Geodigest

Abstract

The Matterhorn appears to be a massive, immovable mountain towering over the landscape near Zermatt, Switzerland, for millennia (Fig. 1). However, new research led by the WSL Institute for Snow and Avalanche Research SLF in Switzerland shows that this impression is wrong and that the Matterhorn is in fact constantly in motion, swaying gently back and forth approximately every 2 seconds (Andrei Ionescu, Earth.com, 23 December 2021). This subtle vibration with imperceptible amplitudes is caused by seismic energy in the Earth originated from oceans, earthquakes and human activity. Each object, including mountains, high-rise buildings, or bridges, vibrates at certain frequencies when affected by seismic energy. These natural frequencies depend on the geometry and material properties of the object. ‘We wanted to know whether such resonant vibrations can also be detected on a large mountain like the Matterhorn’, said the study lead author Samuel Weber, a researcher at the WSL Institute. Weber and his colleagues installed several seismometers on the Matterhorn, including one just below the summit, at 14 665 feet above sea level, and recorded all movements of the mountain at a high resolution in order to derive the frequency and direction of resonance. They found that the Matterhorn oscillates in a north–south direction at a frequency of 0.42 Hz, and in an east–west direction at a similar frequency. Compared to the reference station at the foot of the mountain, the measured movements on the summit were up to 14 times stronger. This phenomenon is due to the fact that the summit moves freely, while the base of the mountain is fixed, like a tree swaying in the wind. The researchers warn that such movements can intensify during earthquakes and potentially cause damage. ‘Areas of the mountain experiencing amplified ground motion are likely to be more prone to landslides, rockfall and rock damage when shaken by a strong earthquake’, said study co-author Jeffrey Moore, an assistant professor of Geology and Geophysics at the University of Utah. Such vibrations are not a peculiarity of this specific mountain. Other peaks, such as the Grosse Mythen, which is significantly smaller than the Matterhorn, vibrate in a similar manner. In fact, since it is smaller, the Grosse Mythen vibrates at a frequency four times higher than the Matterhorn. The Matterhorn is the largest mountain shown to vibrate. ‘It was exciting to see that our simulation approach also works for a large mountain like the Matterhorn and that the results were confirmed by measurement data’, concluded Moore.