Impact of the Juan Fernandez Ridge on the Pampean Flat Subduction Inferred From Full Waveform Inversion

A new seismic model for crust and upper mantle of the south Central Andes is derived from full waveform inversion, covering the Pampean flat subduction and adjacent Payenia steep subduction segments. Focused crustal low-velocity anomalies indicate partial melts in the Payenia segment along the volcanic arc, whereas weaker low-velocity anomalies covering a wide zone in the Pampean segment are interpreted as remnant partial melts. Thinning and tearing of the flat Nazca slab is inferred from gaps in the slab along the inland projection of the Juan Fernandez Ridge. A high-velocity anomaly in the mantle below the flat slab is interpreted as relic Nazca slab segment, which indicates an earlier slab break-off triggered by the buoyancy of the Juan Fernandez Ridge during the flattening process. In Payenia, large-scale low-velocity anomalies atop and below the re-steepened Nazca slab are associated with the re-opening of the mantle wedge and sub-slab asthenospheric flow, respectively.

Automated summary

A new seismic model for the crust and upper mantle of the south Central Andes has been derived through full waveform inversion, covering the Pampean flat subduction and adjacent Payenia steep subduction segments. The study indicates the presence of partial melts along the volcanic arc in the Payenia segment, and suggests thinning and tearing of the flat Nazca slab. Furthermore, a high-velocity anomaly in the mantle below the flat slab is interpreted as relic Nazca slab segment, signifying an earlier slab break-off triggered by the Juan Fernandez Ridge.