ISTerre seminar

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Dynamics of the Andean Subduction system : How subducting seamount chains shape Andean deformation and megathrust seismic behavior

Thursday 26 February 2026 - 11h00

Anne Socquet - ISTerre
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The subduction of oceanic ridges and seamount chains is thought to strongly influence the segmentation of megathrust faults, as well as the geometry and dynamics of subducting slabs. However, the physical processes involved remain poorly understood. Along the Andean margin, major transitions between flat and steep slab geometry coincide with the subduction of large oceanic features, making this region a natural laboratory to explore these interactions. In this seminar, I will present results from the ERC DEEPtrigger project, based on dense seismological and geodetic observations from southern Peru and the Atacama region of Chile. By combining seismic tomography, earthquake catalogs, satellite geodesy (GNSS) and SAR interferometry, we image plate structure and geometry, deformation of the upper plate, the distribution of slow and fast earthquakes, and potential fluid pathways. These complementary datasets allow us to address several key questions: Can ridge subduction sustain flat slabs? How is deformation transferred from the megathrust to the upper plate? Does slab steepening involve slab tearing? And how do subducted bathymetric features influence megathrust coupling and the balance between slow slip and seismic rupture? I will illustrate these processes using selected examples from the Peru–Chile subduction zone, focusing on the regions where the Nazca and Copiapó ridges enter the subduction zone.

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Organizing team : Organisation labo

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères