Movement along faults begins a few hours before large earthquakes. This is the conclusion of a study carried out by researchers from the French National Research Institute for Sustainable Development (IRD), and published in the journal Science on July 21, 2023. The study, which describes the movements recorded before large earthquakes, was carried out using data recorded by GPS stations since 2003. While current instrumental techniques are unable to detect precursory slip at the scale of an individual earthquake, this result encourages the development of more accurate instruments and denser instrumentation around faults to anticipate large earthquakes. This represents a major challenge for the Global South, where the risk of earthquakes and tsunamis is high.

In the last thirty years, earthquakes and the tsunamis they trigger have caused the deaths of nearly a million people, mainly in the Global South. Although warning systems have been put in place in some countries to limit the human and material cost of these disasters, at best these systems offer only a few seconds' warning, as they are only activated once the earthquake has begun. As yet, we are unable to predict the imminent occurrence of a major earthquake.

The idea that there is a phase preceding an earthquake is a matter of debate within the scientific community. This study shows that, on average, faults begin to slip a few hours before large seismic ruptures. By looking at displacements measured by high-precision GPS stations before large earthquakes, the scientists discovered a statistically significant precursory signal. 

Earthquakes begin, on average, with slow slip that accelerates in the hours preceding rupture. To be able to identify this signal before a particular earthquake, we would need to measure signals at least 10 times smaller than what we can presently do, or to develop dense measurement networks very close to faults. This would require significant technological progress. Despite the difficulties involved, the detailed study of slow slip on faults remains the best way to work towards to hope to, eventually, develop predictive models.


Quentin Bletery, Jean-Mathieu Nocquet
"The precursory phase of large earthquakes", Science, July 21, 2023. 
DOI : 10.1126/science.adg2565 

Research contacts

  • Quentin Bletery, geophysicist, researcher at IRD, UMR GEOAZUR (IRD/CNRS/Observatoire de la Côte-d'Azur/Université Côte d'Azur) - 
  • Jean-Mathieu Nocquet, Research Director at IRD, UMR GEOAZUR (IRD/CNRS/Observatoire de la Côte-d'Azur/Université Côte d'Azur) -

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