Description du projet
Un examen approfondi des fractures rocheuses avant et pendant les tremblements de terre
La capacité de prédire avec précision le moment, le lieu et la magnitude des futurs tremblements de terre reste limitée. Aujourd’hui, le projet BREAK, financé par le CER, fait trembler le monde de la mécanique des tremblements de terre. Il permettra de déterminer si la déformation de la croûte terrestre se localise sur des failles qui peuvent soit se rompre rapidement en produisant des tremblements de terre, soit subir un lent glissement asismique. Plus précisément, il fournira les premières observations quantitatives en laboratoire du champ de déplacement complet dans les roches avant et pendant le glissement de la faille et en séparera les composantes asismiques et sismiques. Le projet développera de nouvelles techniques expérimentales basées principalement sur l’imagerie dynamique simultanée par microtomographie à rayons X synchrotron et l’acquisition et l’analyse de données d’émission acoustique.
Objectif
Deformation in Earth’s crust localizes onto faults that may rupture rapidly producing earthquakes or undergo slow aseismic slip. The detailed mechanisms that control the transition between the seismic and aseismic regimes and the onset of earthquakes remain unknown. These mechanisms control the geophysical processes preceding catastrophic failure, such as fracture development and strain localization on faults and in the rock volumes surrounding them. Our goal is to provide the first quantitative laboratory observations of the full displacement field in rocks before and during fault slip, and separate the aseismic and seismic components of it. We will develop novel experimental techniques based primarily on simultaneous dynamic synchrotron X-ray microtomography imaging and acoustic emission data acquisition and analysis. The data will reveal how slow and fast deformations develop and interact with each other in dry and wet crustal rocks under the stress, fluid pressure and temperature conditions at depths up to 10 km, and characterize the production of fractures during earthquake nucleation and rupture propagation. We will search for weak signals before dynamic rupture and develop ways to predict the time to failure from these signals. If we can demonstrate that the joint analysis of acoustic emission signals and X-ray microtomography data can be used to predict dynamic rupture in our experiments, we will have discovered an important lead towards earthquake prediction, which we will pursue in follow-up projects. We will compare the deformation microstructures produced in laboratory experiments with those of natural rock samples collected in California and Norway, where earthquakes occurred. The overarching goal is to progress toward a general model of the path to brittle failure in rocks by advancing knowledge of how fractures accumulate before and during both slow and fast earthquakes, under dry conditions and in the presence of water.
Champ scientifique
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ERC-ADG - Advanced GrantInstitution d’accueil
0313 Oslo
Norvège