The project DISRUPT is a project funded for 42 months by Agence National de la Recherche, starting January 2019. The project is led by Y. Klinger at IPGP, in close collaboration with several partners from ENS, Sorbonne Université, Université Cergy-Pontoise, IRSN and IGN.

Large continental earthquakes often produce a complex surface rupture pattern, including multiple strands, jogs, or deformation along secondary faults. Such variability of the surface ruptures signs similar complexity happening at depth, where earthquake propagates along complex faults. Although surface rupture is still a primary observation for earthquakes, it has been long disregarded as not representative of deeper seismic processes. New high-resolution satellite imagery now allows quantifying surface deformation in details and brings new insights on earthquake processes. At the same time, hazard practitioners, who were mostly focused on seismic hazard, for practical reasons are now more often turning their attention to fault displacement hazard assessment, meaning assessing the probability of occurrence of surface ruptures at a given site and for a given earthquake.

The project DISRUPT addresses the physical processes controlling the occurrence of surface ruptures to be able, in fine, to test the predictive power of numerical simulation tools to be used by hazard practitioners. To do that we propose to develop new deformation measurement methodologies, to look how distributed deformation is triggered through successive earthquake cycles, to use analogue modeling to assess parameters controlling rupture morphology, and to confront all our observations with dynamic rupture simulation tools to test their capacity to predict realistic rupture patterns.

Deformation measurement methods: On one hand, we will develop methods to take advantage of the large archive of analogue historical aerial and satellite images to be correlated with modern optical satellite imagery, to increase the number of well-documented earthquake ruptures. On the other hand, we will use systematic multi-stereoscopic sub-metric image acquisition by satellites to build direct high-resolution 3D deformation maps.

Secondary deformation and earthquake cycle: Taking advantage of the well-documented 1905, M8+, Bulnay earthquake in Mongolia, using paleoseismological methods we will test if secondary ruptures are systematically activated during successive large earthquakes or if there is a magnitude threshold. The 1967, M7+, Mogod rupture (Mongolia) will offer the possibility to test the impact of preexisting geologic structures on fault growth.

Earthquake analogue modeling: We will take advantage of new materials with properties allowing for stick-slip behavior in a controlled experimental set-up to run parametric studies on parameters controlling rupture morphology.

Surface deformation simulation: We will implement two codes allowing for simulation of surface ruptures due to dynamic earthquake propagation. On one hand, we will run earthquake simulations within complex 3D fault systems to assess impact of fault geometry on surface rupture morphology. On the other hand we will run simulation where off-fault deformation can spontaneously develop as part of surface ruptures. These simulations will be both confronted to our observational datasets to assess their respective predictive power.