An algorithm translates the various seismic signals to determine the shape and size of the water arcs. The jets are arranged in four groups of three and can propel the water to heights of over 2.5 metres. One jet in each group produces a spray of water representing either the acceleration, speed or path (displacement) of the recorded ground motion. These three parameters are also fundamental for analysing seismological data. 

A large version of this water feature can be admired at Zurich's Seebad Enge resort, where the Aquaretum fountain also displays real-time signals from the Zürichberg station. The fountain usually shows how the waves of the Atlantic, the Mediterranean or the Baltic Sea are behaving. The seismic station on the Zürichberg continuously records the vibrations of the ocean waves and instantly transmits these signals to the fountain's control system. Roughly once a week, the dynamics of the water feature briefly change whenever a major earthquake occurs somewhere in the world whose vibrations shake Zurich's geological underground. With a bit of luck, you might even see smaller-scale Swiss earthquakes on the fountain at Lake Zurich and its little sibling at the focusTerra exhibition.

focusTerra's special exhibition 'Waves - Dive in!' will run until 5 March 2023.

More information is available here.

Das letzte, ähnlich grosse Ereignis in der Nähe ereignete sich im März 1996 (ebenfalls Magnitude 4.1). Nach einer relativ ruhigen Phase ohne signifikante Erdbeben in den folgenden fast 25 Jahren gab es im September 2020 ein Beben mit einer Magnitude 3.5 und gestern Morgen eines mit einer Magnitude 3.0. Eine erste Analyse deutet darauf hin, dass das Beben Resultat einer in etwa Nord-Süd ausgerichteten schrägen Aufschiebung ist, wie auch schon das Magnitude 3.5 Beben in 2020.

Grundsätzlich sind Erdbeben in dieser Region nichts ungewöhnliches, der Kanton Wallis weist innerhalb der Schweiz die grösste Erdbebengefährdung auf. Es ist zu erwarten, dass in den nächsten Tagen und Wochen kleinere Nachbeben auftreten werden, die möglicherweise auch gespürt werden können. Die Wahrscheinlichkeit, dass in den nächsten Tagen oder Wochen noch ein ähnlich grosses oder grösseres Beben auftritt ist sehr gering, es ist allerdings auch nicht auszuschliessen.

The seismic nodes that were used are 5Hz geophones with integrated battery and digitiser (SOLOS provided by the University of Geneva) and 5Hz geophones with external digitiser and batteries (provided by the Geophysical Instrument Pool of the GFZ). Data from such dense seismic node deployments allow the researchers to gain a better understanding of the sub-surface. Thanks to the small size of the nodes, the research team finished the deployment within two weeks in June, despite the tough weather condition, steep terrain and long hikes to reach each dedicated site.

With the network, a special focus was given to the Northern region around Nesjavellir and the Southern Hverahlid, where the most productive boreholes of the geothermal field are located. A vehicle called vibrotruck (see fig. 2) passed through the Northern array and provided an additional source signal during the deployment time. Typically used in seismic exploration, the vibrotruck pressed a vibrating plate onto the earth’s surface. The low-frequency vibrations propagate underground and are reflected by the rock strata. These seismic waves were recorded by the installed geophones and gave further insights into the geological sub-surface.

After the deployment, the network was running successfully for two months and overlapped with another seismic network (COSEISMIQ), which is also operated by the SED. In August 2021, the research group travelled again to Iceland to dismantle both networks. The researchers expect that the high-density seismic imaging will allow them to illuminate the sub-surface in unprecedented detail.

Slow slips are most common in regions where tectonic plates slide over each other (in subduction zones), especially all around the edge of the Pacific Ocean, including Japan, New Zealand, North and Central America or near volcanoes such as Mt. Etna in Italy or Kilauea in Hawaii.

The team analysed the correlation between the characteristics of each slow event and the triggered seismic activity. The results show that shallower slow slips are more likely to generate larger seismicity compared to deeper slow slip processes. This information can now be used to improve a model to predict the changes and hazards associated with these specific types of events. The researchers hope that the database and modelling can be developed further to build a better understanding of those complex processes.

The research was recently published in the scientific journal “Science Advances” and is accessible under the following link: https://advances.sciencemag.org/lookup/doi/10.1126/sciadv.abg9718