Lithospheric Density Structure of the Aegean Region Constrained by 3D Gravity Modelling

The region of the Aegean Sea, shaped by the subduction of the African plate beneath the Eurasian plate with the intervening Aegean microplate, is one of the most actively deforming areas in the Mediterranean. This system is characterized by strong lateral variations in its tectonic style, where extension in the back arc region has created rifts like the Rifts of Corinth and Evia; volcanic activity in the Southern Aegean Active Volcanic Arc is associated with active subduction along the Hellenic trench; the lateral ocean–continent transition along the Western Hellenic subduction lead to strain partitioning and the formation of Kefalonia strike slip zone, and major strike-slip deformation accommodated by the North Anatolian transform fault associated with west ward motion of Anatolia. Past and ongoing tectonics resulted in a highly heterogeneous lithospheric configuration, which controls the degree of deformation and its localization as reflected by variations in physical properties of the lithosphere.

We present an updated 3D geological model of the Aegean Sea and Hellenic subduction system, which we use to map first-order rheological contrasts in the lithosphere, being constrained by available seismic and seismological observations and by 3D gravity modelling. The model integrates several datasets, including the EPcrust crustal model, available seismic sections, mantle and crustal tomographies, and observed gravity anomalies. The S- and P- wave velocities of the tomographic datasets were converted to densities in order to consistently map 3D density variations in the lithospheric mantle and the crust.

Preliminary gravity modelling results show a good match with observed gravity, fitting regional trends in gravity anomalies across the study area. In a second stage, we carried out a sensitivity analysis to investigate in more details the effect of lithospheric density variations. Specifically, we focused on the transitional domain between the Moho and the upper mantle, where uncertainties in converting seismic velocities to density remain significant.

The model provides new constraints on density variations in the lithosphere, which, especially with the derived strength and temperature contrasts, help to better understand how deformation localizes in the Aegean region.