Abstract of my project submitted to the ERC-STG-2017 call The ever-increasing amount of geophysical data continuously opens new perspectives on fundamental aspects of the seismogenic behavior of active faults. In this context, studying the interrelation between seismic and aseismic fault slip is essential to understand what causes and what triggers earthquakes. Despite significant advances in the last 15 years, a number of key questions still remain. How is aseismic slip related with the spatial and temporal distribution of earthquakes? Is there a unified physical mechanism explaining the occurrence of seismic and aseismic slip? The problem is that fault processes span a tremendous range of time-scales. Earthquakes propagate during seconds to minutes while inter-seismic strain accumulates for decades, centuries and even millenniums in regions of low strain rate. While different modeling strategies are used to infer seismic or aseismic slip, only a joint interpretation of inter-, co- and post-seismic datasets can allow us to fully explore the interactions between these two slip modes. The proposed work is to develop an entirely new approach, where all available datasets are assimilated to produce a unified model describing seismic and aseismic slip at all resolvable scales of the earthquake cycle. Such model will describe the evolution of inter-seismic and post-seismic slip with a resolution of a few days but also seismic ruptures propagating for tens to hundreds of seconds. In Chile, where various datasets are available, we will produce a new generation of time-dependent slip models, by jointly inverting geodetic, seismological and tsunami observations. This will allow us to address key questions on the seismogenic behavior of faults and to investigate the preparatory process of aseismic slow-slip events observed before some large megathrust earthquakes. Our time-dependent slip models will also be updated in near real time and used to automatically detect anomalous departures from steady-state inter-seismic fault slip.

The HighLand project proposes to combine seismology, remote sensing and machine learning to quantify the impact of climate on mass-wasting activity in regions of high latitude or altitude. The first objective of the project is the development of new processing chains to build, from the continuous recordings produced by regional seismological networks, instrumental catalogs of landslides. The systematic exploration of these seismological chronicles will be made possible by the use of machine learning algorithms and will enable the production of catalogs offering unparalleled spatio-temporal resolution. The seismological detection will be confronted with satellite observations with high temporal repetition possible thanks to the constellations of Sentinel and Landsat satellites. Three regions of the world will first be targeted by this new processing chain: Alaska, the Alps and Nepal. This multi-disciplinary approach will make it possible to produce the necessary observations and to build and constrain models to better understand the long and short-term links between climate and mass wasting activity. The prototype of the processing chain will serve as the basis for a system for observing and listening to the landside activity in near real time in these regions of the world and then on a global scale.

How and when the Tibetan plateau developed has long been a puzzling question with implications for the current understanding of the behavior of the continental lithosphere in convergent zones. The Central Tibetan plateau provides the ideal existing laboratory to understand the evolution of a large scale collisional orogen. Its evolution is now well constrained by an increasing amount of high quality surface and subsurface data. The integration of these data has led to the proposition of the achetypical models of orogenic evolution. Some models focus on the importance of the underthrusting of the rigid Indian and Asian plates beneath Tibet, others argue that the crust and lithosphere are weak and the thickening of the Asian lithosphere is distributed. In this project, we target Central Tibet. Although it remains the least studied part of the collision zone, it constitutes a key element for reconstructions and models involving processes such as continental subduction, underplating or extrusion to be evidenced there. We will provide detailed quantitative data on rates and mechanisms of thickening processes in central Tibet based on an integrate petrologic study of volcanic rocks and associated mantle and lower crustal xenoliths, paleomagnetic data acquired on volcanic rocks, reappraisal of available geophysical data (tomography, heat flow, Bouguer anomaly, refraction and reflection seismicity) and numerical modeling. The comparison with the geometry, lithology and evolution of the Bohemian massif will offer an overarching vision of the evolution of large scale orogens through time. These different approaches, although highly complementary, are rarely integrated within a single project to study a particular mountain belt. We propose to develop an integrated study of deep and surface processes evolution in the core of the orogen. Our aim is to focus on the Central part of the Tibet, Qiangtang Terrane and to compare it with the Moldanubian zone in the Bohemian massif as these zones correspond to the core of the orogen far away from the preserved continental subductions zones that rejunavated the initial orogenic recordings. The interest to compare the Bohemian massif with the Qiangtang Terrane is that the former offers the opportunity to observe directly in the field the root of the orogen while the second is a still active unroofed orogenic zone.

The aim of the PRISMS project is to develop a tool for modelling and predicting the effects on the Earth's ionized environment of electromagnetic emissions and particle ejection from the Sun. Through the PRISMS project, we ambition, by coupling individually validated models, to build an integrated model that will be able to propagate electromagnetic emissions from the Sun and plasma emissions from the solar wind, at the L1 Lagrange point, to the ionized space environment of Earth, with coupling functions adapted to ensure the delicate transmission at the interface between the solar wind and the terrestrial environment. This global model will be constrained by space observations, which will condition the coupling functions in order to better characterize the perturbation and its propagation. The model will evaluate the effects on the ionosphere dynamics of electromagnetic disturbances during solar flares and the effects associated with magnetic storms (corotating interaction regions and coronal mass ejections) and thereby the impact on radio communications through the propagation of electromagnetic waves in this environment. In addition, by developing a suitable module, the model will calculate the ground magnetic trace of these disturbances. At the end of the project, we will have implemented a prototype operational system that will have the ability to follow in near real-time the variations of electromagnetic solar emissions and of thje properties from the solar wind and to describe the disturbances induced by solar activity on the propagation of radio waves. This effort is part of a strategy of national independence with respect to modeling of the damaging effects of the Sun on the industrial, societal and military activities in France and more broadly on an European level.

Understanding how the environment reacts to anthropogenic or natural disturbances at short- and long-term time scales is one of the major societal and scientific challenges in the field of natural resource management and conservation. Among the wide field of the environmental challenges, this project aims to evaluate water and soil resources, related to climatic changes (rainfall regime, temperature increase) and anthropogenic actions (forest management) in medium altitude forested watersheds. For that, the project proposes a detailed understanding of the transport processes of water and its related chemical fluxes to elaborate physically based models, which should be applicable and adaptable in other climatic, ecologic and geologic environments. These models will be able to simulate and thus predict future evolution of such a natural ecosystem in response to disturbances like climate change or logging. Thus, the aim of this project are (i) to develop a methodology based on tight coupling of several geophysical, hydrological and geochemical approaches to estimate water and solute fluxes and their associate models at a watershed scale and (ii) to evaluate the methodology on the Strengbach watershed (80 ha granitic catchment in NE of France- 90% vegetation cover- Vosges Massif). Since 1986, the climatic, hydrological and geochemical parameters of this watershed have been recorded, which represents one of oldest monitored sites on granitic basement in the world. The project will be handled within four work-packages (WPs) with very strong interactions between the first three. - WP1: underground imaging and groundwater survey: Subsurface geophysics. This WP consists in combining different geophysical methods in order to build a spatial geometric image of the different depth and superficial lithological structures of the catchment. Groundwater storage will be estimated by gravimetry and RMS; - WP2: Surface/subsurface hydrology and water resources. Geophysical and geochemical approaches with biospheric and hydrologic modeling will be gathered to improve our knowledge of the hydrological functioning at the watershed scale (water storage, water pathways, water balances….); - WP3: Water/rocks/vegetation interactions. Geochemical/isotopic tracers, mineralogical and ecological data, and laboratory experiments will be used to better identify and characterize the water/rock interactions and the biogeochemical signature of soil solution, springs and stream waters. - WP4: Impact of climate change on water resources and soil mineral fertility. Calibrated models obtained through WP2 and WP3 will be used to estimate the evolution of water resources and soil mineral composition until 2100. The link between the 3 first WPs can be summary as: - WP1 will provide statistical information about the underground structure and water volume to WP2 and WP3 - WP2 will provide parameter distribution and water volumes to WP1 to assess petrophysical relationships and geophysical surveys. WP2 will also provide water pathways and travel time to WP3. - WP3 will provide constraints from the water/rock processes and therefore evaluate the reliability of the results given by WP2. The three first WPs will work inside an iterative loop between the WPs until a good match between modeling and observations is reached. Due to an EQUIPEX (CRITEX) most of the equipment required for this project is already installed and operational. The consortium is based on 7 multidisciplinary institutes, 1 foreign researcher, 1 private office, an university department for science popularization and the ONF (French forest national agency). Most of the teams involved in this project have already worked together on the Strengbach watershed but never at this level of interdisciplinarity. This project will provide a better understanding of the long-term variation of water and mineral nutrient availabilities and of forest health in middle altitude mountain areas.