F1b: Subduction in the past & today
The description and understanding of the dynamics of the solid Earth, as well as its interactions with the hydrosphere and the biosphere, requires quantitative constraints on the processes at work. The theory of plate tectonics, the principles of geochemical dynamics applied to tracking of surface and deep Earth processes, as well as pioneers studies of bio-mineral interactions are examples of achievements obtained at IPGP during the last decades. However, as good as the understanding of present solid and surface Earth dynamics is, its initiation during the early ages of the Earth remains poorly constrained and understood. To fill the gap between the present and pristine dynamics of the Earth, specific sub-projects linked to the exploration of the proto-Earth and to the study of modern analogues will be developed conjointly. During the first two years of Frontier Project 1, effort will be devoted at 1) performing a new drilling operation of a key stratigraphic succession of the Archaen Eon and 2) constraining the rates and regimes of deformation over a range of spatial scales along the Chiliean Margin.
Active deformation and earthquake activity along the Andean subduction zone in Chile
Coordinators: R. Armijo (IPG Paris, France), R. Lacassin (IPG Paris), N. Shapiro (IPG Paris), J.P. Vilotte (IPG Paris)
International collaborations: Universidad de Chile (J. Campos and G. Vargas), Universidad Católica del Norte (G. Gonzalez), GeoForschungsZentrum (GFZ) Potsdam (O. Oncken), University Potsdam (M. Strecker)
The Andean subduction zone in Chile, associated with the fast convergence of the Nazca plate beneath the South American plate, is one of the most active in the world as attested by the Andes, the largest mountain belt – and high plateau – systems of our living planet, and by the associated seismic activity with four mega earthquakes and tsunamis in the last 120 years. Scientific questions today are related to the understanding of the transient and permanent deformation processes, their variations and interactions, along the Chilean subduction zone, that lead to the occurrence of large subduction earthquakes and tsunamis, and to the building of the Andes. A critical step, of important augmented economic and societal implications, is to integrate these different spatial and temporal scales within a geodynamic model.
The Andean subduction zone in Chile and the associated large subduction earthquakes: the earthquakes rupture area is indicated by the size of the ellipses; and the mean rate and direction of the convergence between the Nazca and the South American plate is indicated by the arrow. The main barriers associated to the segmentation the subduction zone are pointed in this map
To address these questions, innovative data analysis and data modelling methods are required to exploit the massive data generated by the detailed tectonic and paleo-seismology field studies, the high-resolution observation systems integrating geodesy and seismology monitoring networks operated by the International Associated Laboratory Montessus de Ballore (https://www.lia-mb.net), the French-Chilean initiative between the CNRS-INSU and the Universidad de Chile (Santiago), in which IPGP is one of the main partners, and by the spatial observation systems (InSAR).
The first objectives are :
- Detailed analysis of the February 27, 2010 offshore Maule (Mw 8.6, Central Chile) earthquake, in terms of the rupture process, associated crustal deformation and crustal property changes, of its implication in term of the seismic hazard in the northern part of Central Chile – in particular the Valparaiso region. This analysis will exploit the extensive seismological (at regional and global scales), geodetic and geological data that are today available with unprecedented accuracy, before, during and after the event. Lessons to be learned from the offshore Maule earthquake will have important implication and applications for further study of the seismic hazard in northern Chile.
- Study of the permanent deformation, associated to the growth of the Andean orogeny by tectonic shortening, measured over the 103-107 yr time scale, which is barely longer than the seismic cycle for subduction earthquakes. We want to characterise the evolution of the west-vergent geological structures in relation with the subduction processes and to construct a mechanical model involving tectonic accretion at the subduction interface consistent with the tectonic and morphological evolution of the Central Andes and the Altiplano. This will imply new field observations that will be collected during this project.
This project is supporting a 1-year postdoc, attributed to Natalia Poiata, and a number of tectonic field studies, sampling and dating.
Position Name Laboratory Grade, employer WP leader Nikolai Shapiro IPGP DR CNRS WP member Anne Le Friant IPGP DR CNRS, WP member Nathalie Feuillet IPGP Physicienne , IPGP WP member Guyard Hervé IPGP Post-Doc WP member Seibert Chloé IPGP PhD/IPGP WP member Pierre Agrinier IPGP Professor, IPGP WP member Alberto Roman IPGP Post-Doc WP member William Frank IPGP Post-Doc WP member Jean Soubestre IPGP Post-Doc WP member Léonard Seydoux IPGP PhD/IPGP WP member Kairly Jaxybulatov IPGP PhD/IPGP WP member Sergey Abramenkov IPGP PhD/IPGP
2016 Milestones :
- Work in two target regions: the Lesser Antilles and the Kamchatka subduction zones.
- Analyzed and interpreted previously collected data and performed new field experiments.
- Worked on the analysis of geophysical data from other subduction zones (Mexico, Indonesia) that contribute to understanding of active seismogenic and volcanic processes.
- This work resulted in several publications and presentations at international scientific meetings.
- The support from Labex also helped to obtain other funding, used to extend the study of the subduction zone dynamics in the two target regions.
- The expertise developed by the team in the Lesser Antilles thanks to the support of the Labex program WP F1-2 allows for developing a new research program on the Ryukyu subduction zone in Japan in collaboration with colleagues of the TOKYO University and the Earthquake Research Institute.