In a remarkable breakthrough experiment, scientists in Switzerland have deliberately triggered around 8,000 tiny earthquakes deep beneath the Swiss Alps as part of an advanced underground research project aimed at understanding how seismic activity begins and evolves within the Earth’s crust.
The experiment was conducted at the BedrettoLab, a highly specialised underground laboratory located inside a five-kilometre tunnel system running through the Alps. Researchers from the Swiss Federal Institute of Technology in Zurich (ETH Zurich) and collaborating European institutions carried out the study under tightly controlled and fully monitored conditions, ensuring that all seismic activity remained confined deep underground and posed no risk at the surface.
According to the research team, the goal of the project—known as Fault Activation and Earthquake Rupture (FEAR-2)—was to study how stress builds up along geological fault lines and how small movements can escalate into larger seismic events. To achieve this, scientists injected large volumes of water into pre-selected rock fractures through boreholes drilled into the tunnel walls. This process altered pressure conditions underground and intentionally stimulated movement along existing fault lines.
Over a period of roughly four days, the controlled injection process resulted in approximately 8,000 micro-earthquakes. These tremors were extremely small, with magnitudes ranging from about -5 to -0.14 on the seismic scale, meaning they were far below levels that could be felt by humans or cause structural damage. However, they were still significant enough to be precisely recorded by sensitive instruments installed throughout the rock formation.
Lead researchers described the experiment as a success, noting that it produced measurable seismic activity at an unprecedented depth and scale for laboratory-controlled conditions. One of the project’s senior scientists, Domenico Giardini of ETH Zurich, highlighted that the team was able to “make the faults move” in a controlled environment, providing rare real-time insights into underground stress behaviour.
The study also revealed unexpected findings. While the team targeted a specific fault zone, seismic activity also appeared along nearby intersecting faults, suggesting that underground pressure changes can influence a wider network of geological structures than initially assumed. This has important implications for understanding natural earthquakes, as well as those triggered by human activities such as geothermal energy extraction, reservoir filling, or wastewater injection.
Researchers emphasised that the experiment was conducted safely and did not pose any danger to surrounding communities. All activities were remotely controlled from monitoring stations, and no personnel were present in the tunnel during active injection phases. Importantly, no shaking was detected at the Earth’s surface.
Beyond its scientific achievement, the experiment is expected to contribute significantly to earthquake research and risk mitigation strategies. By understanding how and why faults slip under controlled conditions, scientists hope to improve predictions of seismic hazards and develop safer methods for underground engineering projects.
The findings also underline a broader goal: learning how to better manage human interaction with the Earth’s subsurface. As underground construction, energy extraction, and geothermal projects expand worldwide, understanding induced seismicity has become increasingly critical.
Researchers believe that this experiment marks only the beginning of a new phase in earthquake science—one where scientists can no longer only observe earthquakes after they occur, but actively study their formation in controlled environments deep within the Earth.
