The federation
Intranet
CENTURISK project : Novel method to identify the faults prone to break
***A novel method to identify the faults prone to break in the coming century, hence posing the most immediate risk.
Coordinator : I. Manighetti, ANR RiskNat acceptée 2009.
ISTerre team involved :
- Cycle sismique et déformations transitoires
- Risques
- Ondes et structures
National collaborations with
– Géosciences Azur
– Géosciences Montpellier
– Laboratoire de modélisation et d’imagerie en géosciences de Pau
– CEREGE, Aix-en-Provence)]
Our continents are cut by thousands of active faults that potentially threaten us. Can we identify among these faults those most likely to produce a strong earthquake in our lifetime, that is, in the next century ? These vulnerabilities, ready to break, are the ones from which it is most urgent to protect oneself.
Part of the answer lies in our knowledge of the strong earthquakes that have occurred on the faults. If we knew where, when and how a fault has broken over the past thousands of years (10-20 earthquakes), we could construct the empirical curve describing the frequency of occurrence of large earthquakes on this fault. This curve would indicate whether the fault is currently in a phase of paroxysmal seismic activity (4-5 strong earthquakes over a period of time <100-200 years), -in which case it is highly likely to break during our century -, or on the contrary in a rather quiescent phase (1 strong earthquake every 100 years), - in which case its break is unlikely to affect us immediately. At present, no technique can trace the last 10-20 major earthquakes on a fault.
We are therefore developing a new approach that can carry out such recognition. We suggest that the memory of most of the strong continental earthquakes is now buried in the first 10 m of the ground. We combine 3 recent geophysical tools (3D GPR, electric, high resolution seismic) to explore the first 10 m of ground along target faults chosen for their optimal chances of success. We hope to identify the trace of the last 10-20 earthquakes on these faults, and measure the displacements produced, thus estimating their magnitude. Coupled with the dating of the identified earthquakes, this work should make it possible to construct the desired empirical curves and thus identify the faults whose rupture is to be feared during our century.