What is the problem/issue being addressed?
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The quest for earthquake precursors is among the most vivid and active field of research in seismology. Still, our understanding of the preparation phase of earthquakes is quite limited and we are far from being able to detect and interpret robust, systematic early signs of a forthcoming large and damaging earthquake. As an example, in 2019, the magnitude 7.1 earthquake hit the Ridgecrest area in California and even though it was the largest in the United States in 20 years, the background seismicity preceding the mainshock didn’t show any signs of anomalous behavior. On more fundamental aspects, it is still debated if large earthquakes are predictable and would, for example, follow a process where slow fracture mechanisms would connect anomalously large sections of the fault before brutal rupture. On the contrary, some studies argue that large earthquakes are unpredictable and that their final size results from a stochastic cascade of smaller events without any previous connections between them. In the FaultScan project, we attempt to provide new insights to this problem by looking for signs indicating that large earthquakes rupturing over tens of kilometers are not the only consequence of random processes, but that they are preceded by a preparation phase that we will strive to detect.
Why is it important for society?
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After decades of progress led by fine seismicity analysis, satellite remote sensing (GPS, InSAR), and large-scale simulations, the quest for earthquake predictability has stalled. Here, we propose a disruptive approach to monitor active faults that is still in its early developments and thus capable of ground breaking discoveries. Even if this approach can only provide a small improvement in the diagnostic of a fault to produce a large earthquake, the relevance for society will be huge. Earthquakes are still among the deadliest natural disasters and mostly affect developing countries that do not have earthquake-resistant structures.
Moreover, the monitoring approach that we develop has the potential to be applied to other domains like volcano monitoring, C02 sequestration and geothermal production.
What are the overall objectives?
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The overall objective is to discover new signs of the preparation phase of earthquakes by using a groundbreaking seismic approach that relies on monitoring small stress perturbations in the vicinity of active faults. This technique uses seismic waves generated by powerful anthropogenic sources of noise like trains, car traffic or mining operations. We developed a special technique to extract seismic waves that dive deep down into fault zones at a few kilometers depth, making our approach highly sensitive to changes occurring on the fault. Apart from borehole instrumentation, this seismic approach is the only one that enables us to directly probe faults at depth.
