A tunnel parallel to a natural fault has just been constructed in the BedrettoLab underground laboratory at ETH Zurich, in the Swiss Alps, with the aim of studying how earthquakes originate, propagate, and stop. This new "window" for close-up study of earthquakes will enable the development of a unique infrastructure, with the installation of cutting-edge observation systems.
Il ETH Zurich (ETH) he built a new one 120-meter long tunnel at his BedrettoLab, an underground research laboratory located in the Canton of Ticino (Switzerland). The new tunnel is developed in parallel to a carefully selected natural fault zone to conduct the experiments envisaged by the FEAR project (Fault Activation and Earthquake Rupture), funded by the European Research Council (ERC, within the Synergy projects) with 14 million euros and aimed at providing an answer to two of the most important and still unsolved questions in seismology: What happens just before an earthquake starts? And what causes it to stop?
Thanks to the proximity of the tunnel to the selected fault, researchers will be able to study in detail how an earthquake forms at a specific point on a fault and how it propagates along it until it exhausts its energyUsing innovative observation systems and installing different types of sensors, the FEAR project research group, which includes ETH Zurich and the National Institute of Geophysics and Volcanology in Rome (INGV) e the University of Aachen (Germany), is studying how faults move to better understand earthquakes and the processes that generate seismic waves responsible for ground shaking during a seismic event, with the hope of expanding the limits of earthquake predictability.
To this end, the international research group created by the FEAR project has developed numerous collaborations with other universities in Switzerland, Italy, Germany, France and the USA.
A one-of-a-kind observatory at a fault line
The FEAR team has drilled numerous wells to reach the fault, install observation systems, and study the earthquakes at their source. Many of these wells allow us to monitor processes within the rock volume surrounding the fault; others serve to inject water used to trigger small earthquakesEquipped with a wide range of sensors, these wells form a cutting-edge monitoring network, unique in the world placed directly on the selected fault.
The sensors present there have a sensitivity adequate to detect small movements generated by seismic events of magnitude -5 (a value negative of the Richter magnitude) and will measure fundamental parameters such as fluid pressure in fractures and variations in deformations.
During the large-scale simulation experiments being prepared by the FEAR team, hundreds of cubic meters of high-pressure water will be injected into the fault zone. The resulting increase in fluid pressure reduces the resistance (friction) on the fault planes, weakening them and facilitating their slippage. This reduction in friction can trigger fault movement and, consequently, an earthquake.
"The fault observatory is the missing piece of the earthquake study puzzle.", declares Prof. Domenico Giardini, one of the four coordinators of the FEAR project. We have excellent monitoring networks around the world. However, most of them are located on the surface, and therefore many kilometers away from the earthquakes' origin. Furthermore, even the few sensors in the wells are typically located only near fault zones, not inside them..
Trigger a magnitude 1 earthquake
In the next experiments the FEAR research group intends to generate an earthquake of magnitude 1.: a value well below the threshold of human perception (which is around a magnitude of 2.5 on the surface), but still capable of producing strong ground movements a few meters from the fault.
Researchers can draw on the extensive experience they have gained over the past four years from numerous injection experiments conducted at the BedrettoLab with increasing pressure levels, which have so far induced earthquakes up to a magnitude of -0.5.
The dense network of sensors placed on the fault zone and in the surrounding area It will help researchers understand what happens before, during, and after such an event. and, furthermore, it will also allow them to search for precursor signals, which may be impossible to detect with less sensitive monitoring systems and which, in the future, could help predict the strongest earthquakes.
Useful links:
National Institute of Geophysics and Volcanology (INGV)
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