Eocene to present subduction of southern Adria mantle lithosphere beneath the Dinarides

Abstract

We modeled global positioning system measurements of crustal velocity along a N13°E profile across the southern Adria microplate and south-central Dinarides mountain belt using a one-dimensional elastic dislocation model. We assumed a N77°W fault strike orthogonal to the average azimuth of the measured velocities, but we used a constrained random search algorithm minimizing misfit to the velocities to determine all other parameters of the model. The model fault plane reaches the surface seaward of mapped SW-verging thrusts of Eocene and perhaps Neogene age along the coastal areas of southern Dalmatia, consistent with SW-migrating deformation in an active fold-and-thrust belt. P-wave tomography shows a NE-dipping high-velocity slab to ∼160 km depth, which reaches the surface as Adria, dips gently beneath the foreland, and becomes steep beneath the Dinarides topographic high. The thrust plane is located directly above the shallowly dipping part of the slab. The pattern of precisely located seismicity is broadly consistent with both the tomography and geodesy; deeper earthquakes (down to ∼70 km) correlate spatially with the slab, and shallower earthquakes are broadly clustered around the geodetically inferred thrust plane. The model fault geometry and loading rate, ages of subaerially exposed thrusts in the fold-and-thrust belt, and the length of subducted slab are all consistent with Adria-Eurasia collision involving uninterrupted subduction of southern Adria mantle lithosphere beneath Eurasia since Eocene time.