Article Dans Une Revue Journal of Geophysical Research : Solid Earth Année : 2025

Seismic Imaging of the Transition From Normal to Flat Subduction in Southern Peru by Full Waveform Inversion of Teleseismic Waves

Résumé

The high topography of the central Andes (15-28°S) is supported by thick crustal roots. The recent uplift of the Altiplano is often explained by crustal shortening and subsequent delamination of the lower crust, though its deep structure and plateau formation processes remain debated. The mechanism of flat subduction is also controversial in geodynamics. The well-documented transition from normal to flat subduction beneath southern Peru provides an ideal setting to investigate these processes. In this study, we present a new multi-parameter tomographic model of density, V P , V S , and V P / V S beneath southern Peru. The model was obtained by inverting teleseismic P and SH waveforms recorded by temporary and permanent stations across 78°W-66°W and 10°S-19°S. Time and amplitude issues in the PeruSE data set were identified and corrected before inversion. The final model shows a normally dipping oceanic lithosphere in the south, with a continuous transition to flat subduction beneath central Peru, without a slab tear. The flat subducting lithosphere appears anomalously thin and hot, likely reflecting thermal erosion associated with the formation of the Nazca Ridge. This suggests that the buoyancy of the flat slab is not due to crustal thickening and delayed eclogitization reactions, as previously hypothesized, but rather to a thermally eroded and thinned oceanic lithosphere. We also detect a thin forearc crust (14°S-19°S) overlying a thick, cold mantle wedge. The Altiplano thickening may result from squeezing the crust between this strong forearc block and the Amazonian craton. Finally, the mantle lithosphere beneath the Altiplano is abnormally thin or absent, suggesting partial removal or delamination, which could explain the regional uplift over the past 10 Ma.

Plain Language Summary

The high mountains of the central Andes are supported by an abnormally thick crust. The rise of the Altiplano, the high plateau in the Central Andes (15-28°S), is often explained by a process called delamination, where the lithospheric mantle separates from the crust and plunges into the asthenosphere. This process has been linked to a change from normal subduction (dipping angle close to 30°) to flat subduction (dipping angle lower than 10°). However, there are still active debates about the origin and structure of the Altiplano. The origin of flat subduction also remains controversial. The area beneath southern Peru, where the subduction angle changes from steep to flat, is a key region for studying these processes. This study presents new tomographic images that reveal the deep structures beneath southern Peru. We find that the flat subduction segment results from the subduction of an anomalously hot and thin oceanic lithosphere, presumably as a result of interaction with a hotspot. We also find that the lithospheric mantle beneath the South American upper plate is very thin or perhaps even absent, which may explain the uplift and support of the anomalously thick crust of the Altiplano.

Fichier principal
Vignette du fichier
jgr_25b.pdf (4.77 Mo) Télécharger le fichier

Dates et versions

hal-05344401 , version 1 (03-11-2025)

Licence

Identifiants

Citer

Li‐yu Kan, Vadim Monteiller, Anne Socquet, Hernando Tavera, Sébastien Chevrot. Seismic Imaging of the Transition From Normal to Flat Subduction in Southern Peru by Full Waveform Inversion of Teleseismic Waves. Journal of Geophysical Research : Solid Earth, 2025, 130 (10), pp.e2025JB031254. ⟨10.1029/2025jb031254⟩. ⟨hal-05344401⟩
355 Consultations
131 Téléchargements

Altmetric

Partager

  • More