Ultra-fast slab break-off at the Ionian oceanic-continental margin

Abstract

By severing the negative buoyancy of the sinking lithosphere from the surface plate and triggering regional orogenic uplift and upwelling of buoyant asthenosphere, slab detachment becomes a key driver of geodynamic processes. Here, we present a new model for the Ionian subduction that reveals a diachronous transition in slab morphology, with a coherent, steeply dipping high-velocity body in the southern sector that becomes increasingly fragmented toward the north. In the south, the slab maintains vertical continuity to depths of ∼500 km, supported by a well-defined Wadati-Benioff zone. Conversely, northern profiles exhibit a clear seismicity gap and significant reduction in high-velocity anomalies at intermediate depths, indicative of progressive slab detachment or lithospheric tearing. These observations suggest that the gravitational pull of the sinking slab has exceeded its mechanical strength during the past 1 m.y., initiating a lateral ultra-fast break-off process that zips along the subduction system north to south for a total length of at least 150 km.