News Archive - 2025

What’s the reason you want to do research in such a remote place like the BedrettoLab?

The physics laboratory we want to establish in the BedrettoLab is an extension of our own labs. One of the key challenges we face in particle physics is radioactivity coming from the atmosphere. You have to imagine that there is a constant rain of muons, particles that are part of cosmic radiation, permeating everything: our bodies, buildings, equipment. Muons can interact with materials and create background radiation through various secondary effects, such as spallation or neutron production. When you search for dark matter, the instruments you use are extremely sensitive to this kind of radiation. Therefore, you need to find places that shield you from it. That’s the main reason why much of our research and development happens in underground facilities, not just the experiments themselves, but also the building and testing of our instruments.
The BedrettoLab is perfect for this. It’s just a two hours journey from Zurich and therefore easily accessible. With around 1.5 km of granite above us, we’re shielded from most cosmic radiation. Plus, the lab is already well-equipped, which gives us a great starting point.

One of your major research topics is dark matter. Can you briefly explain what dark matter actually is?

What we know from astronomical and astrophysical observations is that there’s about five times more matter in the universe than we can actually see. That means most of the matter in the universe is invisible, we can’t see or touch it, but we know it’s there because of how its gravity affects stars and galaxies.
The behavior of dark matter suggests it should be a new kind of particle, but we haven’t directly detected it yet. And we don’t yet know its mass.
What we’re hoping to detect with our instruments is a collision between a dark matter particle and regular matter. Such a collision would produce a tiny flash of light and/or charge that our special detectors could measure.

Do you expect to detect such a collision once your equipment is set up in the BedrettoLab?

Detecting such a collision there is unlikely, simply because it would require very large particle detectors. What we plan to do in the BedrettoLab is to develop new techniques that we’ll later use in larger detectors and to perform measurements shielded from cosmic rays that helps us to improve our detectors. That said, our long-term vision for the BedrettoLab does include equipment that could, in principle, detect particles such as dark matter.

Can you explain your plans for developing fundamental physics research in the BedrettoLab?

We’ve already started our first measurements in the BedrettoLab to understand the environment there in terms of fundamental physics. This includes detecting radiation fields, electromagnetic interference, and vibrations. For the vibrations, we’re using data from the seismological instruments already in place.
The next step is to build a cleanroom in the cavern at tunnel meter 3,500. This cleanroom will open up several possibilities for experiments in fundamental physics. In the first phase, we’ll install a high-purity radiation counter to measure and screen materials for use in dark matter and neutrino detectors, perform precise isotope analysis, and that also can be used to examine the radioactive content of soil and water samples.
Later on, we’d like to add a dilution refrigerator. This device would allow us to detect potentially  dark matter even without large-scale equipment. It operates at temperatures close to absolute zero and is thus able to operate ultra-sensitive quantum sensors, which can detect tiny signals from rare particles.
A dilution refrigerator like this is rare in underground laboratories, so that would be quite special. Overall, I’m really impressed with the BedrettoLab and very optimistic about building a unique laboratory for fundamental physics there.

More info about Björn Penning's research at the BedrettoLab can be found here.

ETH Zurich has constructed a 120-meter-long side tunnel at the BedrettoLab, an underground research facility in Ticino (Switzerland). This new tunnel runs parallel to a carefully selected natural fault zone. Thanks to this specific location, researchers can study in detail how an earthquake starts at one point along a fault and then propagates until it runs out of energy. Using specialized equipment, an European research consortium is studying how faults move to better understand – and potentially predict – earthquakes. The project behind this initiative, called Fault Activation and Earthquake Rupture (FEAR), was funded by the European Research Council with €14 million. It aims to answer two of the most fundamental and unresolved questions in seismology: What happens just before an earthquake begins, and what causes it to stop. Researchers hope that answering these questions will help push the boundaries of earthquake predictability.

A unique on-fault observatory

To study earthquakes right at their source, the FEAR team drilled numerous boreholes. Most of them to monitor processes in the rock. Others to inject water and induce small earthquakes. They are equipped with a wide range of sensors and together form a novel on-fault monitoring network. The sensors are sensitive enough to detect earthquakes as small as magnitude -5 and will also measure other parameters such as fluid pressure in fractures, stress changes, and more. During the large-scale stimulation experiments the team is now preparing, hundreds of cubic meters of water are injected into the fault zone at high pressure. Fluid overpressure reduces the existing stress on fault planes, weakening them and making it easier for them to slip. This reduction in friction can trigger fault movement, resulting in induced earthquakes.

“An on-fault observatory is the missing piece of the puzzle in studying earthquakes”, says Prof. Domenico Giardini, one of the four principal investigators of the FEAR project. “We have excellent monitoring networks around the world. However, most are placed on the surface and are therefore located several kilometers away from the earthquake's point of origin. And even the few sensors placed in boreholes are usually only near fault zones, not directly within them.”

Triggering a magnitude 1 earthquake

In their upcoming experiments, the research team intends to induce a magnitude 1 earthquake. That is typically well below the threshold of human perception, which is around magnitude 2.5 at the surface. However, within meters of a fault, the resulting ground motions can be strong. The FEAR researchers build on extensive experience from the past 4 years, having conducted numerous injection experiments in the BedrettoLab, with increasing levels of injection pressure, and so far triggering earthquakes up to a magnitude of -0.5. The dense network of sensors, placed both on and around the target fault zone, will help the researchers understand what happens before, during, and after such an event. The researchers will also look for diagnostic precursory signals, which may not be detectable with less sensitive monitoring setups, and which could one day help predict large earthquakes. 

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The injection began on 2 June and lasted for two weeks, during which 240 m³ of cold water were injected. The borehole will remain closed until early August. The test provides valuable data on the hydraulic response of the rock mass to long-term injection.
During the injection, researchers observed a relatively low level of seismic activity compared to previous high-pressure injection tests conducted for geothermal research. Nevertheless, the seismicity cloud offers insights into pressure propagation and the creation of new flow paths through the rock. The injection was accompanied by innovative noble gas tracers, which help track the fate of the water within the fracture network.
After the borehole is reopened at the beginning of August and several weeks of outflow have taken place, the next phase of the experiment will begin. This time, hot water will be injected following the same procedure as during the cold-water injection.

The concept being investigated in BEACH is already established in sedimentary rocks and commercially available. Larger buildings, such as the German Bundestag building, use such underground storage facilities for heating in winter. By combining several boreholes, the system can also be used for cooling in summer. The predominant bedrock in Switzerland, which makes up about 60% of the country's surface area, consists of crystalline rock. Unlike sedimentary rock, it lacks the pore space that provides the storage effect. However, the opportunity offered by crystalline rock lies in the fine fissures that could be used to store water and heat.

Such a process has not yet been tested in this type of rock. In preparation, researchers have already created numerical models based on data collected in previous experiments at the BedrettoLab on rock volume. In the now running test, water is being injected into the borehole to heat it in the surrounding rock. Initially, the water will remain in the rock for only a few days, but in further experiments within the BEACH project, it will be left for longer periods, and warm water will also be injected to test heat storage.

Storing heat in rock

In a real-life project, excess heat in summer, e.g. from solar energy, would be used to heat water, which would then be stored in deep rock. Depths of around 1.5 km are planned, where the average temperature is around 60 °C. Depending on the flow velocity underground, the location of a second borehole will be determined in order to bring the warm water back to the earth's surface for use.

The BedrettoLab comes close to these real conditions, as the geothermal laboratory is covered by about one kilometre of rock and the rock has a suitable fracture system. ‘We are exploiting existing fractures and the fluids circulating in them and enriching the existing fracture structures with more water,’ explains project manager Maren Brehme. Many important parameters are already known from the rock volume in the BedrettoLab. For example, it is to be expected that a certain amount of water will flow away and not follow the main flow direction exclusively. However, it is important for the feasibility of the project to find out whether at least a large part of the injected water volume can be extracted again.

In addition to the ongoing test in the BedrettoLab, the BEACH project team is already in talks with an industrial company in Schaffhausen that has expressed interest in working with the BEACH researchers to implement the concept tested in the BedrettoLab in a pilot plant.

To learn more about BEACH, you can watch the following TV report (in German): 10vor10 (SRF) from August 2, 2024

To investigate PRECODE’s research questions, the rock volume to be excavated was extensively instrumented beforehand using various monitoring techniques, including seismic, hydraulic, deformation, and geophysical methods. One important research question is the impact of excavation methods on the EDZ, including a comparison of two techniques. The objective is to observe the evolution of the EDZ over a period of three to five years.

The first ten meters of the new tunnel were excavated using controlled blasting, while the remaining eleven meters were excavated using a technique known as “Line Drilling and Rock Breaking,” internally referred to as “Soft Excavation.” This method involved drilling numerous small holes around the tunnel perimeter to serve as anchoring points for a rock splitter, which was then used to break up the interior material. The objective of the Soft Excavation was to minimize excavation-induced damage, allowing the project to assess damage development driven purely by stress redistribution, in contrast to construction-induced damage caused by drill and blast.

Initial results clearly demonstrate the development of the EDZ around the tunnel in response to excavation. Identifying the characteristics of this short-term EDZ—particularly its location and extent—paved the way for the PRECODE research team to focus on the area of interest for long-term monitoring, where they will study how the damage evolves over time due to changing environmental conditions.

After this test section, excavation continued for another approximately 80 meters using the faster drill-and-blast method. As of the end of April, excavation of the side tunnel has been completed. Final tasks are now underway, including paving the tunnel floor with concrete and installing a metal mesh on the ceiling to ensure a safe working environment. This month, the drilling of the first boreholes from the new side tunnel is planned to continue the research efforts.

The PRECODE project is led by a research team at RWTH Aachen. Project partners are ETH Zurich, York University (Canada), Dalhousie University (Canada), and BGE Technology GmbH (Germany).

The BedrettoLab, situated in a 5.2 km-long rock tunnel, offers a unique opportunity to study the geology of the Alps and visit a one-of-a-kind underground laboratory operated by ETH Zurich. In collaboration with the Museum Sasso San Gottardo, visitors will have the opportunity to explore the BedrettoLab on five occasions, guided by trained tour guides.
During the approximately two-hour walking tour, visitors will learn about the history of the Bedretto tunnel. They will also discover geological phenomena visible on the tunnel’s unlined walls, offering a tangible experience of the Alps' formation. Additionally, they will visit the geothermal testbed and gain insight into why ETH Zurich has chosen this unique location for geothermal and earthquake research.

Costs and ticket booking

The cost per person for a tour is CHF 25. Tickets for the following dates can be booked on the Museum Sasso San Gottardo website: www.sasso-sangottardo.ch/bedrettolab.

• Saturday, June 14
• Sunday, July 13
• Friday, August 8 (tours on this day in German only)
• Saturday, September 20
• Saturday, October 11

More information on guided tours: www.bedrettolab.ethz.ch/en/about/visit/

After extensive preparation—including drilling boreholes, installing sensors, and manufacturing a specially designed fault deformation probe—the experiment commenced in late November. Over three weeks, approximately 1’100 cubic metres of water were injected into the target fault zone via two boreholes, using a custom designed remote control system. This volume is roughly equivalent to 5’600 bathtubs of water. Importantly, all water used was sourced from wells in the tunnel, ensuring no drinking water was wasted.

The injection was expected to induce a response in the fault structure due to increased pressure in the surrounding rock. Initial analysis indicates minor fault movements, with detailed calculations underway to determine the extent of this displacement. Additionally, the experiment revealed greater complexity in the fault zone than previously assumed. During high-pressure injection, small seismic events occurred more than 50 meters away from the injection site, and suggest the presence of an extensive fracture network.

These findings confirm that the fault zone can be activated, and provide crucial information for the design of the next FEAR experiments, which will focus on the controlled activation of specific fault zone segments.