Seismo Ge
Jen Ronnfeldt
Seismo-Live aims to collect all kinds of digital learning resources for seismology and offer them via this portal here. We currently have Jupyter notebooks but we plan to extend this with more detailed texts and videos.
The RS&BOOM combines all the features from the RS1D seismograph and the RBOOM infrasound monitor. It is a complete solution for monitoring the shakes of the Earth and the infrasonic booms in our atmosphere. Often the same source will produce both seismic signals, that resonate through the ground, and infrasonic waves, that travel through our atmosphere. With the RS&BOOM now you can record and explore the connection between these two data sets simultaneously.
This makes it possible to monitor seismic events and observe their vibrations move into the atmosphere (or vice versa), for example in the case of volcanic eruptions, avalanches, landslides and explosions. In addition, the infrasound sensor allows you to detect a huge number of other activities that a seismograph alone cannot measure. From incoming storms, planes flying overhead to auroras and bolides entering the atmosphere.
Seismic stations record any kind of ground motion, and therefore much more than just earthquakes. Our measurements are dominated by ambient seismic noise. These are vibrations caused by distant ocean waves, atmospheric pressure changes, or anthropogenic events such as blasts in quarries, traffic, construction work or explosions. This noise can be used to image the Earth beneath us, or to estimate the extent to which the local subsurface can amplify seismic waves.
Where relevant or necessary, this data can also be used to draw conclusions about events with a seismic footprint. US singer Taylor Swift's concert in Zurich on 9 June was one such event (others occurred on dates when she performed elsewhere). When a lot of people move rhythmically at the same time, this energy is transferred into the ground as harmonic vibrations and can be measured by nearby seismometers. The vibrations caused by the concert audience were visible at eight stations in the seismic network within a 6 kilometre radius of the Letzigrund Stadium. Beyond that, they got lost in other background noise. Previously, other large concerts or football matches have left similar marks on the seismic data.
How clearly human motion can be made out in the background noise depends on a number of factors. For example, there is the distance from the nearest seismic station. One person jumping immediately next to a seismometer will be enough to bring about visible fluctuations. As the distance from the seismometer increases, a larger number of people moving will be needed to produce this effect. For instance, if Switzerland had won the 2024 European Football Championship, families leaping up from their sofas would not have been reflected in the seismic data, whereas the enthusiasm of fans at large-scale public viewings might have been picked up. The subsurface is also a factor here. If crowds move about rhythmically on a soft subsoil, such as the gravel deposits of the Limmat Valley, the vibrations are stronger than on harder rock, although they are also attenuated more quickly with distance. The ground motion is further amplified when people cause a structure, such as a stand, to vibrate at its resonant frequency. Of course, the opposite effect can also be observed. For instance, the measures taken to combat the spread of COVID-19 led to a worldwide reduction in seismic noise caused by human activity from early to mid-2020 (SED news item).
As to whether Taylor Swift generates more or less enthusiasm than other acts or a football match also resulting in measurable seismic vibrations, this cannot be reliably determined from the seismic data.
From now on, the Swiss Seismological Service (SED) at ETH Zurich will publish a rapid impact assessment for any earthquake with a magnitude of 3 or more. This will inform emergency services, authorities and the public about the expected human and financial consequences of earthquakes that are felt over a wide area or cause damage, doing so shortly after these quakes occur. The assessments are based on the relevant quake parameters and the earthquake risk model of Switzerland published in 2023.
After a severe earthquake, emergency services must rapidly obtain a picture of the situation in order to deploy their resources as efficiently as possible. Rapid impact assessments contribute to this process, especially in the hours immediately after an earthquake when only limited or incomplete information is available from the affected area. It is also very important to keep the public informed in such a scenario. Although large-scale damage is only anticipated for earthquake magnitudes of around 5 or above, the SED already publishes a rapid impact assessment for smaller quakes with a magnitude of 3 or more. This helps to ensure that the whole process from creation through to application can be enacted and practised on a regular basis. On average, damaging earthquakes occur in Switzerland only every 8 to 15 years.
The rapid impact assessment values given are automatically generated estimates based on the earthquake risk model of Switzerland. However, the actual extent of the damage may differ considerably from these estimates, and the accuracy of any information is not guaranteed. There may be changes, for example, if the earthquake parameters underlying the impact assessment are updated during the detailed analysis. The decisive factor in the calculations is the modelled impact of the quake on potentially affected buildings. This makes it possible to estimate the approximate number of fatalities and people injured and seeking protection as well as the costs of damage to buildings. Different occupancy patterns depending on the time of day and seasonal occupancy fluctuations are currently not taken into account here, nor are human and financial losses resulting from damage to infrastructure (e.g. bridges, railway lines) or secondary damage (e.g. fire, landslides). In addition, rapid impact assessments of aftershocks disregard the damage that has already occurred and any increased vulnerability of buildings due to previous earthquakes.
As well as a publicly available overview of the expected consequences of the earthquake at national level, authorities and the Earthquake Damage Organization (EDO) will have access to cantonal overviews, showing the anticipated consequences of a quake for each canton and its communes. Access to the cantonal overviews is limited because the uncertainties at this level are even greater than at national level, meaning that the values need to be interpreted with due caution. The SED usually publishes the national overviews on its website (www.seismo.ethz.ch) within an hour of a quake, i.e. as soon as the data can be prepared.
Beim Schweizerischen Erdbebendienst an der ETH Zrich sind bereits in der Nacht ber 1'200 Versprtmeldungen eingegangen. Das Beben war im nrdlichen Aargau deutlich sprbar und stark genug, um einen Teil der Bevlkerung zu wecken (Intensitt IV). Die meisten Meldungen kamen aus Liestal, Schaffhausen, Mhlin, Pratteln und den umliegenden Gebieten. Vereinzelt wurde das Beben einem Umkreis von ber 100 km um das Epizentrum versprt. Innerhalb weniger Minuten wurden in der unmittelbaren Umgebung bereits 2 Nachbeben der Strke 1.7 und 1.4 gemessen. Bislang wurden keine Schden gemeldet.
Erdbeben sind in dieser Region nicht ungewhnlich. Das letzte sprbare Beben im Raum nrdlich von Laufenburg wurde am 12. Mrz 2018 mit einer Magnitude von 3.1 in 17 km Tiefe registriert, ebenso eines in Zell (20 km vom heutigen Beben entfernt) am 5. Mai 2009 mit einer Magnitude von 4.2 in 12 km Tiefe.
Es kann mit weiteren Nachbeben gerechnet werden. Solche Nachbeben treten blicherweise nach strkeren Beben auf, wobei die Hufigkeit und die Strke dieser Ereignisse mit der Zeit abnimmt. Weitere Beben mit einer hnlichen oder gar grsseren Magnitude wie das Beben um 3:06 Uhr sind zwar unwahrscheinlich, aber nicht auszuschliessen.
Ein Beben der Magnitude 4.4 ereignete sich am Dienstag, 4. Juni 2024, um 2:34 Uhr (Ortszeit) im Sihltal (SZ), rund 12 km sdstlich von Einsiedeln in einer sehr geringen Tiefe von ungefhr einem Kilometer. Weil sich das Beben so nahe der Erdoberflche ereignet hat, war es im Epizentralgebiet stark zu spren, jedoch gemessen an seiner Strke in einem vergleichsweise geringen Umkreis. Dies belegen die ungefhr 130 Versprtmeldungen, die in der ersten halben Stunde nach dem Beben beim Schweizerischen Erdbebendienst (SED) an der ETH Zrich eingegangen sind und praktisch alle von einer Epizentralentfernung von weniger als 30 km kamen. Auch typisch fr solch untiefe Beben ist, dass sie teilweise als Knall und weniger als Bodenerschtterung wahrgenommen werden. Bei einem Erdbeben dieser Strke knnen vereinzelt kleinere Gebudeschden (z.B. Risse im Verputz) bei den verletzlichsten Gebuden auftreten.
Es kann mit Nachbeben gerechnet werden. Solche Nachbeben treten blicherweise nach strkeren Beben auf, wobei die Hufigkeit und die Strke dieser Ereignisse mit der Zeit abnimmt. Weitere Beben mit einer hnlichen oder gar grsseren Magnitude wie das Beben um 2:34 sind zwar unwahrscheinlich, aber nicht auszuschliessen. Beben mit einer Magnitude von 4 oder mehr treten in der Schweiz im Schnitt alle ein bis zwei Jahre einmal auf. Das letzte Beben mit einer vergleichbaren Strke (Magnitude 4.4) in dieser Region ereignete sich am 25. Oktober 2020 bei Elm (GL). Das letzte versprte Beben im Kanton Schwyz ereignete sich am 4. Mrz 2015 stlich der Kantonshauptstadt. Es hatte eine Magnitude von 2.8.
Switzerland experiences between 1'000 and 1'500 earthquakes a year. Swiss citizens actually feel somewhere between 10 and 20 quakes a year, usually those with a magnitude of 2.5 or above. Based on the long-term average, 23 quakes with a magnitude of 2.5 or above occur every year. Find out more about the natural hazards with the greatest damage-causing potential in Switzerland.
c80f0f1006