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Every year, hundreds of earthquakes shake this German region, which was hit by a magnitude 6.1 earthquake in 1911.
Published on January 28, 2024 3:16 p.m
Reading time: 2 minutes
A graphic showing a severe earthquake that particularly struck West Germany in 2004. (MAXPPP)
It is a region of Germany where the earth shakes regularly. The southwest of the country, near the Rhine and Alsace, is even considered to be the area with the highest earthquake risk in Germany. The sector certainly lies in a plate collision zone, but part of the phenomenon remains unexplained.
At the Freiburg Seismology Center, tremors appear on the screens almost in real time in the form of color curves. In 2023, 466 earthquakes were recorded in the region. “We have earthquakes every day,” explains Stefan Stange, head of the seismology department. There we see the ones from last week, in red. There were six. It takes two or three seconds, nothing more. We don't know why they occur in these places and not 20 kilometers away. The building regulations are stricter here because it is assumed that there may be stronger earthquakes in the future.”
Stefan Stange, Head of the Freiburg Seismology Department (SEBASTIEN BAER / RADIO FRANCE)
A magnitude 5.4 earthquake in 2004
In order to better understand the phenomenon, 50 seismographs are measuring the tremors in the region. Technician Ralph Ortlieb maintains equipment in the basement of a building in Freiburg. “These devices are very sensitive,” says Ralph Ortlieb. “For example, a wood sawmill can interfere with measurements within a two-kilometer radius. They are installed in quiet places, underground, in cemeteries or near water tanks, these are the best places.”
Ralph Ortlieb, technician in the seismology department, in front of a measuring device in a cellar in Freiburg. (SEBASTIEN BAER / RADIO FRANCE)
99% of tremors are too weak to be felt by the population. The others, stronger, leave an impression. Dagmar remembers the Waldkirch earthquake in 2004, which had a magnitude of 5.4 at 2:52 a.m. “We were sleeping and suddenly we had the feeling that the house was vibrating,” says Dagmar. “It felt like stones were rolling towards us. That scared us.”
“We didn’t know whether to go out or stay inside. This has happened to us twice since we have been living here in Waldkirch.”
After each earthquake, residents' observations are collected at the Freiburg Seismology Center. Andrea Brüstle, who analyzes the data, explains a valuable resource: “It’s a short questionnaire on the Internet. You have to specify the time, place and intensity of the feeling. There is a scale: did I feel it a little, or more strongly, did the glasses collide? This allows us to evaluate.”
A magnitude 6.9 earthquake is expected to hit the region in October. But it will be an exercise organized by authorities to raise awareness among the population. Real earthquakes remain inherently unpredictable.