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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.

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.

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.

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.

Building Monitoring and Decentralized on-site Earthquake Early Warning network, Bishkek (Kyrgyzstan)

Building monitoring and decentralized, on-site Earthquake Early Warning system for the Kyrgyz capital Bishkek. Several low cost sensors equipped with MEMS accelerometers have been installed in eleven buildings within the urban area of the city. The different sensing units communicate with each other via wireless links and the seismic data are streamed in real-time to data centres at GFZ and the Central Asian Institute for Applied Geoscience (CAIAG) using internet. Since each sensing unit has its own computing capabilities, software for data processing can be installed to perform decentralised actions. In particular, each sensing unit can perform event detection tasks and run software for on-site early warning. If a description for the vulnerability of the building is uploaded to the sensing unit, this can be exploited to introduce the expected probability of damage in the early-warning protocol customized for a specific structure. Waveform data are available from the GEOFON data centre, under network code KD.

Kivu Seismological Network (KivuSnet)

KivuSNet represents the first dense broadband seismic network installed in the Kivu Rift region, which is located in the bordering region of the Democratic Republic of Congo and Rwanda. Here the active volcanoes Nyamulagira (the most active in Africa) and Nyiragongo (host to the largest persistent lava lake on Earth) threaten the city of Goma and neighbouring agglomerations, and destructive earthquakes can also affect the region. The deployement started with the first stations in 2012/2013 and since October 2015, 13 stations are operated with real-time data transmission. The development of KivuSNet has been carried out in the framework of several research projects and is in particular associated with the project REmote Sensing and In Situ detection and Tracking of geohazards (RESIST), funded by the Belgian Science Policy and the National Research Fund of Luxembourg. KivuSNet aims at opening a new window for the seismological knowledge in this highly active rifting region, allowing for unprecedented insights into tectonic and volcanic seismicity, tremor patterns and Earth structure as well as for sustainable real-time monitoring of the volcanoes in the area. Together with the often co-located KivuGNet geodetic stations, KivuSNet closes a dramatic observational gap in this region. Waveform data is available from the GEOFON data centre, under network code KV. Embargo policy: - All data before 1 August 2019 remain under embargo until 1 August 2024; - Data acquired from 1 August 2019 onwards are opened 3 years after their acquisition, progressively in 1-months batches (e.g. Data from August 2019 would be opened on 1 September 2022, data from September 2019 would be opened on 1 October 2022 etc.) - For any access request to data that are still under embargo, written permission of the RESIST project partners is needed.

Northern Finland Seismological Network

Sodankylä geophysical observatory (SGO) has operated in Sodankylä in northern Finland since 1913. SGO was originally founded by the Finnish Academy of Science and Letters. Now it takes care of national and international duties studying the space and geoenvironment as an independent research organisation in the University of Oulu. SGO performs long-term measurements, builds instruments, innovates and maintains domestic and international measurements, and performs research from these measurements. The seismic observations at SGO started in Sodankylä 1956. In 2005-2006 SGO seismic stations were updated to broadband instrumentation and connected to GEOFON data center. Today, the number of seismic stations has increased to 9. The stations have Streckeisen STS-2 or Nanometrics Trillium PA/PH broadband sensors. 3 of the stations are so called Posthole stations located in borehole 5-22 m below surface. The rest of the stations are located on the surface or in a more traditional type of vault. Data acquisition systems are either Earth Data PS6-24 digitisers and PC with Seiscomp or Nanometrics Centaurs. The continuous waveform data are collected at 100 Hz sampling frequency. The data are available from GEOFON data center. Further information about instrumentation can be found at the Institute’s web site (https://www.sgo.fi/). Waveform data are available from the GEOFON data centre, under network code FN, and arefully open.

MAGIC (Magma Iceland)

In January 2020, a swarm of earthquakes started under Thorbjorn volcano, Reykjanes, SW Iceland, associated to the uplift of up to 0.5 cm per day. Concern in Iceland was growing and the Iceland Meteorological Office suggested at that time that possibly magma intruded in the crust at shallow depth (3 to 9 km). The first eruption occurred on 19.03.2021, followed by many others in the foolwing years. The GFZ started a seismological Hazard and Risk Team (HART), as soon as February 2020 in cooperation with IMO, ISOR and the University of Iceland. The interrogator was located in Grindavik and was connected to a standard telecom cable. The full data dataset of this 5J network comprise 250 Tb of raw data. The standard infrastructure is not designed for such large data set. Therefore, we implement here several datasets, corresponding to several processing and associated publications. Specific full data set is available upon request to the authors. In Flovenz et al., 2022, the data subset comprise a selection of wave-forms recorded along an optical fibre of 21 km length. The subset consists of 40 channels at 100 Hz (spatially stacked 9x). The whole time period from January until August 2020 is covered, with a total size of 496 GB. The data is MiniSEED at 4096 bytes record length with STEIM2. In Maass et al., 2024, the data subset consists of two sections of contiguous channels (1701-2000 and 3921-4218, spatial sampling 4 meters) of dynamic strain rate down sampled at 5 Hz. The whole time period from January until August 2020 is covered, with a total size of 340 GB. The data is MiniSEED at 4096 bytes record length with STEIM2.

Sarez Pamir aftershock seismic network

The Sarez Pamir aftershock seismic network was installed two months after the 7 December 2015, Mw7.2 Sarez Pamir earthquake in the eastern Pamir highland of Tajikistan. In the first recording period until September 2016, the stations were distributed along the Sarez-Karakul fault system. In September 2016 part of the stations were moved into the southern Pamir. In total the network consisted of eight stations on 13 sites, equipped with broad band, 3-component seismometers of type Trillium Compact. The data were recorded using Earth Data recorders (EDR), recording was continuous at a sample rate of 100Hz.The principal aim of the network was to record the aftershock sequence of the Sarez earthquake and to augment the coeval East Pamir China seismic network and the earlier TIPAGE and TIPTIMON seismic networks. Waveform data are available from the GEOFON data centre, under network code 9H.

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