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News Archive 2019


[Available in DE/FR] Erdbebenland Schweiz: Informationsanlass für Behörden

[Available in DE/FR] Erdbebenland Schweiz: Informationsanlass für Behörden

Was ist bezüglich Erdbeben zu tun? Eine Frage, die sich in Gemeinden und Kantonen immer wieder stellt. Oft gibt es nur wenige Berührungspunkte mit dem Thema Erdbeben, zum Beispiel im Rahmen von Bauvorhaben, Bewilligungsverfahren oder wenn die Behörden definieren, wie sie mit solchen Ereignissen umgehen.

Der Informationsanlass richtet sich an Behördenvertreter, die sich nicht schwerpunktmässig mit Fragestellungen rund um Erdbeben befassen, aber mehr darüber erfahren möchten. Ziel ist es, eine breite Wissensgrundlage zu vermitteln, die bei Entscheidungen in Bezug auf das Erdbebenrisikomanagement hilft.

Der Anlass findet am 23. August 2019 an der ETH Zürich statt. Anmeldung bis 5. August unter folgendem Link:


Using seismometers to monitor rapid mass movements

Using seismometers to monitor rapid mass movements

Above the village of Susten in the Canton of Valais, a stream is carving its way through a fascinating geological formation called 'the Illgraben'. Rock masses, both large and small, are constantly coming loose and falling away from the steep slopes of the gorge. Several times a year, mostly after precipitation, this creates a mushy mixture of sliding rocks, mud and water. These mudslides also rip out large blocks of limestone and quartzite and move down the valley at high speed as far as the River Rotten. Usually, no damage is caused near the Illgraben. In other places, in extreme cases mudslides move millions of cubic metres of rock distances of several kilometres. If these mudslides hit transport routes or human settlements, as happened in 2017 with the debris flow at Pizzo Cengalo, for example, the effects can be devastating. Sophisticated measuring systems can help to gain a better understanding of, or even predict, such processes. Researchers from the Swiss Seismological Service (SED), ETH Zurich's Laboratory of Hydraulics, Hydrology and Glaciology (VAW) and the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) are investigating this at the Illgraben site.

Predicting large mass movements is no easy matter. Indications of a potentially threatening event are hard to measure, the underlying physical processes are poorly understood and the affected areas can often only be accessed with difficulty. In remote alpine valleys, it is already quite a challenge to ascertain whether an event has even taken place because the spatiotemporal coverage offered by existing monitoring methods (e.g. satellites or geodetic instruments) is insufficient. Local seismic measurement networks offer a hitherto little-used alternative. Mudslides, rockfalls or rock avalanches trigger ground motion. Depending on the size of events, seismic stations can detect the associated movements from several kilometres away and in rare cases even up to several thousand kilometres away. Locally condensing the seismic network and ensuring fast data transmission can improve the monitoring of vulnerable areas and possibly warn of dangerous mass movements. Since 2017, for research purposes the SED has been running such a network including additional measuring instruments in the Illgraben. The knowledge gained from this should help to monitor and predict mass movements better and more reliably in the future.

Further information: Prof. Dr. Fabian Walter at VAW at ETH Zurich.


[Available in DE/FR] Beben am Südufer des Genfersees

[Available in DE/FR] Beben am Südufer des Genfersees

Am Dienstag, dem 28. Mai 2019, hat sich um 10:48 Uhr (Lokalzeit) am Südufer des Genfersees, südwestlich von St. Gingolph, westlich von Novel, auf französischem Boden in einer Tiefe von ungefähr 2 km ein Erdbeben der Magnitude 4.2 ereignet.

Die Erschütterungen waren im ganzen Seebecken und im Chablais gut zu spüren. Da sich das Beben relativ nahe der Erdoberfläche ereignet hat, wurde es vor allem im Gebiet des Epizentrums relativ deutlich verspürt. Die Anzahl der Erdbebenmeldungen nahm entsprechend mit der Distanz ab. Leichte Schäden sind bei einem Beben dieser Stärke vereinzelt möglich.

In den vergangenen Jahren haben sich in diesem Gebiet wiederholt oberflächennahe Beben oder Erdbebenschwärme ereignet, von denen die stärksten leicht verspürt wurden. Am 22. Dezember 2016 haben sich zum Beispiel in der Nähe des Ortes Novel zwei Erdbeben der Magnituden 3.0 und 3.4 innerhalb von 26 Minuten ereignet, die ebenfalls im Gebiet des Genfersees und im Rhonetal verspürt wurden. Damals haben sich innerhalb von zwei Wochen 13 weitere Erdbeben mit Magnituden zwischen 1.0 und 2.9 ereignet.

Das heutige Beben war damit das stärkste bisher. Mit Nachbeben ist in den nächsten Tagen und Wochen zu rechnen. Gleich starke oder gar stärkere Beben sind unwahrscheinlich, können aber nicht ausgeschlossen werden.   

Der Erdbebendienst wird in der Region im Laufe des Tages noch zwei weitere Messstationen installieren um die Nachbeben genauer zu beobachten.


Earthquakes and geothermal energy: lessons from Pohang

Earthquakes and geothermal energy: lessons from Pohang

In November 2017, a magnitude 5.5 earthquake shook the South Korean city of Pohang, injuring over 100 people and causing $300 million worth of damage. Just a short time later, suspicion arose that the quake might have been triggered by a nearby geothermal project. This impression was backed up by two scientific studies, one of which was written by employees of the Swiss Seismological Service (SED) at ETH Zurich (see the news article dated 26/04/2018). As a result, the South Korean government set up an international expert commission, whose members include Professor Domenico Giardini from ETH Zurich. This commission's recently published final report confirms that the geothermal project was indeed the cause of that highly destructive earthquake.

The commission examined the tectonic stress conditions, local geology, induced seismicity, drill data and details of the hydraulic stimulations associated with the geothermal project in Pohang, which was intended to construct a heat exchanger 4-5 km down in the crystalline bedrock. A similar petrothermal geothermal energy project was also attempted in Basel in 2006. Projects like this entail pumping fluid into the ground under high pressure. As expected, this triggers numerous minor quakes. Unnoticed by the operators, these injections in Pohang repeatedly set off earthquakes in quite a large previously unknown fault zone. This weakened the apparently tectonically pre-stressed fault line, leading to the magnitude 5.5 earthquake. Now that the causal link has been proved, the expert commission is asking what lessons can be learnt from the occurrence.

Its verdict on the project is far from positive. Indeed, looking back it can pinpoint failings at all stages of the undertaking. Before work began, geological studies had shown that some fractures were critically pre-stressed. Bearing in mind the proximity to a medium-sized city with a major industrial port, this finding should have prompted an adjustment of the project's risk assessment. Then the first hydraulic stimulations began at borehole PX-2. The geological reports state that large quantities of the fluid pumped into PX-2 seeped away. This is unusual, constituting another alarm signal, an indication that the borehole ran through a sizeable interference zone. Locally, the spillage of the injected fluid increased the pressure on the fault zone and already triggered numerous small earthquakes early on. Yet this increased induced seismicity was only analysed after the magnitude 5.5 earthquake.

The commission also looks into the two-month period between the last hydraulic stimulations and the damaging quake. This time lag has repeatedly been interpreted as indicative of no connection between the geothermal project and the earthquake. However, the report invokes findings from other projects which prove that induced seismicity often does not stop when hydraulic stimulations come to an end. The commission recommends involving the respective authorities and all relevant experts in the run-up to future projects, to draw up a comprehensive risk analysis and then keep it constantly updated. Furthermore, a reliable real-time monitoring system has to be set up, the processes and injection strategy must be constantly reviewed and, if need be, corrected, and risk mitigation measures need to be formally noted down and communicated.

Shortly after the earthquake in Pohang, the canton of Jura called for a review of the risk analysis for the planned petrothermal geothermal energy project in Haut-Sorne. The operator, Geo-Energie Suisse, has written an appraisal, which the SED is currently examining on behalf of the canton, taking account of all the known findings from Pohang. The SED is also involved in research work at the Bedretto Underground Laboratory for Geoenergies. There, along with other national and international partners, ETH Zurich, is conducting research to ascertain whether geothermal energy can be exploited safely, efficiently and sustainably using any existing technologies or procedures.


Science article "Managing injection-induced seismic risk"

Report by the commission (in Korean and English – scroll down and click on link to PDF file)

Science article "The November 2017 Mw 5.5 Pohang earthquake: A possible case of induced seismicity in South Korea"


Seismic water feature

You don't need to go far to watch the ocean waves. The water feature of the fountain at the seaside resort of Enge in Zurich shows how the waves of the Atlantic, the Mediterranean or the Baltic Sea are behaving, in real time. At least, this is the signal most frequently transmitted to the fountain's control system by the Swiss Seismological Service's seismic station at ETH Zurich in Degenried, near the Dolder. Roughly once a week, the dynamics of the fountain change, whenever a major earthquake occurs somewhere in the world. With a bit of luck you might even see smaller-scale Swiss earthquakes.

Although Switzerland's seismic network, comprising over 150 stations, is designed to record earthquakes, it can actually do much more. In addition to capturing the movements of ocean waves, the highly sensitive measuring devices detect the sounds emanating from forests, the noise made by flowing traffic and explosions in quarries. The Swiss Seismological Service (SED) only systematically analyses recorded seismic data after earthquakes and explosions. The Aquaretum, the fountain in Lake Zurich, uses a small frequency range of the existing signal, which causes the harmonic motion of the fountain's jets of water.

In all, 12 water jets propel the water shoots up to heights of as much as 35 metres. They are arranged in four groups of three, representing the acceleration, speed and path of the transmitted signal respectively. These three parameters are also fundamental for analysing seismological data.

The Aquaretum was gifted to population and visitors of Zurich by the Zurich Insurance Group and made with the support of Fischer Architekten, the sound artist Andres Bosshard and the team from Metallatelier.


The underground rock laboratory where even the smallest quakes are of interest

The underground rock laboratory where even the smallest quakes are of interest

A unique research facility, the "Bedretto Underground Laboratory for Geoenergies", in the Bedretto valley in the Canton of Ticino is currently nearing completion. Together with national and international partners, ETH Zurich will investigate technologies and processes that should enable the safe, efficient, long-term use of geothermal energy. The Swiss Seismological Service at ETH Zurich is installing seven additional seismic stations in and around the rock laboratory. These instruments will be sensitive enough to record even the minutest tremors in the surrounding area.

The Bedretto Lab will be inaugurated on 18 May 2019. Take the opportunity to visit this unique rock laboratory and explore the history of the Alps deep inside a mountain. What's more, in front of the entrance tunnel leading to the lab you can learn more about the work that will be done there, test your knowledge by completing a rock quiz, see how core samples are produced and acquaint yourself with the various measuring systems used.

Register here for a free tour (in German or Italian).

Click here for some practical transport information.

Further information about the rock laboratory


First potential marsquakes detected

First potential marsquakes detected

On 19 December 2018, the NASA InSight mission placed a seismometer on the surface of Mars. It aims to record marsquakes in order to to gain a better understanding of the planet’s interior. Since the very first day, the data recorded is continuously scrutinized by the Marsquake Service led by ETH Zurich, operated by the Seismology and Geodynamics group and the Swiss Seismological Service. At first, the data mostly showed the frequency and intensity of dust devils, whirlwinds which are very common on Mars. This already proved that the seismometer was performing well. On 6 April 2019 (Sol 128, 15:32 local Mars time), researchers from ETH on duty for the Marsquake Service discovered a potential marsquake in the data. It is the first signal that appears to have come from inside Mars, even though its exact cause is still an on-going scientific investigation.

Three other signals of likely seismic origin occurred on 14 March, 10 April, and 11 April 2019. These signals are more ambiguous to the InSight team than the one on 6 April, but do not appear to be clearly associated with atmospheric disturbances or other known noise sources. They are smaller than the event on 6 April and were only detected by the more sensitive broadband sensors. The team will continue to study these events to try to determine their origin.

Based on these first records, marsquakes seem to be distinct to earthquakes. According to their size and long duration, they are more similar to quakes recorded on the Moon by the Apollo programme. Whereas on Earth plate tectonics is the dominant process that provokes quakes, on the Moon the cooling and contraction causes tremors. The relevant processes at Mars are not yet fully understood. In any case, stress is built up over time until it is strong enough to break the crust. Different materials can change the speed of seismic waves or reflect them, allowing scientists to use these waves to learn about the interior of a planet and model its formation. The events recorded until now are too small to provide useful data on the deep Martian interior. Nevertheless, they mark a milestone of the InSight mission, proving the efficiency of the data processing and analysis capabilities, both developed at ETH Zurich.


Can deep boreholes trigger earthquakes?

Can deep boreholes trigger earthquakes?

More than 100 deep boreholes have already been drilled to depths of 400 m or more in Switzerland. Among other things, they have served to explore the subsoil, whether for tunnelling, exploiting geothermal energy, as potential sites for final repositories, prospecting for raw materials or tapping into sources of groundwater and thermal water. Hundreds of thousands of such boreholes have been sunk all over the world. So far, to our knowledge, no damaging earthquakes have been triggered solely by drilling deep boreholes. Consequently, the simple answer to the question asked above is that instances of damage caused solely by sinking deep boreholes, without any further interventions in the subsoil, are extremely unlikely. However, micro-earthquakes with magnitudes of less than 1 have been documented in association with the drilling of deep boreholes. Thanks to a dense seismic network, such microquakes can be reliably recorded. It can then be better determined whether such seisms are related to the sinking of deep boreholes or triggered by natural causes.

Despite the very large number of deep boreholes drilled worldwide, data on earthquakes occurring in connection with them are rather sparse. One reason for this is that the probability of such quakes is very low. Another is that many deep boreholes have been drilled in uninhabited areas, so potentially noticeable quakes may not have been felt and reported by the public. In many places, such boreholes have not been - and are still not being - seismically monitored. Consequently, it is impossible to reliably record smaller induced earthquakes. In Switzerland, for example, a number of microquakes were recorded when the borehole for the Basel geothermal energy project was cemented. The strongest of these had a magnitude of 0.7, meaning that it released 500 times less energy than a magnitude 2.5 quake. Earthquakes above this magnitude can usually be felt.

The physical processes behind earthquakes triggered in certain circumstances by drilling boreholes are well understood. Deep boreholes sometimes alter local stresses and pore pressures in rock, and in some cases this can reactivate a nearby tectonically pre-stressed fracture, causing an earthquake. However, such stress changes usually only occur in the following two situations: firstly, when drilling into a stratum with high fluid pressures. In this case, under certain conditions, the rock fluid (liquid or gas) can find its way into the borehole, causing overpressure that can usually be reduced in a controlled manner. Alternatively, the borehole is sealed at the corresponding place deep underground. Secondly, when boring into a very liquid-permeable stratum or rock of very low strength. If this happens, some of the drilling fluid or cement may enter the surrounding rock. The drilling fluid is needed to bring the drilling dust to the surface and stabilise the borehole during the driving process. Once a section has been drilled, the borehole is lined with cemented pipe to keep it open in the long term. In most cases, though, stress changes only affect small rock volumes. So the probability of activating quite a large, pre-stressed fracture and thus triggering a fairly large, potentially noticeable earthquake is extremely low.

The Swiss Seismological Service (SED) at ETH Zurich does not normally recommend seismic monitoring in its Guide for Managing Induced Seismicity for deep boreholes (e.g. exploratory drilling). Nonetheless, to record evidence and clarify the distinction between natural and induced seismicity, it may make sense to install an additional monitoring station near a drill site. For this very purpose, to cite just one example, the SED is currently consolidating its network on behalf of Switzerland's National Cooperative for the Disposal of Radioactive Waste (Nagra) with a view to monitoring exploratory drilling in northeastern Switzerland.


Earthquakes in Switzerland in 2018

Last year, the Swiss Seismological Service (SED) at ETH Zurich recorded more than 900 earthquakes with magnitudes of between -0.2 and 4.1 in Switzerland and its neighbouring countries. 25 of these quakes had a magnitude of 2.5 or more. Earthquakes of this size can usually be felt by the local population. So 2018 goes down as an average earthquake year, albeit one from which we can learn a lot. Because even very small quakes provide valuable information about the subsurface and thus make it easier to estimate future seismic activity.

Thanks to Switzerland's dense and highly sensitive earthquake measuring system, even the smallest quakes almost anywhere in Switzerland can be recorded and analysed. Earthquakes indicate the locations of more (or less) active faults today or over the years and provide insights into fracture processes deep beneath our feet. The seismic waves caused by earthquakes also offer data on the subsurface through which they pass. For example, the speed at which they travel tells something about the physical properties of the rock at the locations in question. These findings contribute towards more accurate risk assessment. So even 'quieter' earthquake years yield valuable knowledge.

The two strongest earthquakes felt over the largest areas by the Swiss population occurred on 17 January and 1 February 2018 in Austria's Kloster Valley (Montafon) near the Swiss border. Both quakes reached a magnitude of 4.1. The most powerful earthquake in Switzerland itself, with a magnitude of 3.2, occurred on 23 August near the twin-peaked mountain Dents de Morcles in the Canton of Valais. The SED received around 400 reports from people who felt this quake, mainly in the Rhone Valley, whose soft subsurface particularly intensified the shaking. Other earthquakes, some of which were also clearly felt, occurred on 15 and 16 May near Châtel-St-Denis in the Canton of Fribourg (with magnitudes of 3.1 and 2.9), on 3 November near Martigny in the Canton of Valais (magnitude 2.9) and on 29 December near Fribourg (magnitude 2.9). Only the quakes in the Kloster Valley ended up causing minor damage, such as cracks in buildings' façades.

In addition, last year saw the occurrence of some remarkable earthquake swarms. A swarm entails numerous quakes occurring over a fairly long period, without there being any clear sequence of foreshocks, mainshock and aftershocks. The most notable swarm involved a series of earthquakes northeast of St. Léonard, near Sion in the Canton of Valais. This sequence was related to a fault that has repeatedly been associated with phases of heightened seismic activity since 2014. It is believed to be part of the Rhone-Simplon fault, which appears to be broken into separate segments in this area. Another earthquake sequence worth mentioning occurred in the border area between Italy, France and Switzerland, in the east of the Mont Blanc Massif. Last year, the SED pinpointed the locations of close to 100 earthquakes with magnitudes between 0 and 2.2 in that area.

In general, in 2018, as in previous years, most earthquake activity occurred in the Valais region, the Canton of Graubünden and the areas along the Alpine front. Despite this concentration of seismic activity, historically it has been shown that no parts of Switzerland are earthquake-free regions. Based on the long-term average, a serious earthquake with a magnitude of 6 or more occurs in the earthquake country Switzerland every 50 to 150 years.

Download press release (PDF)

Download map (PNG)


Experiment investigates how faulted rock retains CO2

Experiment investigates how faulted rock retains CO2

In order to achieve the ambitious UN climate targets, it is not enough to reduce greenhouse gas emissions. As a complementary option, one can capture CO2 directly from industrial production or from the atmosphere and store it permanently in the deep underground. For enabling so-called negative emissions, sequestrated CO2 needs to be safely retained for centuries. Once injected into a reservoir, CO2 may escape again in two ways: through existing boreholes or through existing faults in the rock above the reservoir meant to seal it. Faults in this caprock may not only influence the long-term containment of CO2. They are also the place, where earthquakes may occur.

Currently, the physical and chemical parameters governing leakage through faults, and the effects of rock deformation and chemical interactions leading to induced seismicity, are not fully understood. There is further limited knowledge on Swiss-specific conditions, making it difficult to judge to what extent underground CO2 storage could be an option in this country. This is why scientists from the Swiss Seismological Service at ETH Zurich and the SCCER-SoE are conducting an experiment, in collaboration with the Department of Mechanical and Process Engineering and the Institute of Geophysics at ETH Zurich as well as Swisstopo and EPFL. The experiment is taking place at the Mont Terri rock laboratory and part of the ELEGANCY project funded by the European Commission and the Swiss Federal Office of Energy.

Scientists will investigate how CO2 migrates withing a rock with faults, under what circumstances induced seismicity may occur, and how such a storage should be monitored best. Therefore, they will inject small amounts of CO2-enriched saltwater into a borehole that cuts through a small fault zone. To study how the fault zone reacts to the CO2 injected, they will observe the stability of the rock and analyse the coupling between fault slip, pore pressure, and fluid migration. Active and passive seismic sensors will monitor the variations of seismic velocities around the injection and register possible micro-earthquakes with magnitudes below zero.

In contrast to a full-scale CO2 storage project, this experiment only investigates the relevant processes with small amounts of CO2-enriched saltwater. Nonetheless, its findings will contribute to a better understanding of the relevant processes influencing the migration of CO2 in faults. Thereby, the experiment will also contribute to an enhanced site characterization. Worldwide, about twenty CO2 storage projects are already in operation, each sequestering up to three million tons of CO2 per year, and numerous plants are in the planning. In Switzerland, there is currently no CO2 storage project planned. 

Learn more about the ELEGANCY project: