Mapping seismic risk
How can populations be protected in the event of an earthquake? The answer is by identifying the areas at risk by mapping the subsoil. This is one of the fields of application of the work of Inria’s Magique-3D project-team, a joint team with the applied mathematics laboratory of the University of Pau and Pays de l'Adour. The aim of this team is to better understand geophysical phenomena using 3D simulation methods. Magique-3D is the fruit of a successful collaboration between industry (Total) and public research entities (Inria, CNRS).
Watch the film "Sonder l'invisible" ["Surveying the invisible"], recently screened during the Fête de la Science and the Supercomputing trade show, to find out about our scientists’ work.
Magique-3D: Methods, software and applications
Methods and techniques
The method frequently used to represent a map of the subsoil is to recreate micro-earthquakes using real explosions. These explosions generate seismic waves which spread through the subsoil. The propagation of these waves is recorded, their behaviour reflecting the physical characteristics of the subsoil. The data recorded are combined with mathematical methods (based on the solving of “wave equations”) which allow researchers to represent an image of the subsoil in graphic form.
Through another collaboration with Princeton University in the USA, the Magique-3D researchers have developed software called SPECFEM-3D. This can be used, for example, to simulate the aftershocks that occur after an earthquake in order to locate the areas at risk of being affected. SPECFEM-3D proved its worth after the earthquake in L'Aquila in Italy on 6 April 2009. It was used to simulate the earthquake which caused the tsunami of December 2004 in Sumatra, Indonesia. By performing calculations on the entire globe, it was possible to visualise the intensity of the phenomenon and represent the propagation of the waves to the earth’s surface.
Petroleum industry and medicine
The subsoil mapping methods developed are used for oil exploration. They allow the presence of hydrocarbons to be detected even before drilling! In medical research, too, solutions are being developed to calculate bone density in order to prevent osteoporosis.