News

Injection operations started on Wednesday afternoon, 22 April. During the following night, the experiment was temporarily interrupted due to an unexpected  power outage. After repair work was completed, injection was resumed on Thursday, 23 April in the late afternoon. The simultaneous injections via two stimulation intervals in two separate boreholes led to the activation of several structures across the heavily instrumented experimental volume.  

The experiment was stopped on Saturday morning at 08:30, after a total of 750 m³ of water had been injected over approximately 50 hours of pump operation. A few thousand very small seismic events were induced, with local magnitudes ranging from −5 to −0.14. While some seismic events occurred on the target fault zone, a large number of events took place on neighbouring geological structures activated by the fluid injection. The decision to stop the experiment was taken when an increasing number of seismic events occurred outside of the core measurement network, limiting their scientific analysis.  

Overall, the experiment confirmed that faults can be activated at the BedrettoLabs' Earthquake Physics Testbed, and that resulting seismicity remains within the expected range. The ground shaking produced outside the tunnel was 5’000 to 6’000 times below the design ground acceleration value from the Swiss Norms, with peak ground acceleration values of 0.000014g at the tunnel entrance, 0.0000167g at the top of the mountain, and 0.0000172g at the Furka Base Tunnel entrance. These values are approximately 700 times below the level associated with perceptible and approximately 7’000 times below levels associated with damaging earthquakes. 

The research team has begun a first analysis of the collected data, which will inform the preparation of the next FEAR-2 experiment planned for June or September.