Persistent earthquake-rupture segmentation due to variable interseismic slip accumulation within the southern Hellenic subduction plate-interface zone in Greece

Increasing evidence suggests that large thrust-faults that splay from the plate-interface to extend within the upper-plate have a significant impact on subduction seismogenesis. The manner in which these two elements, the plate-interface itself and its splay-thrust faults, interact with one another during the earthquake cycle remains, however, poorly explored. Here, we use GPS velocities, constrained by millennial fault slip-rates, to quantify the accumulation (and partitioning) of strain on individual faults of the plate-interface zone and capture their possible interactions. We zoom into the southern Hellenic Subduction System (HSS), where the greatest (M8.3) earthquake and tsunami ever recorded in the Mediterranean was produced by slip on a splay-thrust fault. Our analysis shows that the HSS is kinematically segmented and strain is accumulated at spatially variable rates along individual structures of the plate-interface zone. We find that insterseismic locking reaches up to ~85% and ~45% on the western and eastern segments, respectively, and on structures different to those that ruptured historically. Although the western HSS has been more active recently (e.g. 365 BC), the eastern HSS carries currently higher potential for large-magnitude (M>6) earthquakes andits interface-zone appears to be closer to failure. Elastic fault-interactions are responsible for both significant inter-segment variability in strain-accumulation and millennial uniformity in earthquake rupture-segmentation between eastern and western HSS.