One of the unsolved challenges for deep geothermal projects is how to mitigate unacceptably large, induced earthquakes. Unfortunately, the processes and conditions underpinning induced seismicity are still not sufficiently well understood to make useful predictions of the likely seismic response to geothermal reservoir development and exploitation. This predictability is further reduced by the sparse knowledge of the hydro-mechanical and geological conditions in the deep underground, and our lacking ability to map them well enough with current technologies. The seismic response to deep geothermal operations can, however, be monitored in real-time by seismological methods. These methods are, therefore, the core element of any traffic light system (TLS) for induced seismicity that was proposed in recent years.

In this project SIAMIS-GT (Improvement of SeIsmological Analysis Methods to better support cantonal authorities in questions related to Induced Seismicity in deep GeoThermal projects), we want to improve seismological analysis methods for monitoring induced seismicity by taking advantage of the waveform similarity observed in these earthquake sequences. The goal is to enable the SED to inform authorities, project developers and the population faster and more accurately about induced earthquakes that may occur during geotechnical projects (e.g., geothermal, mining, tunneling, etc.). We plan to apply similarity and repeating earthquake analysis to induced seismicity to improve the understanding of the source mechanics (i.e., distinction of natural versus induced seismicity, improved detection, localization and characterization). With these methods we also hope to be able to resolve aseismic changes in the subsurface that cannot be resolved using classical methods in real-time.

Figure on the left: Illustration of the basic principles of similarity location. Upper left: waveforms of 7 template earthquakes used for template matching of the Diemtigen swarm. Upper right: Epicenter map of 306 relocated earthquakes color-coded by highest similarity to the 7 templates. Red diamonds indicate the location of the templates. Notice that earthquakes cluster closely around the template they are associated to by waveform similarity. Bottom: Relationship between inter-event distance and waveform similarity for each template with respect to the 306 relocated earthquakes. Color indicates the reference template. It can be clearly seen that similarity decreases strongly with inter-event distance and that individual relationships can be derived for every reference template.

In the last few years, major and damaging earthquakes were felt in regions supposedly affected by a low rate of natural seismicity. Such events have become an extremely important topic of discussion in both Europe and North America, since several major events were associated to industrial activities. The main focus of this proposed research is the study of induced seismicity during exploitation of natural underground resources. More specifically, this proposal focuses on one side on a detailed understanding of the deep fault and/or fractures reactivation associated with the fluid injection. On the other side, the proposed research plans to investigate the mitigation of large magnitude induced seismicity, which may pose at risk the affected population and structures, as well as acting as obstacle to the development of new techniques for the exploitation of deep underground resources. First the project aims to understand the physics associated with the induced seismicity caused by anthropogenic activities. Secondly, the project aims to investigate in which conditions fluid-induced seismicity can be used as a tool. For example, the shearing process of fault and fracture, or the creation of new fractures, are needed to increase the permeability, and hence to enhance the fluid circulation at depth, eventually resulting in a more efficient energy production. However, such processes may, at the same time, produce seismicity that can be felt by local population.

• How is the induced seismicity affecting the growth of a geothermal reservoir? When does it act as a potential seal breaching during storage operation?
• Is it possible to use induced seismicity to develop a high permeability system, while constraining the earthquakes maximum magnitude? Or can a gas be stored in a safe (no seismic) way?

Understanding the fundamental processes will help in finding new methods to safely extract energy, whose request nowadays is constantly increasing.

The project will address the above open questions by theoretical studies, laboratory, and applied fieldwork. I plan to use data collected from on-going experiments (laboratory and in-situ) to improve numerical models. Numerical tools to be used include: thermo-hydromechanical modeling (THM), discrete fracture network (DFN), and statistical, as well as hybrid simulators.

Der SED konnte in den letzten Jahren mehreren schweizerischen Tiefengeothermie-Projekten bei der seismischen Überwachung zur Seite stehen und so einen konstruktiven Dialog mit Betreibern und kantonalen Behörden beginnen. Auf diesen Erfahrungen aufbauend, hat der SED erste Empfehlungen für kantonale Bewilligungs- und Vollzugsbehörden entwickelt, wie mit der Problematik der induzierten Seismizität in verschiedenen Phasen eines Tiefengeothermie-projektes umzugehen ist. Diese Empfehlungen beruhen jedoch bislang auf Erfahrungen aus nur wenigen gut dokumentierten Projekten. Die praktische Erfahrung mit ihrer Umsetzung fehlt in der Schweiz bisher weitgehend. Es ist deshalb schwer abschätzbar, wie gut diese Empfehlungen im lokalen Kontext (geologisch, politisch, kulturell) anwendbar sind und welche Anpassungen gegebenenfalls getroffen werden müssen. Eine weitere wichtige Fragestellung ist in diesem Zusammenhang, wie Richtlinien und Vorschriften aus anderen technischen oder behördlichen Bereichen mit seismologischen Empfehlungen zur Vermeidung von induzierter Seismizität wechselwirken und vereinbar sind. Mögliche Konflikte lassen sich häufig nur in der praktischen Umsetzung von Projekten und durch die enge Zusammenarbeit des Seismologen mit Genehmigungsbehörden und Betreibern aufdecken und lösen. Ebenso wichtig ist die regelmässige Überprüfung und Anpassung aller relevanten Richtlinien und Vorschriften auf der Grundlage des wachsenden Kenntnis- und Erfahrungsstandes. Wenn immer möglich sollte dies im Konsens mit allen Interessengruppen geschehen.

Im Projekt Geobest-CH wird der SED daher weiter grundlegende Datensätze zur Entstehung der induzierten Seismizität bei Tiefengeothermieprojekten in hoher Qualität und Auflösung sammeln, auswerten und interpretieren. Ausserdem kann der SED so die Kantons- und Bundesbehörden bei ihren Genehmigungs- und Überwachungspflichten in allen Phasen eines Tiefengeothermieprojektes seismologisch beraten und unterstützen. Der SED will so dazu beitragen gleiche Bewertungsmassstäbe bei der Umweltverträglichkeitsprüfung über kantonale Grenzen hinweg zu schaffen und kurz- bis mittelfristig die Vereinheitlichung, und damit eine erhebliche Erleichterung und Beschleunigung, dieses Verfahrens ermöglichen. Über eine zentrale Webseite soll die Öffentlichkeit unabhängig, aktuell und fachlich kompetent zum Thema induzierte Seismizität informiert werden, um eine sachliche Diskussion aller Interessengruppen zu unterstützen.

Im Rahmen des Forschungsprojektes GeoBest führt der Schweizerische Erdbebendienst (SED) seit Frühjahr 2012 die seismologische Überwachung des Geothermieprojektes der Stadt St. Gallen durch. Dazu hat der SED in Zusammenarbeit mit den Sankt Galler Stadtwerken sechs neue Erdbebenmessstellen im Raum St. Gallen errichtet. Ziel der Überwachung ist es, mögliche kleine Erdbeben - sogenannte Mikrobeben - in der Umgebung der Tiefbohrungen zu detektieren und abzuklären, ob diese in Zusammenhang mit dem Geothermieprojekt stehen oder natürlichen Ursprungs sind. Ausserdem werden durch das Projekt wichtige Grundlagendaten für ein besseres Verständnis der Tiefengeothermie gesammelt, die als unentbehrlicher Erfahrungsschatz die Planungssicherheit der kantonalen Behörden und Projektbetreiber bei zukünftigen Geothermieprojekten gewährleisten sollen.

Nach der Einstellung des Geothermieprojekts im Frühjahr 2014 führt der SED die Überwachung in reduzierter Form für mindestens zwei weitere Jahre fort.

The exploitation of underground energy resources as well as the use and expansion of hydropower are, like any other energy technology, not risk free. To address this risk, we develop upon the holistic concept of risk governance and community resilience, advocating a broad picture of risk: In addition to risk analysis and risk management, we also investigate how risk-related decision-making unfolds when a range of actors is involved. This requires coordination and possibly reconciliation between a profusion of roles, perspectives, goals and activities. Developments include: a rigorous common methodology and a consistent modelling approach to hazard, vulnerability, risk, resilience and societal acceptance assessment of energy technologies; a stress test framework and its application to assess the vulnerability and resilience of individual critical energy infrastructures, as well as the first level of interdependencies among these infrastructures; standardized protocols, operational guidelines and/or softwares for monitoring strategies, hazard and risk assessment during all project phases (including real-time procedures), and finally for mitigation and related communication strategies.

The exploitation of underground energy resources as well as the use and expansion of hydropower, are, like all energy technologies, not risk free. The risks identified in the domain of deep geothermal are induced seismicity and other risks (e.g. borehole blowout, environmental risks). The hazard factors for hydropower are those classically affecting large arch or gravity dams, aggravated by the pronounced topography of the Alpine region and by the rapidly changing climatic conditions in the Alps. How these risks potentially impact our society, is, of course dependent on the vulnerabilities of our buildings, our infrastructure and our communities. Moving towards a safe and more resilient energy sector requires tools for hazard and risk assessment, particularly in the low probability-high consequence event settings. Furthermore, the tools have to be closely integrated with related communication and public engagement strategies, as perceived risks actually do impact energy source design and mitigation strategies. A comprehensive risk governance framework is necessary, but not yet existing. This project aims to develop such a framework by integrating risk assessment and related risk perception models and tools. This should lead to a communication strategy for future projects. We develop a holistic concept of risk governance from a truly multi-disciplinary perspective, advocating a broad picture of risk: not only does it include risk assessment and assessment of ability to recover, but it also looks at how risk perception and risk-related communication can be organized. This work is divided into 6 PhDs (attached to SCCER-SoE T4.1): Induced seismic risk (led by SED); Renewable energy risk management & optimization; Accident risks at dams; Vulnerability of the Swiss built environment; Multi-risks and interdependencies; Assessing and monitoring risk perception.

This is the 3rd subproject of the „ENSI – SED-Erdbebenforschung zu Schweizer Kernanlagen“ project.

Subproject 3 aims at studying the relevancy of induced seismicity for the disposal of nuclear waste at geological depth. We will update/develop physics-based modeling of induced seismicity, and we will apply such models to the case of nuclear waste disposal. Moreover, the approach will be validated by reproducing the observations from the “Fault Slip experiment” at Mont Terri underground laboratory. Finally, numerical modeling will be performed to study the seismicity induced by tunnel excavation, as well as to better understand the possible occurrence of seismicity by temperature changes around disposal site. Collaboration with Subproject 1 and 2 will be crucial to properly estimate the hazard and risk of induced seismicity on geological nuclear waste disposal.

Scientists from the SED are exploring the potential of Earthquake Early Warning (EEW) in Central America. Funded by Swiss Agency for Development and Cooperation (SDC) at the Federal Department of Foreign Affairs (FDFA), scientists are the SED are working with colleagues at INETER, the agency responsible for monitoring seismicity in Nicaragua, to build and implement a prototype EEW system first in Nicaragua and hopefully extended to cover the wider region in Central America. The region suffers from large tsunamegenic earthquakes generated along the subduction zone (most recently M7.7 in 1992 and M7.3 in 2014), and also moderate crustal earthquakes that have in the recent past produced heavy damage, such as the M6.2 1972 earthquake that devastated Managua.

Earthquake Early Warning (EEW) is a tool that can rapidly characterize on-going earthquakes, and potentially provide seconds to 10s of seconds notification of impending strong shaking in advance of its occurrence. EEW can play an important role as part of a seismic risk reduction program, which is critical in the Central American region that has such a high seismic hazard. Additionally, making a seismic network capable of operating and maintaining an EEW system requires the network to achieve the highest standards in network performance - including station quality, speed and reliability of data communications, and robustness of the seismic network hub that runs the EEW software. Optimal network performance is also critical for other applications such as tsunami warning, volcano monitoring, and enables downstream scientific studies, eg on local Earth structure.

At the beginning of June, the SED visited INETER to evaluate the capability of the local seismic network and install first versions of the EEW software. Days after, on 9 June, a shallow M6.3 event occurred on the border with El Salvador that was detected by our system after 29s. Though optimisation is required to speed up the system, the infrastructure shows promise.

The project objectives are to 1) review the performance of, and propose improvements to the seismic network of Nicaragua, optimizing its capacity for EEW; and 2) to develop EEW algorithms tailored to the seismicity of Nicaragua and Central America, implement them in standard open source software available at INETER, and transfer operation to INETER.

A prototype EEW implementation will be developed that demonstrates the end-to-end functioning of the system and includes a limited number of recipients of EEW information. The project will propose the next steps towards a public EEW system for Nicaragua.

AlpArray is a European initiative to advance our understanding of orogenesis and its relationship to mantle dynamics, plate reorganizations, surface processes and seismic hazard in the Alps-Apennines-Carpathians-Dinarides orogenic system. The initiative integrates present-day Earth observables with high-resolution geophysical imaging of 3D structure and physical properties of the lithosphere and of the upper mantle, with focus on a high-end seismological array.

AlpArray is a major scientific collaboration with over 40 participant institutions. One of the main actions of the AlpArray initiative is to collect top-quality seismological data from a dense network of temporary broadband seismic stations. This complements the existing permanent broadband stations to ensure homogeneous coverage of the Alpine area, with station spacing on the order of 30km. 24 institutions are currently involved in the AlpArray Seismic Network (AASN), which will eventually install over 250 temporary stations in 12 countries. The AASN officially started on 1 January 2016 and will operate for at least 2 years. A complimentary ocean bottom seismometer (OBS) component is expected in 2017.

The Swiss contribution to the AASN is completed, with 23 temporary stations installed in Switzerland, Italy, Bosnia and Herzogovina, Croatia and Hungary. All national broadband stations also contribute to the AASN.

The Seismology and Geodynamics group (SEG) and the Swiss Seismological Service (SED) at the ETH in Zurich take leading roles in the project. Prof Edi Kissling is the project coordinator. Irene Molinari (SEG), John Clinton (SED) and Gyorgy Hetenyi (former SED, now at the University of Lausanne) lead AlpArray working groups, Irene Molinari also manages the Swiss component of the AASN.

More information is available on the project website.

Um in Zukunft die Gefahren von natürlichen und induzierten Erdbeben besser abschätzen zu können, braucht es ein genaueres Verständnis von Verwerfungszonen in tektonisch aktiven Gebieten wie der Schweiz. Mit Hilfe geophysikalischer Abbildungsverfahren und geologischen Kartierungen wurden in den letzten Jahren zahlreiche Verwerfungen in den schweizerischen Alpen und im nördlichen Alpenvorland identifiziert. Allerdings treten in vielen Fällen Erdbeben abseits dieser kartierten Verwerfungen auf, was die Frage nach den tektonischen Prozessen und Mechanismen aufwirft, die diesen Erdbeben zugrunde liegen.  

Ziel dieses Projektes ist es, durch verbesserte geophysikalische Inversionsverfahren die Strukturen von Verwerfungszonen hochauflösend abzubilden und daraus Erkenntnisse über mechanische Eigenschaften der Bruchsysteme abzuleiten. Dazu werden unter anderem Verfahren der seismischen Tomografie mit hochauflösender Erdbebenlokalisierung kombiniert. Die Anwendung konzentriert sich auf zwei Regionen in der Schweiz: (i) einer äußerst aktiven Erdbebenzone nördlich des Rhônetals im Kanton Wallis, (ii) einer Verwerfungszone nahe St. Gallen, die während Stimulationsmaßnahmen für ein geplantes Geothermiekraftwerk aktiviert wurde.

Durch die Anwendung verbesserter Abbildungsverfahren erwarten wir zum einen neue Erkenntnisse über den Zusammenhang zwischen existierenden Verwerfungen und dem Auftreten von Erdbeben. Zudem sind die beiden Untersuchungsgebiete von hoher gesellschaftlicher Relevanz. Das Wallis ist die Region mit der größten seismischen Gefährdung der Schweiz und ein Großteil der gegenwärtigen Seismizität in diesem Gebiet steht in Verbindung mit der Erdbebenzone nördlich des Rhônetals. Die St. Gallen Verwerfungszone bietet Gelegenheit zur Untersuchung der Erdbebengefährdung im dicht besiedelten Molasse Becken, welches potentieller Standort zukünftiger Geothermieprojekte und atomarer Endlager ist.

This project is carried out under a contract with the National Cooperative for the Disposal of Radioactive Waste (Nagra). It provides an independent monitoring of the earthquake activity in the area of the proposed nuclear waste repositories in northern Switzerland. Detailed microseismic analysis will help to identify active fault zones and provide insights into the underlying seismotectonic processes in the vicinity of proposed sites, which has direct implications on the seismic hazard assessment. The SED provides results of this project in a transparent manner and all data acquired are made available for public access (see SED declaration on transparency [link]).

Within this project, the Swiss Seismological Service (SED) constructed ten new seismic stations in northeastern Switzerland and southern Germany to improve monitoring capabilities for very small earthquakes. Monitoring of weak seismic events in this region is challenging, because the study region is densely populated and sediments of the Molasse basin dominate the surface geology. A novel step-wise optimization approach was developed to ensure an optimum configuration of the new stations. To reduce the seismic background noise, three of the ten new sites were equipped with borehole-sensors, located at depths of 120–150 m below the surface. The new stations are fully operational since December 2013 and will observe the local seismicity in northern Switzerland for a minimum of ten years.

The newly installed stations complement the five stations installed in 2003 under a first agreement with Nagra. With these ‘Nagra’ stations, together with stations of the Swiss National Seismic Network and stations of neighboring networks in Germany, the project aims to monitor earthquakes down to magnitudes of 1.0 and smaller in the study area. We intend to achieve an overall catalog completeness of Mc 1.3 throughout northeastern Switzerland and location errors less than 0.5 km in epicenter and less than 2 km in focal depth within the study region. Accurate earthquake locations are essential for seismotectonic interpretations. Within this project we therefore aim to improve location accuracy, especially for focal depths, of past and future earthquakes in the region.

Bhutan, a kingdom in the Eastern Himalayas, is living in self-imposed isolation: in order to preserve local culture, traditions and the environment, foreigners can enter in groups and in limited number only. Consequently, our geoscientific knowledge is very limited compared to other parts of the orogen. The first geological map was compiled in 1983 by the famous Swiss geologist Augusto Gansser. From a geophysical perspective, Bhutan is almost a blank spot: only very limited information exists on seismicity which shows a lower level of earthquake activity compared to other parts of the Himalayas; there is knowledge neither of the structure nor of the physical properties of the crust and the lithosphere. Illuminating the deep structure of Bhutan and comparing it with the much better known Central Himalayas of Nepal is highly relevant both for evaluating the earthquake hazard and for improving our geodynamic picture of the orogen.

We conducted a temporary seismic experiment in Bhutan. Two densely spaced profiles across the orogen allow us to produce the first images of the structure of the lithosphere in the Eastern Himalayas, as well as give an insight into lateral variations along the mountain belt. Our network provides reliable information on seismicity in Bhutan and establishes the first seismic velocity model of the crust. Furthermore, we will apply ambient noise tomography to map the physical properties of the lithosphere. The results will be interpreted jointly with gravity data to build physical models of the Eastern Himalayas as well as to draw conclusions on its geodynamics. Especially, seismotectonic studies that we plan to conduct by comparing different segments of the Himalayas may shed light on the origin of the apparent seismic gap in Bhutan.

Augusto Gansser, "Geology Father of the Himalayas" and first geological mapmaker of Bhutan, has passed away earlier this year (2012), at the age of 101. We would like to dedicate this experiment to his memory.

Outreach

• Article on the project results in Kuensel, Bhutan's most read newspaper: part I, part II (2015.05.09. and 16.)
• Interview in ETH Life [en] [de] (2013.02.12.)
• Article in the Newsletter of the Society Switzerland-Bhutan (2013.06.)

The Eastern, "straight" part of the Alps is home to a number of open questions. The most widespreadly known question is about lithospheric slab hanging beneath the Eastern Alps. Is it Adriatic (Lippitsch et al. 2003)? Is it European (Mitterbauer et al. 2011)? What is its extent and the related velocity anomaly?

Beyond carrying out tomographic calculations, one can also characterize the fabric of the lower crust with receiver functions. In the India-Asia collision zone this has helped to point out that the main lithosphere boundary is located at a very different place than the surface boundary of deformation. Anisotropic receiver function calculations are therefore one of the first tools to be applied on EASI data, with the main question of determining the role of the lower crust in shaping the orogen.

A recent Moho map compilation reveals another interesting features beneath the Eastern Alps and between the Europe and Adria plates: a Moho "gap" or "hole" (Spada et al. 2013). Near 47°N latitude and between 12° and 15.5°E longitude the crust-mantle boundary is not defined, or at least it does not appear as a sharp discontinuity. Mapping the extent of this hole, and characterizing the velocity gradient from crustal to mantle conditions is an interesting goal to tackle.

The relationship of the Alpine orogen to the adjacent foreland basin and the lithospheric blocks of the Bohemian Massif, with their own characteristic seismic signatures, is a structural target of EASI.

Our research methods include tomography, ambient noise analysis and receiver functions, with anisotropy included in all three types of investigations. The depth range of investigations encompasses the crust and the mantle lithosphere, down to the LAB.

InSight (Interior exploration using Seismic Investigations, Geodesy and Heat Transport) is a NASA Discovery Program mission that will deploy a single geophysical lander on Mars to study its deep interior. This is the first comprehensive surface-based geophysical investigation of Mars. The overarching mission goals are to illuminate the fundamentals of formation and evolution of terrestrial (Earth-like) planets by investigating the interior structure and processes of Mars, and more specifically to determine the thickness, structure and composition of the crust, mantle and core, and to measure the rate and distribution of seismic activity and the rate of meteorite impacts. The Mission should land in November 2018 and have a lifetime of about two Earth years. A set of 3-component broadband and short period seismometers (collectively known as SEIS) will be deployed beside the lander. In additional, InSight will also deploy a heat flow probe (HP3), a geodetic experiment (RISE), a magnetometer, and meteorological sensors. Seismological investigations of Mars have so far been based on modeling and synthetic data; starting in 2018, waveform data will be returned from Mars and the era of 'Seismology on Mars' will begin.

Building on our expertise and infrastructure for earthquake monitoring and seismic data processing on Earth, the SED will take the lead role in the building a catalogue of seismic events recorded by SEIS (the 'Marsquake Service’). This service will comprise automatic and reviewed event detection and characterization of local and teleseismic events, as well as meteor impacts. The goal of this service is to provide a comprehensive high-quality event catalogue for Mars that is critical to the SEIS project, in particular as input to the development of Martian crustal and deep structure models.

We are adapting advanced single-seismometer analysis techniques developed on the Earth to provide locations for Martian seismicity. Creating the Marsquake Service is a collaboration between the SED and the SEG groups at the ETH Zurich.

SED installed 3 seismological stations in the surroundings of the Mont Terri rock laboratory (St Ursanne, Canton Jura): 2 in the tunnel (stations MTI01 and MTI02) and 1 at the surface (MTI03). The Engineering Seismology group is in charge of the site characterization of these 3 stations. Therefore, a literature review and geophysical experiments are performed in order to propose velocity models able to reproduce the ground motion observed at these stations.

Since 2009, the Swiss Seismological Service is renewing and expanding its strong motion network. During the first phase, a total of 30 new accelerometer stations have been installed between 2009 and 2013, both replacing existing strong motion dial-up stations and installing new stations. During the ongoing second phase, 70 more stations are planned to be installed by 2019, including 4 borehole installations. The renewal project of the Swiss Strong Motion Network was approved by the Swiss Federal Council in February 2009. The project is monitored and supervised by a steering committee headed by the Swiss Federal Office for the Environment (FOEN).

The goals of the enlargement of the Swiss strong motion network are a better spatial coverage of earthquake prone regions, a better understanding of site-effects and thus the verification and improvement of hazard models. The epicentral areas of relevant past earthquakes have been instrumented in the first phase, namely Aigle (1584), Glarus (1971), Sarnen (1964), Sion-Sierre (1946), Yverdon (1929), Visp (1855), St. Gallen Rhine Valley (1796/96), Altdorf (1774), Brig (1755), Basel (1356), Churwalden/Vaz (1295/1991), etc. Further, the city areas of Zürich, Geneva, Basel, Bern, Lausanne, St. Gallen, Lucerne, Sion, Solothurn, Locarno, Chur, Sierre are relevant sites for free-field installation.

In the second phase, additional epicentral areas of past earthquakes are targeted, Churwalden (1295), Ardez (1504), Ardon (1524), Arbon (1720), Kreuzlingen (1911), and Moudon (1933), among others. Further urban areas are instrumented as well, e.g. Biel, Fribourg, Neuchâtel, Thun, Winterthur.

The site selection is always a trade-off between the scientific objectives and the level of vibration disturbances. Modern stations are sensitive enough to record also small earthquakes, but the signal-to-noise ratio may be too low due to traffic and industries. At all sites, geophysical measurements are performed to characterize the site response. Recorded signals can then be interpreted, and sites classified according to the amplification at the site, which is basic information for improved site-specific seismic hazard studies.

Ziel dieses Projekts ist die historisch-kritische Überarbeitung des Erdbebenkatalogs der Schweiz für die vorinstrumentelle und die frühe instrumentelle Periode der systematischen Erdbebenüberwachung (1878–1963). Entscheidend für eine möglichst korrekte Interpretation der Informationen aus verschiedenartigen Quellen ist, dass diese mittels geschichtswissenschaftlicher Methoden in ihren soziokulturellen Produktionskontext gestellt werden.

Kern der Arbeiten bildet die Aufarbeitung der Überlieferung von Erdbebenereignissen und die Einschätzung der Zuverlässigkeit der Informationsquellen. Weiter werden die makroseismischen Intensitätsfelder für mittelstarke Erdbeben, d. h. Ereignisse mit Epizentral-Intensitäten von IV bis VI auf der 12-stufigen Europäischen Makroseismischen Skala (EMS-98), rekonstruiert. Daraus lassen sich mittels einer in diesem Projekt weiterentwickelten kalibrierten Methode die Ereignisparameter, wie Magnitude, Lokalisierung und Herdtiefe, ableiten. Diese Ergebnisse werden zudem mit der Auswertung historischer Seismogramme abgeglichen.

Die mittelstarken Erdbeben des 19. und 20. Jahrhunderts sind von besonderer Relevanz. Da sie in der Schweiz vergleichsweise häufig auftreten und die Produktion verwertbarer Quellen in dieser Zeitperiode stark zunimmt, ergibt sich ein grosser Datensatz. Dieser erlaubt uns, unseren Kenntnisstand der Seismizität in der Schweiz zu verbessern und die Unsicherheiten zukünftiger Gefährdungs- und Risikostudien zu verkleinern. An der Schnittstelle zwischen Natur- und Geisteswissenschaft ist die Untersuchung der wissenschaftlichen Praktiken zur Produktion von Erdbebendaten auch von Interesse für diverse anderer Forschungsfelder, wie etwa die Wissens-, Umwelt- und Technikgeschichte oder die Risikosoziologie.

The second phase of this project (previously refered to "Expertengruppe Starkbeben") is split into 2 subtasks with the main goal to improve regional and local seismic hazard assessment in Switzerland; with particular focus to the sites of potential regions of nuclear repositories. These sub-projects are:

Subproject 1 aims to improve models and develop methods for the prediction of strong ground motion in Switzerland at the surface and at depth. Two main approaches are investigated: ground motion prediction equations (GMPEs) and stochastic simulation models. Both approaches require calibration to the local seismicity and careful consideration of their extrapolation to large magnitude events which have, as yet, not been instrumentally recorded in Switzerland. We use recordings of local seismicity in addition to numerical modelling results (subproject 2) to calibrate the predictive models for use in engineering practice.

Subproject 2 is focused on earthquake scenario modeling for Switzerland and exploration of the physical limits on ground motion. Our modeling combines realistic dynamic rupture along irregular fault surfaces and wave propagation in complex heterogeneous media at high frequency. Moreover we investigate the plastic and non-linear behavior of soft sediments at the Earth surface, conducting CPT measurements to calibrate our numerical models.

Subproject 3 focuses on numerical modeling the induced seismicity during tunnel excavation. Simulations will be performed using both thermo-hydro-mechanical coupled model and statistical model. We will investigate the risk of inducing seismicity during short-term active tunnel excavation and at later time. Numerical simulation will be also performed to match the fault slip experiment at Mont Terri. Finally, the results will be used as input for Subproject 1 and 2.

This group gathers the researchers with competences in site characterization in order to discuss and improve the work performed for different projects involving site characterization, especially for sites with new seismic stations. The available tools for processing, archiving and disseminating are shared within the group. The group is responsible for setting up and filling the SED database for site characterization. A process of review has been established in order to validate the work done before it is made public.

The group reviewed the 30 sites of the SSMNet Renewal phase 1, 6 sites of SSMNet stations in Basel installed in the frame of the Basel Erdbebenvorsorge project, the 10 sites of the NAGRA Network, the installation site of stations in the area of the Mont Terri rock laboratory, 2 sites of SSMNet stations in Liechtenstein and the currently installed sites of the SSMNet Renewal Phase 2.

Within this project, new signal processing techniques for the analysis of ambient vibrations are developed. The focus is on the development of single-station methods and the adaptation of existing techniques to large arrays.

Single-station methods represent an extremely valuable tool. The use of a single station further simplifies the measurement procedure thus enabling a more time and cost effective survey.

Assumptions on the wavefield used when processing small arrays may be no longer valid when analyzing large arrays. For this reason, we investigate adaptations of existing techniques to large arrays.

Target applications of the methods developed within this project include microzonation studies in Switzerland and investigation of the characteristics of the Swiss Molasse Basin.

Recent discoveries include: Non-volcanic tremors (NVT), strong heterogeneity of the relative stress distribution, temporal and along-fault variable aseismic creep, repeating earthquakes, slow slip events. Based on the insight that was gained from these previous studies, we will be able to develop and calibrate an indicative stress-meter for the Earth’s crust. In this project we link for the first time the statistical analysis of the size distribution of earthquakes with complementary observations of fault movement.

This yields an improved understanding of the nature of fault loading cycles. Therefore, the results will provide key understanding to unravelling the predictability of earthquakes and has the potential to radically change the assessment of local seismic hazard for selected well-understood and well-monitored faults.

Quantifying time-varying seismicity rates is fundamentally important to protecting people who live in areas subject to extreme earthquake shaking. One primary difficulty with such assessment is determining how faults interact. Some recent studies have noted the ability of passing earthquake waves to increase the 'triggerability' of a fault in a delayed form of dynamic stressing: after seismic waves pass, faults are more prone to fail in a subsequent earthquake. The deadly Canterbury earthquake sequence has characteristics that suggest it was promoted by such distant, delayed, dynamic triggering. The sequence is also compatible with a model in which low-strain rate areas are efficient at storing and transferring static stresses. This has implications for earthquake clustering and the generation of damaging ground motion. We will apply recently-developed techniques in concert to address three questions: 1) Can we quantify distant and delayed triggering in this sequence? We will address this by correlating increased geodetic crustal velocities in Canterbury following the 2009 M7.8 Dusky Sound earthquake that occurred hundreds of km away. We will apply source scanning and template matching techniques to search Canterbury for microseismicity that was triggered by the M7.8 event. 2) Do earthquakes in low-strain rate areas exhibit more clustering and longer aftershock sequences than their high-strain rate counterparts, and do these earthquakes produce stronger ground motions? We will build a comprehensive model of earthquake generation in low-strain rate areas by using an earthquake simulator to model the evolution of the sequence. 3) Can the simulator model we develop demonstrate skill in seismicity forecast experiments? The model developed in this project could provide a true step change and bring seismology closer to bridging the gap between probabilistic forecasting and deterministic modelling of earthquake hazard.

Our present knowledge about earthquakes does not yet allow us to reliably forecast earthquakes. Therefore, the study of precursors is an essential step in the direction of earthquake forecasting. Precursors can be anomalous seismic patterns or other phenomena such as peculiar animal behavior, or electromagnetic anomalies etc., which indicate the incidence of a large event. We focus in our studies on seismic precursors, namely quiescence, which is expressed through reduced seismic activity, accelerated seismicity (ASR) and short term foreshocks. The mentioned precursors are observed in many selected earthquake sequences in the past. However, there is skepticism if these precursors happen systematically; some studies explain their occurrence rather as a random temporary perturbation of normal seismicity which is accidentally followed by a large earthquake.

We believe that systematic investigations on the occurrence of precursors give essential evidence for or against their existence. We chose to perform these investigations with statistical tools, hence by evaluating location, time and magnitudes of earthquakes from several regional earthquake catalogs of the world, to obtain representative precursor statistics.

We find that small earthquakes, as they occur more frequently, could facilitate the detection of precursory patterns (Mignan, 2014). We study statistical models used to describe earthquake occurrence and the impact of the choice of the lowest magnitude on them (Seif et al, 2016, submitted). Using these models we evaluate if foreshock occurrence differs from normal seismicity. We also want to specify how often foreshock patterns are followed by large events or not (true/false alarm rate). In the future remaining precursory patterns, quiescence and accelerated seismicity, will be investigated in the same way. We hope that the statistical analysis will allow us to better understand the physical processes which lead to the occurrence of precursors.

Statistical seismology is the application of rigorous statistical methods to earthquake science with the goal of improving our knowledge of how the earth works. Within statistical seismology there is a strong emphasis on the analysis of seismicity data in order to improve our scientific understanding of earthquakes and to improve the evaluation and testing of earthquake forecasts, earthquake early warning, and seismic hazards assessments. Given the societal importance of these applications, statistical seismology must be done well. Unfortunately, a lack of educational resources and available software tools make it difficult for students and new practitioners to learn about this discipline. The goal of the Community Online Resource for Statistical Seismicity Analysis (CORSSA) is to promote excellence in statistical seismology by providing the knowledge and resources necessary to understand and implement the best practices.

CORSSA covers a wide variety of themes:

Introductory Material
Statistical Foundations
Understanding Seismicity Catalogs and Their Problems
Models and Techniques for Analyzing Seismicity
Earthquake Predictability and Related Hypothesis Testing

Each of these themes includes a series of articles that are listed in the CORSSA Table of Contents. The series of themes was devised to make it easy for the reader to focus on their personal requirements to get an introduction to statistical seismology, or to learn about the basics of earthquakes, statistics, and/or the intricacies of seismicity catalogs before moving onto applications.

This is the 1st subproject of the „ENSI – SED-Erdbebenforschung zu Schweizer Kernanlagen“ project.

This subproject aims to improve source-scaling and attenuation models and to develop methods for the prediction of strong ground motion in Switzerland both at the surface as well as at depth. Two main approaches are investigated: ground motion prediction equations (GMPEs) and stochastic simulation models. Both approaches require adaptions to the local seismicity and careful consideration of their calibration to Swiss conditions. The stochastic model corresponds to the current state of research and has some advantages over the empirical attenuation relationships, as it is possible to adjust the model to specific local site conditions. The complete understanding in terms of physical parameterization of such models is crucial in order to decouple different effects, which allow building robust predictive models that scale appropriately to large magnitude events. To this regard, a model from Japanese data is now being developed that will allow the review of the Swiss model for large magnitudes in the different distance ranges and at various rock sites which have, as yet, not been instrumentally recorded in Switzerland. Moreover, we will use recordings of local seismicity in addition to numerical modeling results of related projects to calibrate the predictive models. The long-term goal is to develop an improved stochastic simulation model for Switzerland allowing existing uncertainties to be reduced. In future, such models will also allow an assessment of ground motion caused by induced seismicity due to the activation of existing fractures and/or the generation of new fractures.

This is the 2nd subproject of the „ENSI – SED-Erdbebenforschung zu Schweizer Kernanlagen“ project.

Realistic modeling of earthquake ground motions can be achieved only if the causative fault and the medium where waves propagate are described accurately. In earthquake scenario simulations for Switzerland, we combine state-of-the-art dynamic rupture along irregular fault surfaces and wave propagation in complex heterogeneous media at high frequency. Besides ordinary faulting due to accumulation of tectonic stress, we consider fault rupture induced by human activities, such as fluid injection. In such broadband simulations, the interaction between the seismic wave field and the medium occurs at multiple levels and scales. Therefore, we couple high-resolution 3D basin models with random velocity heterogeneity and complex topography to correctly model resonance, mode conversion and scattering of seismic waves. Along with source and path effects, near-surface site conditions represent an important factor controlling ground motions since soft sediments can significantly amplify the shaking observed during an earthquake. Depending on the level of input ground motion, liquefiable soils have the potential to generate excess water pressure resulting in high-frequency acceleration pulses. Advanced constitutive models of liquefiable soils require the knowledge of so-called dilatancy parameters that describe the potential to generate excess water pressure. These parameters can be determined from field observations by analyzing cone penetration test (CPT) measurements. Accurate modeling of liquefiable soils is essential to reliable prediction of earthquake site response and can help explore the physical limits of ground motion.