Very dense seismic networks, consisting of thousands of geophones, are common in the subsurface exploration industry. They allow very detailed imaging of the underground through active or passive seismic methods and have been used to monitor and optimize the development of reservoirs in particular in the oil-and-gas industry through the recording of micro/nano seismicity induced during fluid injections. However, these seismic networks are designed to be installed for a limited amount of time, from a few days to a few weeks, and represent a major investment that is generally unaffordable outside the oil-and-gas industry. By contrast, permanent/long-term monitoring networks are usually restricted to a very few numbers of sensors. This limits, or even precludes, the complete characterization of seismic events (precise location, focal mechanism, source time function, etc.), detailed analysis of repeating events (a signature of aseismic deformation), and 4D imaging from micro-seismicity or ambient seismic noise. These networks are not adequate for reservoir management, which requires detailed information about reservoir structure and dynamics. The PrESENCE project presents and tests a new paradigm of collaborative monitoring of geohazards in urban environments: we will obtain seismological observations using a large number of low cost internet-connected equipment together with strong involvement of local public authorities and citizens. The PrESENCE project focuses on seismic hazards induced by deep geothermal operations and their associated societal perception. This topic is becoming a major issue in the development of renewable energies that involve the subsurface as seismic hazards are of significant public concern and can have major socio-economic impacts. The PrESENCE project is based on our rich experience from the recent seismic crisis in Strasbourg, which culminated in the paroxysmal Dec 4, 2020 M3.6 earthquake that led to the closure of the deep geothermal energy Geoven site (Fonroche-Geothermie company). The breakthrough strategy at the heart of the PrESENCE project relies on the deployment of Dense Semi-permanent Seismic Networks (DSSN) using low-cost seismic stations installed in internet-connected buildings and operated by non-seismologists. This new network concept goes beyond the historical choice between sparse permanent networks and very dense but temporary networks that cannot facilitate long-term monitoring. DSSNs represent an opportunity for traditional seismic network operators (public research institutes or private companies) to benefit from a vast amount of complementary data. The PrESENCE project will characterize the impacts of this new network concept on operational seismic monitoring, subsurface imaging, temporal monitoring of subsurface properties, warning systems, and the estimation of sociological impacts on the perception of seismic risk. The main questions we will tackle are: What are the intrinsic technical performance, limitations and complexity of these low-cost systems in terms of scientific requirements? How do such systems compare to classic and emerging seismic wave field measurement technologies? What scientific contributions can we expect from local or regional-scale DSSN in terms of knowledge of sub-surface reservoirs, their dynamics and the assessment of related hazards? How can DSSN data and products be integrated and used to improve the efficiency of reservoir monitoring? What are the impacts of public commitment in scientific research through the operation of a seismic station, on the public perception and representation of seismology and related scientific and industrial activities?

Understanding how solid materials break is a major issue, with challenging physics. Slow loading leads to creep or catastrophic rupture. Despite the major risks, no physics-based model predicts Earthquakes, and engineered structures require high safety margins. These difficulties are linked to heterogeneities and thermal vibrations. The physics of fracture concentrates energy stored at a large scale, to dissipate it locally around the fracture tip, which can lead to significant heating. We will analyse the mechanical behaviour, the associated energy flux, the heat source and transport, temperature and stress around the crack tip, and the ruptures of molecular bonds. We will compare numerics to experiments, breaking different materials (polymers, glass, elastomers) with detailed local temperature measurements. This will allow testing and extending the theory and its predictive character. The temperature around crack tips will be measured by several techniques, at different spatial and temporal scales. These measurements will be compared to the theoretical computations. We will also explore different types of heterogeneities and material heat conduction to analyse the mechanical impact. This has ambitious applications, such as the design of high-performance materials.

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.

The role of forest ecosystems in the current global ecological crisis is critical, yet we are far from understanding the full range of factors that affect forest nutrition and that condition their ability to act and respond to climate. The ecosystem services provided by forests are limited by the water and nutrient stresses that threaten them. While the cycles of water, carbon, nitrogen and phosphorus have been and are being studied extensively, not enough attention has been paid to the essential mineral nutrients whose ultimate origin can only be rock weathering. This project aims to improve our knowledge of mineral nutrition processes in trees, and in particular to disentangle the part of mineral nutrients that comes from biological recycling by the plant itself from that which comes from external inputs such as mineral weathering or atmospheric deposition. This distinction between external inputs and internal recycling is crucial to improve current ecophysiological numerical models. To do so, we propose to use boron isotopes that have recently proven their potential to distinguish sources and processes affecting mineral nutrients. We base the project on a scaled approach ranging from controlled experiments in ECOTRONS to the watershed. The project relies on the use of community infrastructures such as ANAEE, OZCAR, ICOS or Renecofor that provide experimental sites to explore environmental gradients and on an exceptional instrumented Eucalyptus plantation in Brazil. The originality of this project lies in its scientific consortium because the communities that build ecophysciological models and those that study and model chemical alteration are not enough working together. The project is part of the critical zone study perspective, an attempt to reconnect the disciplines.

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.