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Earthquake Analysis

The Earthquake Analysis section covers the analysis and interpretation of recorded wave forms and seisms. Data recorded by the Swiss Seismological Service (SED) and its counterparts elsewhere form the basis for numerous research and service projects. For example, such data are essential for analysing the structure and composition of the Alps and their foothills, characterising fault properties, understanding the physics of earthquakes and seismological statistics, improving earthquake predictability or for distinguishing natural from induced earthquakes, including those caused by nuclear explosions.

The Earthquake Analysis section is divided into four research groups that focus on specific domains, but often also study shared topics of interest. The section is headed by Professor Stefan Wiemer.

The Induced Seismicity group is led by Professor Stefan Wiemer primarily researches the monitoring, understanding and assessment of hazards associated with man-made earthquakes. The topic of induced earthquakes is increasingly under discussion around the world, since many different kinds of human activity can trigger earthquakes underground. In Switzerland, induced earthquakes are mainly associated with geothermal power projects. In 2006, the high-pressure injection of water into the subsoil caused an earthquake in Basle with a magnitude of 3.4. In 2013, a magnitude 3.5 earthquake occurred near St. Gallen.

But earthquakes are also triggered when the subsoil is breached for other reasons, such as the injection of CO2 or wastewater, for the conventional and unconventional extraction of crude oil and natural gas through fracking, or in mining and tunneling. Furthermore, man-made alterations to the Earth’s surface can also trigger earthquakes, for instance when reservoirs are filled with water for the first time.

Assisted by local seismic networks, the Induced Seismicity group has monitored numerous earthquake sequences (e.g. St Gallen, Basle), sometimes working alongside the Swiss Federal Office of Energy (SFOE) and EnergieSchweiz (see GEOBEST-CH). Working in close collaboration with the Swiss Competence Centre for Energy Research-Supply of Electricity (SCCER-SoE), the group develops methods for estimating and minimising seismic hazards associated with geothermal power plants. In 2015, the group organised an international workshop on induced seismicity for more than 150 participants on Schatzalp mountain in Davos.

The Seismotectonics research group is led by Dr Tobias Diehl and analyses seismic data to gain a clearer understanding of the subsoil and the tectonic context. The main focus of the group's research is the Swiss Alps and their foothills, though its members are also involved in many international projects, for example – at the time of writing – in Bhutan and in the AlpArray project. For example, recordings of local, regional or teleseismic earthquakes can be used in a tomographic analysis to produce 3D representations of the velocity structure in the subsoil, whilst simultaneously pinpointing the location of such quakes with maximum accuracy. This also enables indirect conclusions to be reached about rock properties and physical parameters like density and temperature. Moreover, earthquakes' so-called dispersion characteristics can be used to make inferences about rupture processes or stresses in the subsoil.

The Statistical Seismology group is led by Professor Stefan Wiemer and investigates how statistical methods can serve to enhance our understanding of earthquakes and improve the forecasting of seismic events. The members of this group endeavour to devise and systematically test earthquake prediction models, which attempt to reproduce spatiotemporal seismicity patterns as accurately as possible and use them to forecast seismic activity over the coming days, months or decades. Statistical analyses of earthquake catalogues provide inferences about seismotectonics, such as the origin of magma underneath volcanoes, stress distribution in the Earth's crust, the aftershock sequence decay rate or the spread of liquids in the underground. Another key component of the group's work entails verifying the quality and homogeneity of earthquake catalogues and constantly improving them.

The Verification Seismology group is led by Dr Florian Haslinger. In 1996, the Conference on Disarmament (CD) in Geneva negotiated a Comprehensive Nuclear Test Ban Treaty (CTBT) prohibiting all atomic testing, so an International Monitoring System (IMS) was set up to verify the treaty's application. This IMS is a worldwide network of seismological, hydroacoustic, infrasound and radionuclide measuring stations equipped with the relevant communications technology and supported by the International Data Centre (IDC) and a Technical Secretariat. Switzerland is a key partner in the IMS and is represented in various working groups by the SED or Spiez Laboratory. The Davos seismic station (DAVOX) is also an integral part of the IMS.