Alpine lithospheric strength and its relation to seismicity distribution

Despite the amount of research focused on the Alpine orogen, different hypotheses still exist regarding varying seismicity distribution patterns throughout the numerous crustal blocks of different physical properties that comprise the region. The thermal field, also varying as a consequence of heterogeneous lithospheric properties, is a key controlling factor for rock strength via thermally activated creep and it exerts a first order influence on the depth of the brittle-ductile transition zone, the lower bound to the seismogenic zone and the spatial distribution of seismicity. Previous measurement constrained works across the orogen and its forelands that have defined the 3D lithospheric density distribution and thermal field facilitate the generation of an observation based rheological model of the region. Here we present rheological modelling results from across the Alps and their forelands and compare calculated strengths to observed seismicity patterns, in order to explain the localisation of deformation. The depth of peak seismic energy release in almost all regions was found to correlate to the calculated brittle-ductile transition, adding validity to the results achieved. We find a strong correlation between the lateral distribution of seismicity and the total strength of the lithosphere, occurring mainly in weaker zones, with crustal thickness and LAB depth highly influential.