Deep Structure and Active Tectonics of the South Aegean Volcanic Arc

Abstract

Abstract Data on spatial distribution of intermediate focal depth earthquakes, fault plane solutions and deep velocity structure have been used to further investigate active tectonics related to the deep structure of the southern Aegean volcanic arc. It is observed that the top layer of the subducted east Mediterranean lithospheric slab is seismically very active at depths 60 – 110 km and 140 – 170 km and that its low seismicity part (110 – 140 km) is under the volcanic arc. This observation, geochemical data and tomographic results suggest that the primary magma reservoir of the Hellenic volcanic arc is in the mantle wedge between the subducted Mediterranean and the overriding Aegean slabs, at depths 60 – 90 km. The genesis of earthquakes at the shallow part of the subducted Mediterranean slab is attributed to dehydration embrittlement of basalt, the low seismicity at intermediate depths is due to increase of temperature and confining pressure and the increase again of seismicity in the lower active part of the slab to a second dehydration embrittlement of hydrous eclogite.