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Understanding physical processes prior and during eruptions remains challenging, due to uncertainties about subsurface structures and undetected processes within the volcano. Here, the authors use a dedicated fibre-optic cable to obtain strain data and identify volcanic events and image hidden near-surface volcanic structural features at Etna volcano, Italy. In the paper Jousset et al. (2022), we detect and characterize strain signals associated with explosions, and we find evidences for non-linear grain interactions in a scoria layer of spatially variable thickness. We also demonstrate that wavefield separation allows us to incrementally investigate the ground response to various excitation mechanisms, and we identify very small volcanic events, which we relate to fluid migration and degassing. We recorded seismic signals from natural and man-made sources with 2-m spacing along a 1.5-km-long fibre-optic cable layout near the summit of actives craters of Etna volcano, Italy. Those results provide the basis for improved volcano monitoring and hazard assessment using DAS. This data publication contains the full data set used for the analysis. This data set comprises strain-rate data from 1 iDAS interrogator (~750 traces), velocity data from 15 geophones and 4 broadband seismometers, and infrasonic pressure data from infrasound sensors. For further explanation of the data and related processing steps, please refer to Jousset et al. (2022). Waveform data are available from the GEOFON data centre, under network code 9N.
A temporary installation has been realized in the Netherlands, in the region of the Groningen gas field. The objective of this installation is to test the usage of a conventional array layout for detection of microseismicity. The region of the Groningen gas field is an excellent test ground, since the operating company NAM (Nederlandse Aardolie Maatschappij) installed a multitude of shallow borehole stations from 2014 to 2017, of which 65 – in addition to the already existing shallow borehole stations installed by KNMI (Koninklijk Nederlands Meteorologisch Instituut) – were already online during the time of measurement, thus ensuring an earthquake catalogue that is complete down to low magnitudes during the time of array installation. The site for the installation was decided together with local parties involved in the seismicity monitoring, i.e. KNMI and NAM, and was located close to the village of Wittewierum. Stations were installed from the 12th of July 2016 to the 29th of August 2016 (49 days). The array was composed of 9 stations. The array was constructed in three concentric rings of 75 m, 150 m and 225 m diameter including a central station, but the geometry had to be adapted to the local conditions. Each station consisted of a broadband sensor (Trillium 120 s), an acquisition system (CUBE datalogger), a battery, and a GPS antenna. The entire system was installed at ~1 m depth (apart from GPS and transmission antennas), requiring only the digging of shallow holes, one for the installation of a thin concrete plate and the sensor, another one for a box containing the remaining instrumentation. The array stations recorded continuously with little outages; only station WAR1 stopped recording on the 22nd of August and station WAR7 stopped recording from 20th to 22nd of August. Waveform data is available from the GEOFON data centre, under network code 1C, and is fully open.
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.
The TOMO-ETNA experiment was focused on the base of generation and acquisition of seismic signal (active and passive) at Mt. Etna volcano and surrounding area. The terrestrial campaign consists in the deployment of 80 short-period three-component seismic stations (June 15 to July24), 17 Broadband seismometers (June 15 to October 30) provided by Helmholtz Centre Potsdam (GFZ) German Research Centre for Geosciences using the German Geophysical Instrument Pool Potsdam (GIPP Gerätepool Geophysik), and the coordination with 133 permanent seismic station belonging to the “Istituto Nazionale di Geofisica e Vulcanologia” (INGV) of Italy. This temporary seismic network recorded active and passive seismic sources. Active seismic sources were generated by an array of air-guns mounted in the Spanish Oceanographic vessel “Sarmiento de Gamboa” with a power capacity of up to 5.200 cubic inches. In total more than 26.000 shots were fired and more than 450 local and regional earthquakes were recorded. Until July the Oceanographic Vessel “Sarmiento de Gamboa” and the hydrographic vessel “Galatea” were responsible for the offshore activities, that included deployment of OBSs, and several marine activities. The vessel “Aegaeo” performed additional seismic, magnetic and gravimetric experiments until the end of November 2014. This experiment was part of the “Task 5.3 - Mt. Etna structure” of the “EU MED-SUV Project” concerned with the investigation of Mt. Etna volcano (seismic tomography experiment - TOMO-ETNA) by means of passive and active refraction/reflection seismic methods. It focused on the investigation of Etna’s roots and surrounding areas by means of passive and active seismic methods. Therefore, this experiment included activities both on-land and offshore with the main objective to obtain a new high-resolution tomography in order to improve the 3D image of the crustal structures existing beneath the Etna volcano and the northeast Sicily (Peloritani - Nebrodi chain) up to the Aeolian Islands. Waveform data are open and available from the GEOFON data centre, under network code 1T.
“Gakkel Deep is a pilot project that installed a network of four broadband ocean bottom seismometers (OBS) near Gakkel Deep, the deepest depression in the Arctic Ocean, at the eastern end of the ultraslow spreading Gakkel Ridge. The area is covered year-round by sea ice. In order to enable a safe recovery of the OBS in a sea ice covered ocean, the OBS were modified to include a positioning system that allows to track the instruments at meter accuracy during descent and ascent and when stuck beneath ice floes. This pilot studied aimed at testing the recovery procedure of the OBS, checking the performance of the modified instrument design, getting an overview of ambient seismic noise at the bottom of the Arctic Ocean and at contributing to a better understanding of the origin of the Gakkel Deep depression with more than 3000 m of topography. The network is shaped as a rectangle with 8 km and 10 km side length and is centered at about 82°N 119.5°E at water depths between 3600 m and 4100 m. It is positioned slightly to the east of the present plate boundary in an area with volcanic structures. Instruments from the German Instrument Pool of Amphibian Seismology (DEPAS) were deployed during RV Polarstern cruise PS115/2 on September 15, 2018. Instrument recovery was completed during RV Polarstern cruise PS122/1 on September 27, 2019. The data set contains about 377 days of continuous records at 250 Hz sample rate. The station locations were determined with Ultra Short Baseline (USBL) ranging, the accuracy is approx. 10 m. The non-linear clock drift was determined by means of noise cross-correlations and applied to the data set. Waveform data are available from the GEOFON data centre.
To seismically monitor the GEOREAL hydraulic stimulation experiment, that took place during the period 6-15 November 2023, a station network was set up in the vicinity of the Kontinentale Tiefbohrung/ KTB deep crustal lab near Windischeschenbach, Germany. The network comprised both surface stations, shallow borehole (25-150 m deep) stations as well as a borehole chain at 2000 m depth in the main borehole, ca. 200m apart from the pilot borehole. First stations were installed in early 2022 and removed in mid-2024. A total of 600 m³ of water was injected into the 4 km deep pilot borehole (KTB-VB, 12° 7.16' E, 49° 48.98' N, 513.418 m above NN ). This volume was injected through a stuck packer in the cased borehole into the open borehole section a depth of 3.85-4 km. No induced seismicity was observed during the injection experiment. Waveform data is available from the GEOFON data centre, under network code 4R, and is fully open.
For broadband ocean bottom seismometer (OBS) data, external noise is typically more pronounced than on seismometers installed onshore. However, the sources of this external noise are only partly understood. In particular, the impact the instrument design (form-factor of the floatation, pressure vessel, hight-to-width ratio) has on the amplitude of external noise is not fully understood. As a developer of OBS systems, K.U.M. Kiel GmbH has deployed two different types of OBS systems side-by-side for a period of 77 days. Both instruments included the same seismic sensor, a Nanometrics Trillium Compact 120 OBS. Station LOBS was a K.U.M. LOBSTER-type instrument carrier (https://jlsrf.org/index.php/lsf/article/view/165) which is the main instrument type in the DEPAS pool “German instrument pool for amphibian seismology”(https://www.awi.de/en/science/geosciences/geophysics/methods-and-tools/ocean-bottom-seismometer/depas.html). Station NEUA was a more recently developed system of the K.U.M. NAMMU-Type instrument, that has a completely different design (https://www.kum-kiel.de/products/nammu.html), with a single flotation, a single pressure tube containing the seismometer, datalogger and batteries. The side-by-side deployment of the different instruments allows a direct comparison and the availability of the oceanographic and meteorological data from the nearby metocean station DARSS-SILL (https://www.io-warnemuende.de/marnet-darss-sill.html) allows a detailed investigations of the instrument-design-related noise sources at OBS stations. Waveform data is available from the GEOFON data centre, under network code 1Q.
“This ocean-bottom seismometer deployment is part of the SEAMSTRESS project examining tectonic stress effects on Arctic methane seepage. The project is led by PI Andreia Plaza-Faverola at the Centre for Arctic Gas Hydrates, University of Tromsö, Norway. A total of 10 ocean bottom seismometers (OBS) were deployed on Vestnesa Ridge, a sediment drift body just north Knipovich Ridge at its intersection with the Molloy Transform fault (cruise CAGE-20-5). The aim of the experiment was to look for stress release along faults that control seepage sites on Vestnesa Ridge. The network consisted of 8 Lobster type broadband OBS from the German Instrument Pool for Amphibian Seismology (DEPAS) and 2 3C geophones provided by the University of Tromsö. Instruments were free-fall deployed and spaced by about 10 km. They recorded continuously at 100 Hz for 11 months between August 2020 and July 2021.Short, intersecting refraction profiles were shot across all OBS stations, such that OBS positions at the seafloor could be determined within 10 m (cruise CAGE-21-3). Clock drift in this experiment was nonlinear and skew values were only obtained for 6 of the stations. Skew-corrected station VSN01 served as reference station to obtain the clock drift of all other stations using noise cross-correlation and subsequently correct also for the thus determined nonlinearity of time drift. Waveform data are available from the GEOFON data centre, under network code Y9.
A temporary seismic network was installed in Sri Lanka for a time period of 13 months. The stations were equipped with Earth Data EDR-210 digital recorders and Trillium 120 PA, Güralp C3E and Güralp CMG-3ESP broadband sensors. Main aim of the network is to shed light on the crustal and upper mantle structure beneath the island. Also local seismic activity is studied.
This ocean-bottom seismometer deployment is part of the LoCHnESs (Loki Castle Hydrothermal iN-situ Experiments and Surveys) project examining hydrothermal fluid circulation at Loki's Castle vent field. The project is led by PI Thibaut Barreyre at the Centre for Deep Sea Research, Department of Earth Science, University of Bergen, Norway. A total of 8 ocean bottom seismometers (OBS) were deployed near Loki's Castle vent field at the Mohns-Knipovich Ridge bend, Norwegian-Greenland Sea. The aim of the experiment was to monitor seismicity related to changes in the hydrothermal circulation system and to reveal interaction between an active detachment fault and the axial volcanic ridge hosting the vent site. The network consisted of 8 DEPAS Lobster type broadband OBS from the German Instrument Pool for Amphibian Seismology (DEPAS). Instruments were free-fall deployed and spaced by about 5-8 km. They recorded continuously at 100 Hz for 12 months between July 2019 and July 2020. Two instruments (LOK01 and LOK06) could only be deployed one month later and recorded at 250 Hz. OBS positions at the seafloor were determined by interpolation at 2/3 of the distance between the deployment and recovery position at the seafloor. Position accuracy is estimated to be about 100 m. Skew values were obtained for all stations and reached values of up to 24 s. Clock drift in this experiment was nonlinear. Skew-corrected station LOK02 served as reference station to obtain the clock drift of all other stations using noise cross-correlation and subsequently correct also for the thus determined nonlinearity of time drift. Waveform data are available from the GEOFON data centre, under network code 8M.
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