Fault slip rates for the active External Dinarides thrust-and-fold belt

Abstract

We present estimates of slip rates for active faults in the External Dinarides. This thrust-and-fold belt formed in the Adria-Eurasia collision zone by the progressive formation of NE-dipping thrusts in the footwalls of older structures. We calculated the long-term horizontal velocity field, slip rates and related uncertainties for active faults using a thin-shell finite element method. We incorporated active faults with different effective fault frictions, rheological properties, appropriate geodynamic boundary conditions, laterally varying heat flow and topography. The results were obtained by comparing the modeled maximum compressive horizontal stress orientations with the World Stress Map database. The calculated horizontal velocities decrease from the southeastern External Dinarides to the northwestern parts of the thrust-and-fold belt. This spatial pattern is also evident in the long-term slip rates of active faults. The highest slip rate was obtained for the Montenegro active fault, while the lowest rates were obtained for active faults in northwestern Slovenia. Low slip rates, influenced by local active diapirism, are also characteristic for active faults in the offshore central External Dinarides. These findings are contradictory to the concept of Adria as an internally rigid, aseismic lithospheric block because the faults located in its interior release a part of the regional compressive stress. We merged the modeling results and available slip rate estimates to obtain a composite solution for slip rates.