As two tectonic plates drift away, the movements prior to oceanic crust formation are ill-constrained. We are convinced that the kinematic models of plate movements could be significantly enhanced by focusing on the first ten million years of divergence. During this phase of transition several problems arise. Firstly, the classical interpretations of magnetic anomalies are not trustworthy (debated geometry and/or origin of anomalies). Secondly, the movements are more complex than in oceanic domain (polyphase deformation, obliquity, asymmetry). Those particularities occur especially if plate breakup happens in magma-poor conditions (in about 50% of instances). In the Bay of Biscay, the OPEN-BAY and BREOGHAM geophysical surveys and the GALINAUTE dives samples will allow to better constrain this magma-poor transition, and thus the movement between Europe and Iberia Plates. The consequent aim is to apply the new methodologies and tested concepts worldwide.

The structure and dynamics of Earth's mantle and core are determined by the heat flux across the core-mantle boundary (CMB). The CMB heat flux pattern affects the morphologies of core convection and the generated geomagnetic field. Paleo- and archeomagnetic field models provide valuable insights into persistent features that may be controlled by the lower mantle heterogeneity, including the South Atlantic Anomaly (SAA) – a region of particularly weak intensity at Earth’s surface, where energetic particles penetrate the atmosphere thus posing severe problems to positioning systems and spacecraft electronics. Our goal is to identify persistent geomagnetic field features that will then be used to evaluate how Earth-like are dynamo models with heterogeneous outer boundary heat flux. To recover geodynamo features that are controlled by lower mantle heterogeneity, a precise knowledge of the CMB heat flux pattern is needed. Compositional and mineralogical contributions to the lateral variability of the seismic velocity in the D’’ layer distort inferences of the CMB heat flux from seismic tomography. We will infer thermal-seismic relations from mantle convection simulations in order to isolate the thermal part of the seismic anomalies. Our objective is to apply this relation to mantle tomography models in order to properly model the CMB heat flux. The most fundamental property of dynamo models is their regime, i.e. whether the generated field is dipole-dominated non-reversing or multipolar reversing. This proposal aims at establishing the necessary ingredients for each dynamo regime, taking into account the CMB heat flux pattern and amplitude of heterogeneity. Using adequate CMB heat flux models and testing the consistency of the dynamo models output with criteria derived from paleomagnetic field models, our goal is to evaluate the Earth-likeness of a large set of dynamo models with heterogeneous outer boundary heat flux.

Climate change will impact groundwater by altering precipitation patterns and increasing the demand of atmospheric evaporation demands, thereby jeopardizing the sustainability of significant freshwater reserves. Mountainous environments are particularly vulnerable to climate change, with projections indicating a decrease in groundwater recharge in several mountain regions, while reliance dependence on mountain water resources is expected to rise. However, accurately estimating the future dynamics of groundwater remains challenging. Physically-based distributed hydrological models (DHM) applied at the catchment scale are well-suited to provide reliable estimates of future changes in stored groundwater, along with their associated uncertainties. Nevertheless, modelling the influence of climate on hydrological processes in mountainous environments is particularly difficult due to insufficient monitoring and understanding of the subsurface component in these areas. A significant challenge in modelling water flow physics in such regions is defining the spatial variability of the subsurface parameters that input DHM parameters. Given the complexity of accurately representing the processes involved in groundwater dynamics, it is crucial to quantify projection uncertainties. Addressing these uncertainties requires a comprehensive understanding of their sources and a detailed analysis of the various factors contributing to projection uncertainties. CASH aims to develop a robust numerical solver for the hydrological inverse problem suitable for catchment-scale applications. This tool will incorporate conventional hydrological data and, innovatively, geophysical data, serving as (1) prior information to delineate hydrofacies geometry and probability density functions of hydraulic parameters, and (2) data directly sensitive to groundwater content and its spatio-temporal variation, which will be incorporated into the objective function. The methodological advancements will be tested and validated on synthetic catchments before being applied to a real mountainous headwater catchment: the Strengbach. There, hydrological variables have been monitored for the past 35 years, and numerous geophysical investigations have already been conducted. The pivotal innovation of CASH lies in assimilating magnetic resonance sounding and gravimetric data into catchment-scale hydrogeophysical inversion. These measurements respectively detect spatially varying water storage and heterogeneous water mass dynamics. Moreover, these data directly measure the primary variable we aim to project: the amount of water stored in the underground media. Furthermore, supplying robust a priori information along with their corresponding statistics is crucial for solving the hydrological inverse problem. In CASH, we tackle this challenge by capturing the spatial variability of hydraulic parameters through punctual geophysical measurements inversed locally. Those parameters will then be interpolated with specific geostatistical tools to produce maps of priors with the same mesh as the DHM, addressing uncertainties at the catchment scale. Until now, surface flows have often been the predicted variable of hydrological models, as groundwater prediction uncertainty is more reliant on the accuracy of hydrological model calibration. The estimation of future groundwater resource variability and its uncertainty obtained through the conditioning of the DHM with geophysical data as we will achieve in CASH appears to be unprecedented.

The project focuses on (1) the feedback between alteration and tectonic activity of active faults in the upper crust, which enhances the process of fault maturation of from chemical interactions, and (2) how this process impacts the hydromechanical properties of enhanced geothermal systems (EGS). The main research hypothesis is that fault activity induces new fractures that enhance fluid-rock interactions and associated fault zone alteration. This feedback forcing would accelerate the maturation of active faults, by creating clay gouges that weaken the fault and decrease its core permeability over time. For EGS reservoirs, when located in active tectonic zones, tectonic stresses may accelerate alteration, which clogs the created fractures and may weaken them, increasing the risk of induced seismicity during production. Our focus is on granitoid rocks, a representative lithology of the upper crust, which is also the lithology of both the Rhine Valley geothermal reservoirs and that of the wall rocks of the Nojima fault responsible for the 1995 Nanbu-Kobe earthquake in Japan. Dynamic loading pulverizes granitoid rocks, which enhances their permeability. This facilitates laboratory alteration of centimetric samples, as demonstrated by preliminary experiments. We will use core samples from the GSJ Hirabayashi scientific borehole intersecting the Nojima fault to (1) obtain a continuous alteration profile through the fault by combining core and downhole geophysical data and (2) perform flow-through laboratory alteration experiments at various differential stresses to assess the intertwined effects of tectonic loading and fault alteration.

Fluid pressure perturbations induce earthquakes at different scales, both in natural seismic swarms or during anthropogenic activities in geological reservoirs. In both contexts, seismicity may either stop on its own or be the precursor to larger, damaging earthquakes. For seismic risk mitigation and for safer energy exploitation, it is of crucial importance to anticipate the evolution of swarms. With this aim, understanding the processes at depth that trigger and drive seismicity is key, but the complex interaction between fluid pressure, aseismic deformation and earthquakes is still an open question. Motivated by recent models that conciliate fluid pressure and aseismic processes, the INSeis project aims to shed new light on the driving mechanisms of both natural and artificially induced swarms. The final goal is to propose common interpreting models in order to better anticipate swarms evolution. This project focuses on a refined analysis of seismological data from three well-instrumented sites in Europe, with different contexts and scales: (1) geothermal activities in Alsace (France), (2) natural swarms in the Corinth Gulf (Greece), and (3) in-situ experiments of induced seismicity at a decameter scale (France, Switzerland). New physical models and interpretations will be tested and validated with the support of up-to-date hydro-mechanical simulations, that compute seismicity together with the full pressure and deformation history. Finally, we will take advantage of the differences in scale, geological settings and conditions to highlight similarities in the physical processes, in order to bridge the gap in interpretations among geological objects. Finally, through statistical means, we will test and evaluate which metrics and which strategies allow for the best anticipation of the swarm behaviors.