Plate coupling, from seismic cycle to mountain building | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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Lithosphere tectonics and mechanics

  Plate coupling, from seismic cycle to mountain building

Plate coupling on subduction margins, from seismic cycle to mountain building and 
landscape evolution

At ocean-continent subduction interfaces, there is a fundamental partitioning between 
the mechanisms leading to elastic strain accumulation and release during megathrust earthquakes, 
and processes that lead to deformation of the upper plate generating topographic relief.
 For example, in the case of the Andean subduction, how those two processes interact is
unknown and no current geodynamic model appears to explain satisfactorily both, the generation
of the large earthquakes and the topographic relief of the Andes-Altiplano, as end products
of the subduction process. We  address this problem by focusing onto a few examples, amongst these:


 

The Carribean subduction

– The Andes in the framework of LIA Montessus de Ballore, of the Labex UnivEarthS, de l'ANR "Mega-Chile".

 

– The Caribbean
 subduction where megathrust rupture potential is unknown, and active deformation of the upper
plate needs further study.

 

– The Hellenic subduction and the Aegean,
 where the irruption of the North Anatolian Fault a few million years ago appears to have
accelerated dramatically rates of plate convergence across the subduction interface (European project Marie-Curie ALERT).

 

The San Ramon fault, paleoseismological study

Intracontinental megathrusts at the front of collisional mountain belts, associated with 
deep subduction processes, are in the same category of problem as the foregoing. For these thrust systems we address the problem of short-term mechanical coupling and segmentation,
both responsible for the location and size of large earthquake rupture. The past seismic ruptures are studied in the field using geomorphology and paleo-seismology. The link 
between mechanical coupling and the long-term evolution of the thrust system and underplating 
processes will be further studied in the perspective of recent pioneer work.

As tectonic processes of topographic build-up on subduction and thrust margins interact
 with surface processes (erosion, incision, sedimentation), we  attempt to decipher 
the tectonic versus climatic forcing contributions by an approach based on precise observations
 of landscape evolution.