Deformation Partitioning and Lithosphere Dynamics of Continental Orogens – DefDyCOr

The objective of this project is the integration of the P.I. Stephane Mazzotti in the host laboratory of Géosciences Montpellier, through the development of a state-of-the-art research project that will integrate the skills and technical capabilities of the P.I., his new colleagues, and international collaborators. The fundamental question addressed by the research project is: “What controls the width and partitioning of deformation and seismicity in continental orogens?”, which is one of the main challenges of modern Earth Sciences, with applications in fundamental science as well as seismic hazard assessment.

Continental orogens are mountains belts resulting from large-scale collision and accretion processes in which blocks of Earth crust and upper mantle are accreted to the margin of continental plates. Typical examples include the western USA and European Alps orogens. This project concentrates on the comparative study of two continental orogens: the Yakutat Collision in NW America and the Rif – Atlas in Morocco, in order to decipher and quantify the relative role of geological heritage (e.g., inherited weakness), large-scale body forces (e.g., topography), and local forces (e.g., slab dynamics) in the overall distribution and partitioning of deformation and seismicity. A critical impact of this research resides in the robust estimation of seismic hazard in continental plate-boundary zones. To tackle this project, we will develop innovative geodynamic models of the two target orogens. These models will be constrained by 1) velocity and strain rate fields derived from the integration of GPS, seismicity, and geology data and 2) the structure of the crust and lithosphere defined by seismic and gravity imaging. A special emphasis will be put on the uncertainties of individual datasets and final combined products.

The innovative nature of the project lies in this quantification and statistically robust integration of the multiple kinematic, dynamic, and structural datasets (GPS, seismicity, seismic imaging, gravity) with thermo-mechanical models to constrain the range of the various dynamic processes considered. This approach is first step towards the development of assimilation methods in geodynamic studies. The main originality of the proposed research is two-fold: 1/ The integration and joint analysis of multi-disciplinary techniques, combining kinematic and strain mapping, structural and dynamic characterization of the lithosphere, and lithosphere rheology, within the framework of quantitative geodynamic models; and 2/ The joint study of two distinct continental orogens to define general features and results applicable in different settings.