Faulting, from observations to fracture mechanics | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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Research Departments

Lithosphere tectonics and mechanics

  Faulting, from observations to fracture mechanics

Geometry, propagation, dynamics of faulting, from observations to fracture mechanics

Fracture mechanics

Earthquake surface ruptures, paleo-earthquake time series, as well as geometry,
 growth and propagation of active faults have long been major points of interest of our lab. We now explore in more depth the factors that control the geometry 
and kinematics of fault systems, growing from their initiation to the organization of large scale
 structures. One important focus is the reciprocal interactions between successive 
earthquakes and the evolution of fault geometry; for example, how dynamic rupture affects 
fault geometry through damage or branching, or how fault geometry may control earthquake
 rupture and the occurrence of earthquake sequences.

High-resolution maps of the surface fault traces obtained by combining field observations 
and satellite imagery reveal the geometric complexity of rupture. Detailed earthquake source imaging suggests that such complexity is not only an effect of the free surface, but that 
it also exists at depth. Recent work has shown that if the dataset becomes large enough, one
 can start to identify generic properties for fault systems that should be of use in further modeling 
efforts. We aim to develop a dataset of detailed field observations, 
including earthquake rupture geometry and time series of past earthquakes, that will be implemented 
in a set of models describing the nucleation of faults and their temporal geometric
evolution at different scales of space and time.
 
We use the new possibilities from the submetric optical satellite images, as well as
 high resolution topographic data acquired from these images, field photogrammetry or Lidar
 techniques, to accurately map fault and rupture geometry. When possible, the slip distributions is determined and field-work is conducted to cross-check key observations 
against the images and to establish earthquake time series using paleo-seismology. In the 
near future, the rapid repetition of image acquisitions and geodetic techniques, based on In-
SAR and image correlations, as well as seismic activity monitoring, will allow to dynamically 
map the evolution of elastic and permanent strains on active faults, which are in some case 
coeval with magma intrusion like in the Afar. Besides, key geological observations and dating
 of markers is used to constrain how faults have evolved and propagated at larger times cales,
 then to constrain mechanical models of fault growth and interaction at crustal / lithospheric
 scale.