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The Finnish National Seismic Network

The Institute of Seismology, University of Helsinki (ISUH) was founded in 1961 as a response to the growing public concern for environmental hazards caused by nuclear weapon testing. Since then ISUH has been responsible for seismic monitoring in Finland. The current mandate covers government regulator duties in seismic hazard mitigation and nuclear test ban treaty verification, observatory activities and operation of the Finnish National Seismic Network (FNSN) as well as research and teaching of seismology at the University of Helsinki.The first seismograph station of Finland was installed at the premises of the Department of Physics, University of Helsinki in 1924. However, the mechanical Mainka seismographs had low magnification and thus the recordings were of little practical value for the study of local seismicity. The first short-period seismographs were set up between 1956 and 1963. The next significant upgrade of FNSN occurred during the late 1970’s when digital tripartite arrays in southern and central Finland became fully operational, allowing for systematic use of instrumental detection, location and magnitude determination methods. By the end of the 1990’s, the entire network was operating using digital telemetric or dial-up methods. The FNSN has expanded significantly during the 21st Century. It comprises now 36 permanent stations. Most of the stations have Streckeisen STS-2, Nanometrics Trillium (Compact/P/PA/QA) or Guralp CMG-3T broad band sensors. Some Teledyne-Geotech S13/GS13 short period sensors are also in use. Data acquisition systems are a combination of Earth Data PS6-24 digitizers and PC with Seiscomp/Seedlink software or Nanometrics Centaurs. The stations are connected to the ISUH with Seedlink via Internet and provide continuous waveform data at 40 Hz (array) or 100-250 Hz sampling frequency. Further information about instrumentation can be found at the Institute’s web site (www.seismo.helsinki.fi). Waveform data are available from the GEOFON data centre, under network code HE, and arefully open.

Seismological experiment at Strokkur from 2020

Seismological experiment at Strokkur from 2020" is a seismological experiment realized at the most active geyser on Iceland by Eva Eibl (University of Potsdam) in collaboration with Gylfi P. Hersir formerly at ISOR Iceland. The geyser is part of the Haukadalur geothermal area in south Iceland, which contains numerous geothermal anomalies, hot springs, and basins (Walter et al., 2018). Strokkur is a pool geyser and has a silica sinter edifice with a water basin on top, which is about 12m in diameter with a central tube of more than 20m depth. The aim of the seismic experiment is to monitor eruptions of Strokkur geyser from March 2020 using three broadband seismic stations (Nanometrics Trillium Compact 120s). Sensors were buried at distances of 38.8m (GE4, SE), 47.3m (GE3, SW), and 42.5m (GE2, N) from Strokkur center. Within this time period about 1 month of data is missing due to power outages. At any other times at least one station recorded the eruptions. From this dataset, converted to MSEED using Pyrocko, currently a catalogue of 506,131 water fountains was determined and further investigated in Eibl et al. (2025). In addition, Eibl et al. (2025) assessed the effect of the weather on the system including the bubble trap suspected at around 24 m depth by Eibl et al. (2021). Waveform data are available from the GEOFON data centre, under network code 2Z.

Seismological Characterization of the Geothermal Field Laboratory Rhineland

– A temporary seismic network consisting of 48 long-term and 15 short-term stations was deployed from June 2021 to June 2022. The network comprises 27 broadband stations and 20 short period geophones from the Ruhr-University Bochum, the Geophysical Instrument Pool Potsdam (GIPP) and the RWTH Aachen. The inter-station spacing of the longer-term network is about 2 km and the total extent of the network is about 20 km. The densely populated area and vicinity of active pit mining demanded a balance between dense station placement and avoidance of anthropogenic noise sources. The network serves as a pre-study for the installment of a field laboratory in Eschweiler-Weisweiler, Germany. Details can be found in the accompanying data publication (Finger et al., in preparation). This project has been subsidized through the Cofund GEOTHERMICA, which is supported by the European Union’s HORIZON 2020 programme for research, technological development and demonstration under grant agreement No 731117. Furthermore, this study was supported by the Interreg North-West Europe (Interreg NWE) Programme through the Roll-out of Deep Geothermal Energy in North-West Europe (DGE-ROLLOUT) Project (http://www.nweurope.eu/DGE-Rollout), NWE 892. The Interreg NWE Programme is part of the European Cohesion Policy and is financed by the European Regional Development Fund (ERDF). Waveform data are available from the GEOFON data centre, under network code ZB. Data from embargoed stations might be available on request.

Estonian National Seismic Network (EESN)

The Geological Survey of Estonia (EGT) maintains the Estonian National Seismic Network (EESN) under the network code EE. EGT is responsible of seismic monitoring of Estonia as a part of the national environmental monitoring program. Routine seismic analysis is performed in integrated co-operation with the Institute of Seismology, University of Helsinki (ISUH), and detected events are published in ISUH bulletins. The network dates back from 1980 and digital data exist from 1996 on. Initially, only one to three stations were operational. From 2015 on, the network has been expanded using temporary stations. By 2025, eight permanent and two temporary EE stations operate in real time. VSU is a joint station with GEOFON, labelled both as a GE and an EE station. Three older Estonian stations are equipped with Streckeisen STS-2 and Güralp CMG-6T seismometers. Newer sites have Nanometrics Trillium Compact sensors. Data acquisition systems are a combination of Earth Data digitizers and PC with Seiscomp software or Nanometrics Centaurs. Data sampling frequencies are 100 Hz or 250 Hz. Waveform data under network code EE are available from the GEOFON data centre and are fully open.

Seismic array data for monitoring and tracking tremor sources during subglacial floods and volcanic eruptions at Vatnajökull (Vatna Glacier), Iceland

As part of project FUTUREVOLC, European volcanological supersite in Iceland: a monitoring system and network for the future, two 7-element seismic broadband arrays were installed outside the western margin of Vatnajökull glacier, Iceland. The goal was to study seismic tremor associated with floods originating in the eastern and western Skaftár cauldrons. A third temporary array was installed during the Bárðarbunga 2014-2015 volcanic eruption near the eruption site. The aim of the array installations was to discriminate between different seismic tremor sources, namely volcanic eruptions, lava flows, hydrothermal explosions and subglacial floods (jökulhlaups). The main aim of the two arrays installed on the western margin of Vatnajökull was to study their early-warning potential through the analysis of four subglacial floods observed during the study period. The seismic vibrations associated with these floods have an emergent start, are of long duration and are referred to as tremor or high-frequency noise. Due to the lack of clear discrete onsets they cannot be located using traditional earthquake location methods. Instead clusters of seismometers (called arrays) are employed to both locate the tremor source and determine the wave type in the tremor (surface vs. body waves). The array data recorded during the Bárðarbunga eruption were used to investigate the nature of shallow, pre-eruptive, long-duration seismic tremor activity related to shallow dyke formation. The sources of the tremor were found to locate at the eruption site and under ice cauldrons which formed on the ice surface during the first weeks of the unrest. Waveform data are available from the GEOFON data centre, under network code 5L.

Cliff coast failures on the Jasmund part of Rügen, Germany

Cliffs line many erosional coastlines. Localized failures can cause land loss and hazard, and impact ecosystems and sediment routing. Links between cliff erosion and forcing mechanisms are poorly constrained, due to limitations of classic approaches. Combining multi-seasonal seismic and drone surveys, wave, precipitation and groundwater data we study drivers and triggers of seismically detected failures along the chalk cliffs on Germany's largest island, Rügen. The network consists of four (later five) seismic stations along the 8.6 km long chalk cliff coast. Waveform data are available from the GEOFON data centre, under network code 4K.

1 year seismological experiment at Strokkur in 2017/18

Strokkur_1yr is a one year seismological experiment realized at the most active geyser on Iceland by Eva Eibl (University of Potsdam) in collaboration with Thomas R. Walter, Phillippe Jousset, Torsten Dahm, Masoud Allahbakhshi, Daniel Müller from GFZ Potsdam and Gylfi P. Hersir from ISOR Iceland. The geyser is part of the Haukadalur geothermal area in south Iceland, which contains numerous geothermal anomalies, hot springs, and basins (Walter et al., 2018). Strokkur is a pool geyser and has a silica sinter edifice with a water basin on top, which is about 12 m in diameter with a central tube of more than 20 m depth. The aim of the seismic experiment is to monitor eruptions of Strokkur geyser from June 2017 to June 2018 using four broadband seismic stations (Nanometrics Trillium Compact Posthole 20 s). Sensors were buried 30–40 cm deep in the ground at distances of 38.8 m (G4, SE), 47.3 m (G3, SW), 42.5 m (G2, N), and 95.5 m (G1, NE) from Strokkur center. Data gaps represent 15–44 % of the records as during the winter period maintenance intervals were longer and battery drainage was high. However, at any given time, at least one station recorded the eruptions. From this dataset, converted to MSEED using Pyrocko, a catalogue of 70,000 eruptions was determined and further investigated in Eibl et al. (2020) Waveform data are available from the GEOFON data centre, under network code 7L.

Ketzin Seismic Monitoring Network

Ketzin in a small town 20km west of Berlin that hosts a research facility for underground storage. Starting in 2008 the site was used to investigate the onshore geological storage of carbon dioxide (Liebscher et al., 2013). Among a large variety of downhole monitoring measurements and repeated 3D seismics above the storage formation, a seismic network was installed to investigate the possibility of monitoring subsurface processes related to the injection of CO2 with passive seismic recordings (Gassenmeier et al., 2015). The network was operated for 12 month from early 2011 to 2012 and consisted of 10 Guralp broadband sensors of the Geophysical Instrument Pool Potsdam (GIPP). Five instruments were located at the drilling site and five instruments were installed at a distance up to 3.5km around the injection site. The Instruments were either installed in basements or buried at a depth of about 70cm (KTE, KTF and KTG). The installation was supported by the German Federal Ministry of Education and Research (BMBF, grant 03G0736A) by the University of Leipzig and the GIPP.

1 week seismological huddle test using 5 rotational sensors and 3 seismometers in August 2019

We provide seismological data from a huddle test in Fürstenfeldbruck in August 2019 that was realized by University of Potsdam (PI: Eva Eibl) in collaboration with BGR (PI: Stefanie Donner) and LMU (PI: Felix Bernauer). 5 rotational sensors (blueSeis-3A) and 3 seismometers (Trillium Horizon 120s Nanometrics) were installed on a decoupled basement in a building of the Geophysical Observatory Fürstenfeldbruck. The seismometers were isolated with black foam rubber and white cotton. We recorded passive seismological data for one week and recorded noise, coherent noise sources and the August 29, 2019 ML 3.4 Dettingen earthquake. The aim of the seismic experiment is to compare the performance of rotational sensors and seismometers with respect to different coherent and incoherent noise sources. The noise level, spectral content of the coherent noise and back azimuth of the Dettingen earthquake was further investigated for all sensors using correlation, coherence analysis and probabilistic power spectral densities in Izgi et al. (2021). Waveform data are available from the GEOFON data centre, under network code X3.

Mauritius Seismic Land Station

Broadband seismic station deployed in Mauritius under RHUM-RUM project. Waveform data are available from the GEOFON data centre, under network code 3E under CC-BY 4.0 license.

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