Flagship Research Projects

SEISMES Vignette EPOSTThe Early POSTseismic Deformation: a Key Process in the Earthquake Cycle. From Observation to Modeling.

The main objective of the project is to better understand the complex space and time evolution of postseismic transient processes to better assess their link with the coseismic processes and how they contribute to the stress redistribution, which might lead to the generation of catastrophic seismic sequences. The originality of the project is to focus on the shorter time scale of the postseismic phase, the transition from the co- to postseismic (i.e. early postseismic, from minutes to early days) and to test to what extent the better description and knowledge of the co- and early postseismic deformation help to resolve the longer time-scale postseismic deformation (months - years).

The E-POST Young Researcher project is supported by the main French Research Funding Agency ANR over the period 2015-2019.

Fluid pressure diffusion along a strike-slip faultThe main objective is to improve our understanding of the role of fluids on the rupture of earthquake faults. To date, few data are available to study the couplings between fluids, fault slip and seismicity. In this project, we propose to develop a new in-situ approach based on the hydraulic stimulation of a small fault segment (10 m) under controlled experimental conditions.
The fluid injections will produce small fault slip (few millimeters) and will be monitored with a dense network of sensors, including pressuremeters, strainmeters, seismometers and electrical imaging. This original experiment will be conduct at 300 m-depth at the Low Noise Underground Laboratory of Rustrel in France.

OBSIVASubducting slabs carry water into the mantle and are a major gateway in the global geochemical water cycle. Fluid transport and release can be constrained with seismological data. Here we use joint active-source/local-earthquake seismic tomography to derive unprecedented constraints on multi-stage fluid release from subducting slow-spread oceanic lithosphere.

We image the low P-wave velocity crustal layer on the slab top and show that it disappears beneath 60–100 km depth, marking the depth of dehydration metamorphism and eclogitization. Clustering of seismicity at 120–160 km depth suggests that the slab’s mantle dehydrates beneath the volcanic arc, and may be the main source of fluids triggering arc magma generation. Lateral variations in seismic properties on the slab surface suggest that serpentinized peridotite exhumed in tectonized slow-spread crust near fracture zones may increase water transport to sub-arc depths.

This results in heterogeneous water release and directly impacts earthquakes generation and mantle wedge dynamics.