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News Archive 2020

2020-05-28

[Available in DE / FR] Weiterhin aktive Erdbebensequenz im Glarnerland

Seit Dienstag, dem 26. Mai 2020, ist im Sernftal (westlich von Elm GL) eine Erdbebensequenz aktiv. Sie begann um 07:50 Uhr Ortszeit mit einem Beben der Magnitude 3.1 (siehe vorangegangener Beitrag). Seitdem und bis am Mittag des 28. Mai 2020 konnten mit dem Messnetz des Schweizerischen Erdbebendienstes an der ETH Zürich (SED) 13 weitere Beben mit hoher Qualität lokalisiert werden. Die beiden stärksten Beben hatten Magnituden von 2.9 und 2.8 und wurden jeweils am Mittwoch, um 02:55 Uhr und 09:11 Uhr, nahe beim Epizentrum schwach verspürt.

Die Grafik oben zeigt, wie sich die Bebenaktivität über die Zeit entwickelt hat. Die Abbildung umfasst einerseits die 22 lokalisierten Beben (rot umrandet; darunter neun Beben geringerer Lokalisierungsqualität, die nicht im Erdbebenkatalog erscheinen). Anderseits sind weitere, sehr kleine Ereignisse abgebildet. Diese konnten nachträglich durch einen systematischen Vergleich der Wellenformen ermittelt werden; jene der kleinen Beben weisen ähnliche Muster auf wie die der standardmässig aufgezeichneten. Die dazu angewendete Methode des «template-matching» wird derzeit am SED erforscht und weiterentwickelt. Sie ermöglicht, solche Sequenzen noch besser zu verstehen.

In vorherigen Beitrag wurde bereits auf die Nähe zum Urnerboden Erdbebenschwarm von 2017 hingewiesen. In etwas kleinerer Entfernung ereignete sich 10 km westlich der aktuellen Beben am 17. März 2001 ein Beben der Magnitude 3.8 bei Linthal (GL). Im Gebiet der aktuellen Sequenz registrierte der SED bereits im Sommer 1987 eine ähnliche Erdbebenserie von damals 34 Erdbeben, die über einen Monat dauerte. Das stärkste Beben hatte eine Magnitude von 2.4. Eine Relativlokalisierung der Erdbeben zueinander zeigte, dass sie alle entlang einer fast senkrechten Störung auftraten, die Ost-West orientiert ist. Die Bewegung ist dabei dextral: Das heisst, dass egal auf welcher Seite der Verwerfung man sich befindet, die gegenüberliegende Seite sich nach rechts bewegt.

Erste vorläufige Untersuchungen der bisher aufgezeichneten Beben scheinen die fast gleiche Verwerfungsgeometrie für die jetzige Sequenz zu zeigen, was darauf hindeutet, dass das selbe Verwerfungssystem wie 1987 reaktiviert wurde. Solche, ungefähr Ost-West streichende (wie auch Nord-Süd streichende) Verwerfungen sind aus der Oberflächengeologie in diesem Teil der Alpen bekannt. Wie schon in der Sequenz von 1987 deuten vorläufige Analysen darauf hin, dass die aktuellen Beben relativ oberflächennah auftreten. Mit einer Tiefe von ca. 2 km liegen sie wahrscheinlich im Kontaktbereich zwischen Sedimentüberdeckung und kristallinem Grundgebirge. Aufgrund bestehender Unsicherheiten in der Tiefenbestimmung ist eine genauere Einschränkung derzeit noch nicht möglich.

Obwohl sich die seismische Aktivität in den letzten 24 Stunden verringert hat, ist es schwierig, eine Prognose über die Erdbebenaktivität in den nächsten Tagen und Wochen zu machen. Solche Schwärme können erfahrungsgemäss sehr unterschiedlich verlaufen. Es ist aber immer noch möglich – wenn auch wenig wahrscheinlich – dass weitere, noch stärkere Beben auftreten werden. Allgemein kann daran erinnert werden, dass grössere Erdbeben mit einer Magnitude von 6 oder mehr zwar selten sind, in der Schweiz aber überall und jederzeit auftreten können. Im Durchschnitt ist in der Schweiz alle 50 bis 150 Jahre mit einem Erdbeben mit einer Magnitude von etwa 6 zu rechnen.

2020-05-19

[Available in DE / FR] Erdbeben bei Sion

[Available in DE / FR] Erdbeben bei Sion

Am Dienstag, den 19. Mai 2020, ereignete sich um 08:10 Uhr Ortszeit ein Erdbeben der Magnitude 2.1 im Rhonetal, östlich von Sion (VS). Die Tiefe des Bebens lag in ungefähr 6 km. Trotz seiner relativ geringen Magnitude wurde das flache Erdbeben von zahlreichen Personen verspürt: Innerhalb von rund zwei Stunden nach dem Beben gingen beim Schweizerischen Erdbebendiest rund 80 Verspürtmeldungen ein, die meisten davon in Sion selbst und alle in einem Umkreis von nur 10 km. Das Rhonetal ist eine Region mit einer der grössten Erdbebengefährdungen in der Schweiz.

2020-04-07

[Available in DE / FR] Geothermieprojekt Haute-Sorne – Kanton erwägt Genehmigung zurückzuziehen

[Available in DE / FR] Geothermieprojekt Haute-Sorne – Kanton erwägt Genehmigung zurückzuziehen

In der jurassischen Gemeinde Haute-Sorne war vorgesehen, ein petrothermales Tiefengeothermieprojekt zur Stromerzeugung zu errichten. Die Frage nach dem mit dem Projekt verbundenen seismischen Risiko wurde vom Kanton erneut aufgeworfen, nachdem sich im November 2017 nahe der südkoreanisches Stadt Pohang ein Erdbeben mit einer Magnitude von 5.5 ereignet hat (siehe Aktuellbeitrag vom 24.05.2019 für eine Übersicht). Auslöser des Bebens war ein petrothermales Tiefengeothermieprojekt in unmittelbarer Nähe. Die Geo-Energie Suisse AG (GES), welche das Projekt in Haute-Sorne plant und betreiben möchte, wurde daraufhin von Kanton Jura aufgefordert, ihre Risikobeurteilung im Lichte der Erkenntnisse aus Südkorea neu zu bewerten. Anschliessend erhielt der Schweizerische Erdbebendienst (SED) an der ETH Zürich vom Kanton das Mandat, die aktualisierte Risikobeurteilung der GES zu prüfen.

Am 6. April 2020 hat der Kanton Jura den Bericht des SED veröffentlicht und seinen Entscheid für das weitere Vorgehen bekannt gegeben: Er erwägt, die Genehmigung für das Tiefengeothermieprojekt in Haute-Sorne zurückzuziehen. Alle Informationen sind auf folgender Seite publiziert: https://www.jura.ch/CHA/SIC/Centre-medias/Communiques-2020/Le-Gouvernement-envisage-de-revoquer-l-arrete-d-approbation-du-plan-special-cantonal-Projet-pilote-de-geothermie-profonde-a-Ha.html#

2020-02-24

The seismicity of Mars

The seismicity of Mars

Fifteen months after the successful landing of the NASA InSight mission on Mars, first scientific analyses of ETH Zurich researchers and their partners reveal that the planet is seismically active. The recorded data enables a better understanding of the interior of Mars, the primary goal of the InSight mission.

On 26 November 2018, the NASA InSight lander successfully set down on Mars in the Elysium Planitia region. Seventy Martian days later, the mission’s seismometer SEIS began recording the planet’s vibrations. A team of researchers and engineers at ETH Zurich, led by ETH Professor Domenico Giardini, had delivered the SEIS control electronics and is responsible for the Marsquake Service. With the first data coming in, the Marsquake Service, operated by researchers of the Swiss Seismological Service in collaboration with the seismology and geodynamics group at ETH Zurich and international colleagues, commenced full operation. On a daily basis, incoming data is analyzed and interpreted. However, only a fraction of the data is automatically sent to Earth due to transmission limitations. As soon as the marsquake service team spots distinctive features, they request the full-rate data for this period and scrutinize it upon arrival. Now, the journal Nature Geoscience published a series of articles on the results of the mission in the first months of operation on Mars.

As reported in these articles, InSight recorded 174 events until the end of September 2019. Since then, the measurements have continued leading to more than 450 observed marsquakes as of today, which have not yet been analysed in detail. This accounts for one event a day on average. The data allows researchers observing how seismic waves travel through the planet and unveiling its internal characteristics – similar to how x-rays are used in medical tomography. Before InSight landed, researchers had developed a wide range of possible models to represent the internal structure of the red planet. The recorded marsquakes, already after few months, enable refining the understanding of the structure of the planet and to reduce the uncertainties.

Marsquakes are similar to the seismic events we see on Earth, although they are generally of smaller magnitude. The 174 registered marsquakes can be categorized into two families: One includes 24 low-frequency events with magnitudes between 3 and 4, as documented in the papers, with waves propagating through the Martian mantle. A second family of marsquakes comprises 150 events with smaller magnitudes, shallower hypocentral depth and high frequency waves trapped in the Martian crust. “Marsquakes have characteristics already observed on the Moon during the Apollo era, with a long signal duration (10 to 20 minutes) due to the scattering properties of the Martian crust”, explains ETH Professor Giardini. In general, however, he says, interpreting marsquake data is very challenging and in most cases, it is only possible to identify the distance but not the direction from which the waves are arriving.

InSight opens a new era for planetary seismology. The SEIS performance exceeded so far expectations, considering the harsh conditions on Mars, characterized by temperatures ranging from minus 80 to 0 degrees Celsius every day and by strong wind oscillations. Indeed wind shakes the InSight lander and its instrumentation during the day leading to a high level of ambient noise. However, at sunset, the winds calm down allowing recording the quietest seismic data ever collected in the solar system. As a result, most seismic events detected on Mars by SEIS occurred in the quiet night hours. The challenging environment also requires to carefully distinguishing between seismic events and signals originating from movements of the lander, other instruments or atmospheric-induced perturbances.

The hammering by the HP3 instrument (another InSight experiment) and the close passage of whirlwinds (dust devils), recorded by SEIS, allow to map the physical properties of the shallow soil layers just below the station. We now know that SEIS landed on a thin, sandy layer reaching a few meters deep, in the middle of a 20 meter-wide ancient impact crater. At greater depths, the Martian crust has properties comparable to Earth’s crystalline massifs but appears to be more fractured. The propagation of the seismic waves suggest that the upper mantle has a stronger attenuation compared to the lower mantle.

InSight landed in a rather quiet region of Mars, as no events near the station have been recorded up to now. The three biggest events were located in the Cerberus Fossae region about 1’500 km away. It is a tectonic graben system, caused by the weight of the Elysium Mons, the biggest volcano in the Elysium Planitia area. This provides strong evidence that seismic activity on Mars is not only a consequence of the cooling and therewith the shrinking of the planet but also induced by tectonic stress. The total seismic energy released on Mars lies between the one of Earth and of the Moon.

SEIS, complementary to other InSight measurements, also meaningfully contributed data to better understand the meteorological processes on Mars. The instrument’s sensitivity to both wind and atmospheric pressure allowed identifying meteorological phenomena characteristic of Mars, including the many dust devils that pass by the spacecraft every afternoon.

More detailed results of the seismic analysis and additional findings of the InSight mission can be accessed in the series of papers recently published in Nature Geosciences: The seismicity of Mars, Crustal and time-varying magnetic fields at the InSight landing site on Mars, The atmosphere of Mars as observed by InSight, Initial results from the InSight mission on Mars

Learn more about the NASA InSight mission: https://mars.nasa.gov/insight/ and about ETH Zurich’s involvement in InSight: www.insight.ethz.ch

2020-05-26

[Available in DE / FR] Beben in den Glarner Alpen

[Available in DE / FR] Beben in den Glarner Alpen

Am Dienstag, dem 26. Mai 2020, hat sich um 07:50 Uhr Ortszeit etwa 3 km westlich von Elm (GL), im Sernftal, in einer Tiefe von ungefähr 4 km ein Erdbeben der Magnitude 3.1 ereignet. Bei einem Erdbeben dieser Stärke sind in der Regel keine Schäden zu erwarten.

Die Erschütterungen wurden in der Nähe des Epizentrums teilweise deutlich wahrgenommen. Am Schweizerischen Erdbebendienst der ETH Zürich gingen aber fast keine Verspürtmeldungen aus Entfernungen über 20 km ein.

In den vergangenen Jahren haben sich in diesem Gebiet vereinzelt spürbare Beben ereignet. Am 6. März 2017 erschütterte ein Beben der Magnitude 4.6 die ganze Innerschweiz. Sein Epizentrum lag aber 15 km weiter westlich, bei Urnerboden. Ebenso wie das heutige Beben ereignete sich auch das Urnerboden Beben in etwa 4 km Tiefe. Erdbeben in diesem Teil der Alpen liegen meistens weniger als 5 km tief, und damit relativ nah an der Oberfläche.

2020-04-29

Measures to combat COVID-19 also reducing seismic noise in Switzerland

Seismic measuring stations do not only record seismic waves. They also pick up tremors caused by other factors: these are known as seismic background noise. Humans are partly responsible for these constant movements of the Earth. For instance, road traffic or industrial activities may cause vibrations in the Earth’s crust. Their impact is typically greater during the day and lower at night and at the weekend. Wind, waves and the weather also cause the Earth to vibrate constantly. International studies have shown that levels of human-induced seismic background noise have decreased in many locations since the outbreak of the coronavirus pandemic. Measuring stations are thus indirectly detecting the effects of the lockdown and the associated drop in human activity. The Swiss Seismological Service at ETH Zurich has observed this phenomenon in Switzerland too.

Some of the stations belonging to the Swiss Strong Motion Network (SSMNet) in particular, many of which are located in urban areas, have recorded significant drops in seismic background noise. This has been the case for the stations in Martigny, Zurich, Basel and Geneva, among others. Since the state of emergency was declared, levels of background noise in these towns and cities have been almost as low on working days as they were at weekends before the lockdown began. Saturday and Sunday evenings have also been far quieter than usual since the start of the lockdown. The seismic noise levels recorded on weekend evenings have fallen to the level typically observed on a normal weekday evening in the relevant towns and cities – as a rule, more seismic noise is generated on weekend evenings than on weekday evenings.

Conversely, rural or alpine stations belonging to the national broadband network (SDSNet) have only recorded slight decreases in background noise because these areas are considerably less affected by vibrations from road traffic, trains and other human activities. Strong winds and other weather factors may nevertheless lead to increased levels of background noise in some areas, as may have been the case in northeastern Switzerland during the period under study (23 to 29 March 2020).

Due to the exceptional situation in Switzerland, measuring stations are now able to detect somewhat smaller earthquakes whose signals would otherwise be lost amid the background noise. The COVID-19 lockdown has therefore increased the sensitivity of earthquake monitoring in some parts of Switzerland, although the overall effect, at just 0.1 to 0.2 magnitude units, is not very great. By way of comparison, the sensitivity of monitoring is on average 0.5 magnitude units greater during the night than during daytime working hours. Latest data show at some stations that the seismic background noise has slightly increased over the last days. However, statements about compliance with lockdown measures cannot be derived from these data.

2020-03-18

[Available in DE] Erdbeben bei Vevey

[Available in DE] Erdbeben bei Vevey

Am Mittwoch, den 18. März 2020, ereignete sich um 02:54 Uhr Ortszeit ein Erdbeben der Magnitude 2.6 rund 10 km östlich von Vevey (VD). Die Tiefe des Bebens lag in ungefähr 9 km.

Das Epizentrum lag in der Gemeinde Montbovon (FR). Zahlreiche Personen in der Region haben das Beben verspürt.

Innerhalb des letzten Jahres gab es in der östlichen Genferseeregion mehrere, meist schwächere Erdbeben. Das stärkste Erdbeben des vergangenen Jahres in dieser Region ereignete sich am 28.05.2019 rund 13 km südwestlich von Vevey mit einer Magnitude von 4.2.

2020-02-17

LabQuake: taking lab scale studies of earthquakes to the next level

LabQuake: taking lab scale studies of earthquakes to the next level

In the beginning of February, the Swiss Seismological Service (SED) at ETH Zurich received a very special delivery: An 11-ton and 2.4 x 2.5 x 1 meters machine that can induce small earthquakes in palm-sized rock samples under conditions that are representative for the Earth’s crust in 4–8 km depth. This apparatus is called LabQuake and has been installed in the Rock Physics and Mechanics Laboratory under the responsibility of Dr. Claudio Madonna. LabQuake will enable a new research direction for the SED – Laboratory Seismology – aimed at gaining a better understanding of earthquake physics, for example in the context of induced earthquakes triggered by deep geothermal stimulations. Dr. Paul Selvadurai is leading the newly created Laboratory Seismology research group.

To develop a better understanding of nature, scientist often examine complex problems in the laboratory where they control the environment, repeat experiments and place dense arrays of sensors. With LabQuake, scientists induce tens of thousands of very small earthquakes – so-called nano-seismic events that produce the same order of energy as an insect flapping its wings once – in rock samples and observe how they form, what controls them, and why they cease. To this end, LabQuake is equipped with various sensors, measuring in great detail the evolution of nano-seismicity, strain and pore-pressure within the rock sample.

Unique in the world

LabQuake exposes rock samples of a maximum size of 7.6 cm to conditions at which deep geothermal energy plants operate: temperatures of up to 170° Celsius and a confining pressure of 170 MPa, which corresponds approximately to 1678 atmospheres or a 17.3 km high water column. The maximum force that the scientists can apply to the rock samples equals to the weight of 125 mid-size SUVs (about 2500 kN).

One of the first applications of LabQuake will be to repeat experiments on rock samples collected in underground research labs. LabQuake ideally supplements experiments at the deca-meter scale performed in the Grimsel In-situ Stimulation and Circulation (ISC) project. Scientists test hypotheses from this project and downscale them to LabQuake. Afterwards, they upscale the new findings and apply them to field scale experiments that are conducted within the Bedretto Laboratory for Geoenergies. Hence, LabQuake bridges the gap between projects at different scales and contributes to improve their accuracy and their performance.

The finances for LabQuake amount to roughly 1.2 million Swiss Francs and were secured through the start-up fund of the Professorship Wiemer, with contributions from the SNF R-equipment programme, the ETH equipment programme and the department of Earth Sciences.

To see how LabQuake was delivered to the SED, watch the time-lapse video here.

2020-01-25

[Available in DE / FR] Erdbeben im Turtmanntal (VS)

[Available in DE / FR] Erdbeben im Turtmanntal (VS)

Am Samstag, den 25. Januar 2020, ereignete sich um 20:13 Uhr (Ortszeit) ein Erdbeben der Magnitude 3.0 in einer Tiefe von ca. 4 km unterhalb des Turmanntals (VS) zwischen dem Val d’Anniviers und dem Mattertal.

Das Erdbeben wurde weiträumig verspürt, insbesondere im Rhonetal und Mattertal. Beim SED gingen in der Stunde nach dem Beben über 100 Verspürtmeldungen ein. Bei einem Erdbeben dieser Stärke sind keine Schäden zu erwarten.

Kurz zuvor, um 20:07 (Ortszeit), ereignete sich westlich von Realp (UR) ein Beben mit einer Magnitude von 2.4 bei einer Tiefe von rund 9 km, welches jedoch kaum verspürt wurde. Zwischen diesen beiden Beben gibt es keinen direkten Zusammenhang.

2020-01-14

Earthquakes in Switzerland in 2019

Last year, twice as many earthquakes occurred in Switzerland and in neighbouring countries compared to the long-term average. For nearly 50 of the total of 1,670 recorded earthquakes, the Swiss Seismological Service (SED) at ETH Zurich received five or more felt reports. Most of the quakes can be attributed to five active earthquake sequences that shaped seismic activity in 2019. One of them was in the canton of Valais, in the area between Anzère and the Sanetsch Pass. The other four occurred just over the Swiss border, at Courmayeur (Italy), Novel (France), Konstanz (Germany) and Chamonix (France).

In Switzerland, earthquakes often occur in sequences referred to as 'earthquake swarms', i.e. clusters of tremors occurring over time at one, specific location. An unusual feature of last year's seismic activity was the number of highly active earthquake sequences leading to a never previously recorded amount of events since modern seismic monitoring began in the 1970s. This also resulted in more felt earthquakes than usual. As a rule, quakes felt by humans have usually a magnitude of 2.5 or more. The last time a similar cluster of felt quakes occurred was back in 1964, when Sarnen, in the canton of Obwalden, experienced a distinct sequence of earthquakes over a period of several months, with magnitudes of up to 5.3. Although such a high level of earthquake activity as that experienced in 2019 is rare, it is neither unexpected, nor a sign of an increased seismic hazard over the months and years to come.

An earthquake swarm comprising 16 quakes in the canton of Valais prompted some 2,000 reports by members of the public who had felt them, the highest level of public attention gained all year. During the first half of November, more than 300 quakes occurred north of Sion, between Anzère and the Sanetsch Pass. The two largest events had a magnitude of 3.3. Initial analyses suggest that during this sequence several simultaneously activated faults influenced each other. By contrast, the seismic activity on the Bodanrück peninsula near Konstanz (Germany) appears to have been associated with a single activated structure in the geological underground. All the quakes there share a similar rupture mechanism. This swarm, comprising a total of seven felt earthquakes, indicates a seismically active fault structure in the Hegau-Bodensee region.

The largest earthquake in 2019, with a magnitude of 4.2, occurred at the end of May as part of the earthquake swarm near Novel (France). The SED received 600 felt reports for this event alone. The second strongest quake, with a magnitude of 3.7, occurred in connection with the swarm near Konstanz (Germany). The largest cluster of events in 2019 (410 quakes in all) was associated with the long-standing active sequence near Courmayeur (Italy) in the area of the Mont Blanc massif. 

The overall total of 1,670 recorded earthquakes is a new record. But this high number is not only due to the high level of earthquake activity in the past year, but can also be attributed to the steady densification and modernisation of the seismic network. For seismologists, it is helpful for more earthquakes to be recorded, because such measurements enable them to produce an ever more detailed picture of the Alps' geological underground and seismotectonics. Among other things, this can help to improve the basis for future seismic hazard and risk assessments.

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