Andes, orogène et subduction | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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Tectonique et mécanique de la lithosphère

  Andes, orogène et subduction

The Andean subduction margin : studying the generation of the largest earthquakes on Earth and the geodynamics of Andean relief building

 

Andean Orogen (Armijo et al. 2015)
Andean Orogen (Armijo et al. 2015)

The subduction zone at the western margin of South America is the living paradigm for the A-type (or Chilean-type) of subduction, which is the geodynamic system that appears to have generated the largest earthquakes and tsunamis, as well as one of the largest mountain belt - and high-plateau- systems of our planet; the Andes. At the subduction interface, there is a fundamental partitioning between mechanisms leading to these two processes. It is now clear (contrary to expectations ascribed to C. Darwin) that crustal deformation associated with any large subduction earthquake on Earth leaves no significant contribution to mountain building. The alternative idea attributing the Andean orogenic growth to large-scale accretion of intrusive bodies and volcanism is in conflict with the tectonic shortening mechanisms now admitted for explaining the orogenic relief in collision belts (Alps, Himalayas). Simply, no first-order unified theory is available for present-day orogeny occurring in our planet.

 

San Ramon Fault
The Western Andean Front (San Ramon Fault - Vargas et al. 2014)

The growth of the Andean orogen by tectonic shortening (associated with plate convergence) can now be measured over the 103-107 yr time scale, which is barely longer than the seismic cycle observed for subduction earthquakes. However, how those two fundamental processes interact is unknown and no current geodynamic model appears to explain satisfactorily both, the generation of the large earthquakes and the topographic relief generated (by some combination of accretion and tectonic shortening) as an end product of the same subduction system.

 

Andean growth and climate evolution (Armijo et al. 2015)
Andean growth and climate evolution (Armijo et al. 2015)

Our main objectives concerns :

- Plate coupling processes that eventually resume in megathrust earthquake ruptures; including tectonic complexities, at and near the plate interface, which drive segmentation.

- Geometry and kinematics of faulting at the Western Andean front; past earthquake ruptures and associated seismic hazards.

- Large-scale tectonic evolution and geodynamics of the Andean orogeny coupled with Caenozoic global climate changes.

 

Learn more on Robin Lacassin web page about Andean Orogeny

 

Our work on these topics is part and is funded by the  LABEX UnivEarthS and the ANR project MEGACHILE