Imaging Slab Detachment Within the Western Hellenic Subduction Zone

Abstract

AbstractThe Western Hellenic Subduction Zone (WHSZ) has been the focus of numerous seismic investigations, but its structure, particularly between ~150‐ and 250‐km depth, remains poorly understood. Many questions exist regarding the slab geometry at these intermediate depths, including whether the slab displays any tears related to tectonic processes along the WHSZ; however, local and regional studies only provide limited depth coverage, and the coarser resolution associated with broader‐scale investigations makes it difficult to discern detailed slab structure. Here, we have employed an adaptively parameterized inversion scheme to develop a new P wave tomography model for the WHSZ that bridges the gap between regional‐ and broader‐scale studies. Our new model highlights a trench‐parallel tear in the subducting lithosphere between northern Greece and the Gulf of Corinth. Further south, the imaged velocity structure indicates that the slab is retreating to the west and that it is thinned by the southward propagating tear, but the slab has not yet detached in this area. The tear well correlates with the down‐dip limit of seismicity in central Greece, while the steeply dipping slab between ~60‐ and 200‐km depth beneath southern Greece coincides with a steeper and deeper Wadati‐Benioff zone. While the slab continues into the lower mantle, earthquakes terminate at ~200‐km depth, and this is best attributed to dehydration processes in the subducting lithosphere. The southern extent of the tear imaged in our study also coincides with volcanic centers in eastern Peloponnese. Our results suggest that the trench‐parallel tear strongly influences seismicity and volcanism throughout Greece.