Giant submarine landslides (10-2000 km3) are found in the thick Quaternary sediment succession of passive continental margins. Their ages coincide with periods of sea-level fall and rise, but it is unclear how such vast failures can be triggered on low seafloor slopes (<2˚) in the absence of a triggering factor such as seismicity. Key hypotheses involve excess pore pressures linked to reductions in gas-hydrate stability, driven by changes either in climate or in subsurface fluid flow. The MEGA project wants to explore such hypotheses through the first modelling of linked changes in gas hydrate and slope stability in response to ocean pressure and temperature changes, using an innovative comparison of the Nile and Amazon deep-sea fans that experience different forms of climate forcing over glacial-interglacial timescales. As such megaslides have never triggered in historical times, MEGA will provide input for the first modelling of their tsunamogenic consequences on coastal zones.
Fluids induce earthquakes both in the form of natural swarms and when geological reservoirs are exploited. In both cases, seismicity can either stop on its own or represent the precursors of major earthquakes. For our own safety in the face of seismic risk and for the safe development of new energy sources, it is therefore necessary to anticipate the evolution of seismic swarms, which means monitoring their mechanical forcing. However, the complex interactions between fluids, slow and asismic deformations and earthquakes are complex and still poorly understood. The INSeis project is motivated by new models that reconcile these phenomena. Its aim is therefore to improve our understanding of the processes that generate seismic swarms in different contexts and on different scales, in order to improve the forecasting of swarm behaviour.
The objective of the ABYSS project is to probe the mechanical state of a fault zone prior to several large earthquakes (magnitude > 6) in order to identify systematic markers of the earthquake preparatory phase. The chosen target is one of the most active faults on Earth: the Chilean subduction zone. A promising technology will be used, the distributed acoustic measurement on optical fibers, which allows to detect earthquakes thanks to underwater telecommunication cables. ABYSS will rely on the GTD network along the Chilean coast. This unprecedented observation capability, combined with the development of real-time data stream processing, will strengthen the early warning system in Chile by improving the speed and accuracy of seismic warnings.
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