Earthquakes in Switzerland and surrounding regions during 2013

This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during 2013. During this period, 699 earthquakes and 208 quarry blasts were detected and located in the region under consideration. With a total of 18 events with local magnitudes ML ≥ 2.5, the seismic activity in the year 2013 was slightly below the average over the previous 38years. Most noteworthy were the two earthquake sequences of St. Gallen (SG) in July and Balzers (FL) in December. The former was induced by reservoir stimulation operations at the St. Gallen geothermal project. The maximum local magnitude in the sequence was 3.5, comparable in size with the ML 3.4 event induced by stimulation operations below Basel in 2006. The sequence of Balzers was associated with an ML 4.1 earthquake in the border region to Liechtenstein. More than 30 aftershocks with magnitudes ranging between ML −0.2 and ML 3.7 were detected in the month following the mainshock. The ML 3.5 St. Gallen and the ML 4.1 Balzers earthquakes were widely felt by the public but no reports on damages are known. The maximum intensity for both events was IV

Earthquakes in Switzerland and surrounding regions during 2013

This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during 2013. During this period, 699 earthquakes and 208 quarry blasts were detected and located in the region under consideration. With a total of 18 events with local magnitudes ML ≥ 2.5, the seismic activity in the year 2013 was slightly below the average over the previous 38years. Most noteworthy were the two earthquake sequences of St. Gallen (SG) in July and Balzers (FL) in December. The former was induced by reservoir stimulation operations at the St. Gallen geothermal project. The maximum local magnitude in the sequence was 3.5, comparable in size with the ML 3.4 event induced by stimulation operations below Basel in 2006. The sequence of Balzers was associated with an ML 4.1 earthquake in the border region to Liechtenstein. More than 30 aftershocks with magnitudes ranging between ML −0.2 and ML 3.7 were detected in the month following the mainshock. The ML 3.5 St. Gallen and the ML 4.1 Balzers earthquakes were widely felt by the public but no reports on damages are known. The maximum intensity for both events was IV

Earthquakes in Switzerland and surrounding regions during 2012

This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during 2012. During this period, 497 earthquakes and 88 quarry blasts were detected and located in the region under consideration. With a total of only 13 events with ML≥2.5, the seismic activity in the year 2012 was far below the average over the previous 37years. Most noteworthy were the earthquake sequence of Filisur (GR) in January with two events of ML 3.3 and 3.5, the ML 4.2 and ML 3.5 earthquakes at a depth of 32km below Zug in February and the ML 3.6 event near Vallorcine in October. The epicentral intensity of the ML 4.2 event close to Zug was IV, with a maximum intensity of V reached in a few areas, probably due to site amplification effect

Fixing the rotating-wave approximation for strongly detuned quantum oscillators

Periodically driven oscillators are commonly described in a frame corotating with the drive and using the rotating-wave approximation (RWA). This description, however, is known to induce errors for off-resonant driving. Here, we show that the standard quantum description, using the creation and annihilation of particles with the oscillators' natural frequency, necessarily leads to incorrect results when combined with the RWA. We demonstrate this on the simple (quantum) harmonic oscillator and present an alternative operator basis that reconciles the RWA with off-resonant driving. The approach is also applicable to more complex models, where it accounts for known discrepancies. As an example, we demonstrate the advantage of our scheme on a driven quantum Duffing oscillator.ISSN:2643-156

SCDetect: Near real-time computationally efficient waveform cross-correlation based earthquake detection during intense earthquake sequences

Aftershock sequences or earthquake swarms generate a high number of seismic events that are not detected by standard regional network routine processes. Undetected earthquakes are mostly due to low signal to noise ratio, overlapping earthquakes, and a network configuration that targets earthquake detection with a homogeneous magnitude of completeness. Furthermore, the analyst’s workload is increasing dramatically during an intense earthquake sequence, which results in prompt manual review of the largest events, only. We present a computationally efficient and highly customizable tool (SCDetect) to detect earthquakes in near real-time by applying waveform cross-correlation in the time domain based on a set of template events. SCDetect is a free and open-source SeisComP extension module fully integrated into the SeisComP environment. It may be used to process both archived waveform data, when operated in playback mode, as well as real-time data. In either of the use cases, waveform data is accessed through SeisComP’s standard RecordStream interface. Multiple template event based detectors may be configured. The individual detector configuration is fully stream based which allows for generic multi-stream event detection. Event parameter products for newly detected events (i.e. origins, picks, amplitudes, station magnitudes) may be sent to SeisComP's messaging system for further processing. In addition to earthquake detection, we implement amplitude calculation by measuring amplitudes on the horizontal components. SCDetect offers multiple magnitude estimation methods based on the amplitudes of the template earthquakes and the new detections (i.e regression, amplitude ratios). Magnitude estimation is configurable using SeisComP’s bindings configuration. We applied SCDetect to recent earthquake sequences in Switzerland between 2019 and 2021. The dense seismic network operated by the Swiss Seismological Service offers a unique opportunity to evaluate the performance of the proposed module. Our first results show that these extended earthquake catalogs contain at least ten times more earthquakes than the national earthquake catalogue

Updated determination of earthquake magnitudes at the Swiss Seismological Service

The Swiss Seismological Service (SED; http://www.seismo.ethz.ch) at ETH Zürich is the federal agency in charge of monitoring earthquakes in Switzerland and neighboring areas, and for the assessment of seismic hazard and risk for the region. The SED seismic network largely relies on software and databases integrated in the SeisComP3 monitoring suite for waveform acquisition, automatic and manual event processing, event alerting, web infrastructure, data archiving and dissemination. Data from all digital seismic stations acquired by the SED over the last 30 years - broadband (presently ~230), strong-motion (~185), short-period (~65), permanent and temporary - are homogeneously integrated in the seismic network processing tools and products. Waveform data from the Swiss National Seismic Networks are openly available through the SED website and ORFEUS EIDA / Strong-Motion (http://orfeus-eu.org/data/) data gateways. The SED earthquake catalogue is publicly available through FDSN Event web services at the SED (http://arclink.ethz.ch/fdsnws/event/1/). The Swiss seismic hazard maps are integrated in the EFEHR portal (http://www.efehr.org). The SED is updating its strategy for magnitude determination to make it fully consistent with the state-of-the-art in engineering seismology and seismic hazard studies in Switzerland, and to optimise the use of its dense seismic monitoring infrastructure. Among the planned changes are the: (a) adoption of a new ML relationship applicable in the near-source region at epicentral distances smaller than 15-20 km; (b) inclusion of ML station corrections based on empirically observed (de)amplification with respect to the Swiss reference rock velocity model and associated predictions; (c) seamless computation of Mw based on spectral fitting of recorded FAS using a Swiss specific model. In this contribution we present and discuss the updated magnitude computations for a playback dataset of thousands of recorded earthquakes, and compare them with the current official estimates. We discuss the expected impacts of the new magnitude determination strategy on the SED event processing chain in SeisComP3, the SED catalogues and other seismological products. We welcome community feedback on our planned transition strategy

Earthquakes in Switzerland and surrounding regions during 2013

This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during 2013. During this period, 699 earthquakes and 208 quarry blasts were detected and located in the region under consideration. With a total of 18 events with local magnitudes ML ≥ 2.5, the seismic activity in the year 2013 was slightly below the average over the previous 38 years. Most noteworthy were the two earthquake sequences of St. Gallen (SG) in July and Balzers (FL) in December. The former was induced by reservoir stimulation operations at the St. Gallen geothermal project. The maximum local magnitude in the sequence was 3.5, comparable in size with the ML 3.4 event induced by stimulation operations below Basel in 2006. The sequence of Balzers was associated with an ML 4.1 earthquake in the border region to Liechtenstein. More than 30 aftershocks with magnitudes ranging between ML −0.2 and ML 3.7 were detected in the month following the mainshock. The ML 3.5 St. Gallen and the ML 4.1 Balzers earthquakes were widely felt by the public but no reports on damages are known. The maximum intensity for both events was IV.ISSN:1661-8734ISSN:1661-872

Earthquakes in Switzerland and surrounding regions during 2015 and 2016

This report summarizes the seismicity in Switzerland and surrounding regions in the years 2015 and 2016. In 2015, the Swiss Seismological Service detected and located 735 earthquakes in the region under consideration. With a total of 20 earthquakes of magnitude ML ≥ 2.5, the seismic activity of potentially felt events in 2015 was close to the average of 23 earthquakes over the previous 40 years. Seismic activity was above average in 2016 with 872 located earthquakes of which 31 events had ML ≥ 2.5. The strongest event in the analyzed period was the ML 4.1 Salgesch earthquake, which occurred northeast of Sierre (VS) in October 2016. The event was felt in large parts of Switzerland and had a maximum intensity of V. Derived focal mechanisms and relative hypocenter relocations of aftershocks image a SSE dipping reverse fault, which likely also hosted an ML 3.9 earthquake in 2003. Another remarkable earthquake sequence in the Valais occurred close to Sion with four felt events (ML 2.7–3.2) in 2015/16. We associate this sequence with a system of WNW-ESE striking fault segments north of the Rhône valley. Similarities with a sequence in 2011, which was located about 10 km to the NE, suggest the existence of an en-echelon system of basement faults accommodating dextral slip along the Rhône-Simplon line in this area. Another exceptional earthquake sequence occurred close to Singen (Germany) in November 2016. Relocated hypocenters and focal mechanisms image a SW dipping transtensional fault segment, which is likely associated with a branch of the Hegau-Bodensee Graben. On the western boundary of this graben, micro-earthquakes close to Schlattingen (TG) in 2015/16 are possibly related to a NE dipping branch of the Neuhausen Fault. Other cases of earthquakes felt by the public during 2015/16 include earthquakes in the region of Biel, Vallorcine, Solothurn, and Savognin.ISSN:1661-8734ISSN:1661-872

Earthquakes in Switzerland and surrounding regions during 2014

During 2014, 817 earthquakes and 180 quarry blasts were detected and located in the region under consideration. An additional 160 earthquakes with ML≤1.0 were located using supplementary analysis techniques. The number of located earthquakes in 2014 was the largest since the installation of a seismic network in Switzerland in 1975. This unusually large number is mainly due to the occurrence of two vigorous earthquake sequences, and the local reduction of the earthquake detection thresholds of the Swiss seismic network. With a total of 22 earthquakes of ML≥2.5, the seismic activity of larger and potentially felt events was close to the average of 23 earthquakes over the previous 39years. The most noteworthy seismicity was the earthquake sequence near Diemtigen, west of Lake Thun, where more than 270 events were located between April and December. High-precision hypocenter relocation was applied to image the spatio-temporal evolution of this seismicity. The sequence culminated in an M L 3.2 event in October, which was felt in the region of Lake Thun and Bern. Other cases of earthquakes felt by the public include earthquakes in the region of Biel (ML 3.2), in Vallorcine (ML 3.2), and in Stalden (ML 3.0). Finally, a small but unusually deep earthquake was recorded beneath the Jura Mountains. Focal depth, apparent velocities, as well as waveform characteristics of this earthquake are consistent with a source in the uppermost mantle. This earthquake is the first reliable record of a sub-Moho event ever observed in Switzerland. Zusammenfassung: Dieser Bericht des Schweizerischen Erdbebendienstes stellt eine Zusammenfassung der im Vorjahr in der Schweiz und Umgebung aufgetretenen Erdbeben dar. Im Jahr 2014 wurden im erwähnten Gebiet 817 Erdbeben sowie 180 Sprengungen erfasst und lokalisiert. Weitere 160 Beben mit Magnituden ML≤1.0 wurden mit Hilfe von zusätzlichen Auswertungsmethoden lokalisiert. Die Zahl der in 2014 lokalisierten Erdbeben ist die höchste seit der Installation eines seismischen Messnetzes in der Schweiz im Jahre 1975. Diese außergewöhnlich hohe Zahl erklärt sich vor allem durch das Auftreten zweier äußerst aktiver Erdbebensequenzen und der lokalen Absenkung der Detektionsschwelle für Erdbeben durch die Verbesserung des seismischen Messnetzes der Schweiz. Mit 22 Beben der Magnitude ML≥2.5 lag die seismische Aktivität von stärkeren und potentiell spürbaren Ereignissen im Jahr 2014 nahe am Durchschnitt von 23 Beben pro Jahr der vergangenen 39 Jahren. Bemerkenswert war die Erdbebensequenz von Diemtigen, westlich vom Thunersee bei der mehr als 270 Ereignisse zwischen April und Dezember lokalisiert wurden. Hochauflösende Erdbebenlokalisierung wurde verwendet, um die räumliche und zeitliche Entwicklung dieser Erdbebenserie abzubilden. Ein Beben der Magnitude ML 3.2 bildete den Höhepunkt der Sequenz im Oktober. Dieses wurde in der Region des Thunersees und Bern deutlich verspürt. Weitere Erdbeben, die von der Bevölkerung verspürt wurden, waren unter anderem die Beben in der Region Biel (ML 3.2), in Vallorcine (ML 3.2) und in Stalden (ML 3.0). Darüberhinaus wurde ein schwaches, aber ungewöhnlich tiefes Erdbeben unterhalb des Juras registriert. Sowohl Herdtiefe, Scheingeschwindigkeiten und Charakter der Wellenformen weisen auf einen Erdbebenherd im obersten Mantel hin. Damit ist dieses Ereignis die erste verlässliche Beobachtung eines Erdbebens unterhalb der Moho in der Schweiz. Resumé: Ce rapport du Service Sismologique Suisse résume l'activité sismique en Suisse et dans ses régions environnantes au cours de l'année 2014. Pendant cette période, 817 tremblements de terre et 180 tirs de carrière ont été détectés et localisés dans la région. 160séismes additionnels de magnitude ML≤1.0 ont été localisés à l'aide de moyens supplémentaires d'analyse. Le nombre des évènements localisés en 2014 constitue un record depuis 1975, date de l'installation du réseau sismologique en Suisse. Ce grand nombre inhabituel peut être principalement expliqué par l'occurrence de deux séquences sismiques importantes et par la diminution locale des niveaux de détection résultant des améliorations apportées au réseau sismologique suisse. Avec un total de 22séismes de magnitude ML≥2.5, le nombre des évènements les plus forts et potentiellement ressentis est proche de la moyenne annuelle de 23 tremblements de terre enregistrée pendant les 39 dernières années. La sismicité la plus notable est la séquence sismique qui a eu lieu près de Diemtigen, à l'ouest du lac de Thoune, où plus de 270 évènements ont été localisés entre avril et décembre. La relocalisation de grande précision des hypocentres a permis d'imager l'évolution spatio-temporelle de cette sismicité. La séquence est dominée par un séisme de magnitude ML 3.2 en octobre qui a été ressenti dans la région du lac de Thoune et à Berne. D'autres tremblements de terre ont été ressentis par la population, tels que ceux de la région de Bienne (ML 3.2), de Vallorcine (ML 3.2) et de Stalden (ML 3.0). Enfin, un faible mais inhabituel séisme profond a été enregistré dans le Jura. Sa profondeur focale, les vitesses apparentes enregistrées ainsi que les caractéristiques des formes d'ondes de ce tremblement de terre sont en accord avec une source dans le manteau supérieur. Par conséquence, ce tremblement de terre est le premier enregistrement fiable d'un évènement ayant eu lieu sous le Moho en Suisse