Investigating continental lithospheric dripping and deformation-constraints from multi-parameter seismic models

This study utilizes high-resolution multi-parameter full-waveform inversion (FWI) models to investigate the structure, evolution, and destabilization mechanisms of the continental lithosphere beneath North America and Europe. The results reveal the widespread presence of vertically oriented high-velocity anomalies extending from the base of the lithosphere into the mantle transition zone beneath stable cratons. Combined with geodynamic modeling, these features are interpreted as signatures of lithospheric dripping or delamination processes driven by large-scale mantle flow associated with subducted slabs. This suggests that even long-lived, stable cratonic roots can undergo passive erosion and removal under specific mantle flow conditions.

Detailed analysis of shear-wave velocity profiles and seismic anisotropy further reveals a depth-dependent strength stratification within the lithosphere. In oceanic regions, a low-velocity, weak asthenospheric layer appears between ~70–200 km depth, whereas in cratonic regions, velocities remain significantly higher than reference models (e.g., STW105) down to ~250 km, indicating a cold and rigid lithospheric root. Anisotropy profiles show contrasting deformation behaviors: oceanic lithosphere exhibits weak anisotropy at shallow levels but stronger anisotropy at depth, reflecting active mantle flow beneath a brittle lid; in contrast, cratonic regions show relatively weak anisotropy overall but enhanced signals in the lower crust, possibly due to fossil deformation fabrics.These findings support a “sandwich-like” strength model of the lithosphere, characterized by alternating brittle and ductile layers. The presence of lower-crustal anisotropy suggests significant viscous flow, while upper mantle anisotropy indicates alignment with mantle flow patterns. Similar features are observed in North America, including strong azimuthal anisotropy in both the lower crust and around 100 km depth beneath the craton, further supporting the existence of vertically distributed, rheologically distinct domains.

Overall, this work provides important seismic constraints on the internal structure and dynamics of continental lithosphere. It demonstrates that cratonic lithosphere is not universally stable and can undergo modification through deep mantle processes. It also clarifies the nature of strength layering, deformation mechanisms, and interactions between tectonically active zones and stable lithospheric domains—key insights for understanding continental evolution and intraplate seismicity.