sinks into the lower mantle. A big mantle wedge has formed above the stagnant slab, which may affect the surface topography and seismic activity such as the Vrancea intermediate-depth earthquakes. A window appears between the subducting Hellenic and Cyprus slabs. Given the development of subslab hot mantle upwelling (SHMU) beneath this region, an extensive volcanic eruption in the Aegean Sea area might be powered by a mixture of island arc magma and SHMU through the slab window. Intraplate volcanoes in the Arabian Peninsula and Caucasus may be fed by hot mantle plumes rising from the core–mantle boundary.