F1b: Subduction in the past & today
A full understanding of the subduction process and of its role in the Earth’s evolution requires studying the interplay between different involved physical and chemical processes with complementary contributions from different geosciences disciplines (seismology, geodynamics, tectonics, volcanology, geochemistry…).
While many of Solid Earth geoscientists are dealing with some aspects of the subduction, most of existing studies are carried out in a frame of a single discipline and complex approaches to subduction are rare.
A unique example of such a complex approach is the NSF-funded program Geo-PRISMS (Geodynamic Processes at Rifting and Subducting Margins), while similar initiatives do not exist in Europe or in France. At the same time, the institutions involved in the LabeEx UnivEarthS and in particular the IPGP regroup specialists from a large spectrum of disciplines working on the subduction, providing us with a unique opportunity to take a leadership role in this area.
Therefore, the main goal of the proposed workpackage is to develop an interaction between these different disciplinary teams and to create a group focusing on complex studies of the subduction processes.
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 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 exploits 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 implies new field observations to be collected during this project.
This project is supporting a postdoc, 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 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