Scientists set off 8,000 earthquakes under the Alps - but everything was under control

These tremors were not felt on the surface. The goal was not to "create a dangerous earthquake", but to understand how underground seismic events occur and how to reduce risks when working in the subsurface.

Details

The experiment was carried out by specialists from ETH Zurich in the BedrettoLab. It is located in a tunnel more than 5 kilometres long under the Swiss Alps. Above the laboratory there are about one and a half kilometres of rock, so this place is suitable for studying processes that usually take place deep underground.

The project is called FEAR-2 - Fault Activation and Earthquake Rupture. Over the course of four days, the scientists pumped about 750 cubic metres of water into boreholes drilled into the tunnel walls.

Importantly, the researchers did not create a new fault. They worked with an existing fracture in the rock and tried to gently "push" it to move. The injected water reduces the friction inside the fault, which can cause the rock to shift slightly.

The instruments eventually recorded about 8,000 small seismic events. The scientists expected to come close to a magnitude 1 earthquake, but the actual tremors were weaker, ranging from about -5 to -0.14 in local magnitude.

For safety reasons, there were no people in the tunnel during the experiment. The entire process was controlled remotely from the ETH Zurich laboratory.

Why it's important

Experiments like this help us understand exactly how earthquakes start. Usually, seismologists set up sensors near known faults and wait for nature to tell them something. At BedrettoLab, the approach is different: the fault is saturated with sensors in advance, and then weak motion is induced under controlled conditions.

This is important not only for basic science. Human activity underground can also cause earthquakes. This happens with geothermal projects, resource extraction, fracking, or wastewater injection.

If scientists better understand what parameters trigger underground tremors, they can more accurately assess how not to trigger a dangerous event. As the researchers explain, the idea is to learn how to produce very weak earthquakes - and through that, understand how to avoid stronger ones.

Background

Induced earthquakes have already become a serious problem in various countries. In South Korea, for example, a magnitude 5.4 earthquake near Pohang in 2017 was linked to water injection at an experimental geothermal plant. In the US, similar risks are being discussed in connection with wastewater injection and oil and gas production.

Therefore, the researchers emphasise: the challenge is not to abandon all underground technologies. Geothermal energy, tunnels, storage and other projects can be important for the economy and energy. But we need to work with the subsoil in a safer way.

The experiment under the Alps is an attempt to understand the mechanics of faulting in a controlled environment where every weak tremor can be measured in near real time.

Source

AFP Deep beneath Swiss Alps, researchers trigger 8,000 tiny quakes in controlled test on Phys.org website tells about the FEAR-2 experiment at the underground BedrettoLab at ETH Zurich. Researchers pumped water into a natural fault beneath the Swiss Alps to trigger and study controlled microquakes.