Am Mittwoch, dem 16. Mai 2018, hat sich um 11:32 Uhr ein zweites Beben ereignet. Die Magnitude war mit 2.9 leicht schwächer. Das Epizentrum dieses Bebens liegt am selben Ort wie jenes des ersten (etwas 2 km südwestlich von Châtel-St-Denis). Das zweite Beben ereignete sich aber vermutlich noch ein bisschen näher an der Erdoberfläche.

The InSight Lander will place a seismometer, dubbed SEIS (standing for Seismic Experiment for Interior Structure), on the surface of Mars. As soon as data gathered by SEIS arrive at ETH Zurich, seismologists from the Swiss Seismological Service (SED) and the Seismology and Geodynamics Group (SEG) will analyse them as part of their routine work. However, with just one seismometer in place, this will be no easy task. Unlike on Earth, where seismologists can rely on very many recording stations to precisely determine the origin of a tremor, on Mars there will be no addtional reference points. For this reason, special care will be taken to extract as much information as possible from even the weakest signals indicating possible marsquakes, meteorite impacts or even minor tornadoes. For this purpose, staff at the Marsquake Service will combine methods taken from the early days of seismology, when there were only a few seismometers on Earth, with modern analytic methods for locating seismic events.

It is hoped that the results of the InSight mission will provide insights into one of the fundamental questions of planetary and solar system research, giving us a better understanding of the processes that created the Earth-like planets of the inner solar system (including Earth) more than 4 billion years ago. 

Learn more about the InSight mission and related acitivites at ETH www.insight.ethz.ch

See what our Mars scientists are telling about the @NASAInSight mission

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Seismograms of induced earthquakes are generally indistinguishable from those of natural earthquakes. Therefore, investigations focus on a range of indicators, taking into account the location of earthquakes, their depths, and the history of stimulation activities conducted underground. By analyzing publically available continuous waveform and geodetic data from satellites, the paper contributes to the understanding of the nature of the event.

The study shows that the mainshock and its largest aftershocks occurred within 2 km distance or less of the geothermal site. Furthermore, they are located within 1.5 km distance of an induced event, which occurred in April 2017 during one of the underground stimulation operations. These locations are confirmed by a Korean study, which has been simultaneously published in Science. In general, the closer an earthquake sequence is located to a geothermal site and to previous related seismic activity, as well as the sooner it happens after underground operations, the greater the chance of being related to it. The mainshock and the 46 aftershocks detected between 15 and 30 November 2017 all occurred at depths of 3 to 7 kilometres. Such depths are unusually shallow when compared to previously registered natural events in the area. The analysis of satellite data illustrates that the mainshock displaced the surface of the earth permanently by up to 4 cm, indicating that the activated, and previously unknown fault, is a steeply dipping and very shallow thrust fault that passes directly beneath the bottom hole section.

These indications combined lead to the conclusion that a connection between the magnitude 5.5 earthquake in South Korea and the nearby geothermal project is plausible. However, the mainshock occurred about two months after the last stimulation activities. So far, there is no quantitative model available that relates the injection activities conducted to the occurrence of this event. The Korean government has appointed an independent expert commission to examine all pieces of evidence and to evaluate if the event was triggered or induced by the nearby stimulation activities. To our understanding, the commission will (re-)analyze all available data and models, including microseismicity data, injection volumes, reservoir pressures, and detailed hydrological and geological data, which are essential to understand the relation between the injection operations and the earthquake sequence.

The Swiss Seismological Service (SED) at ETH Zurich has first informed the public (see SED news) in November 2017 about the Pohang earthquake in the context of the release of a good practice report on induced seismicity. At the same time, Geo-Energie Suisse AG had notified the canton of Jura, where currently the only EGS-style deep geothermal project in Switzerland has applied for a construction permit. In consequence, the canton instructed Geo-Energie Suisse AG to evaluate potential implications for the planned Haute-Sorne geothermal project. An immerged understanding of the link between the magnitude 5.5 Pohang earthquake and the nearby geothermal project is crucial for a safe and sustainable future exploitation of geothermal energy.

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Die Naturgefahrenfachstellen des Bundes:

• Bundesamt für Bevölkerungsschutz BABS
• Bundesamt für Umwelt BAFU
• MeteoSchweiz
• Schweizersicher Erdbebendienst an der ETH Zürich
• WSL-Institut für Schnee- und Lawinenforschung SLF