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This ocean-bottom seismometer deployment is part of an interdisciplinary project examining the Aurora hydrothermal vent field in an attempt to understand its fluid circulation. A total of 8 ocean bottom seismometers modified for the operation in sea ice covered oceans was deployed around Aurora vent field at the intersection of Gakkel Ridge and Lena Trough in the Fram Strait. The aim of the experiment was to monitor seismicity related to the hydrothermal circulation system and to reveal potentially heat reservoirs devoid of seismicity. The network consisted of 8 DEPAS Lobster type broadband OBS. Instruments were free-fall deployed and spaced by about 5-8 km. Their position at the seafloor is known to within few meters from ultrashort baseline positioning system Posidonia. The OBS recorded continuously at 100 Hz for up to 12 months between end of July 2022 and mid July 2023. One instrument (AUR02) had an unreliable seismometer records due to levelling problems. Skew values were obtained for all stations and ranged between -18 s and 12.3 s. Clock drift in this experiment was partially nonlinear. After the skew correction, a nonlinear time drift for stations AUR02, AUR04, AUR06, AUR08 was determined using noise cross-correlation. A best-fit correction was obtained by using skew-corrected station AUR01 as reference station for stations AUR04 and AUR08, while skew-corrected station AUR03 served as reference for stations AUR02 and AUR06. Station specific phase residuals obtained from a manually picked catalog of 492 events were used to further validate the clock drift corrections. For AUR04 a nonlinear phase residual drift was observed and, subsequently, the applied drift polynomial was manually adjusted to minimize resulting residuals. Waveform data are available from the GEOFON data centre under network code 4V.
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.
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.
A network of 210 continuously running, digital seismic stations equipped with short-period sensors (200 stations) and broadband sensors (10 stations) was deployed in an area of ~8 x ~6 km in the Irish Midlands (north of Collinstown) for a time period of ~6 weeks. The network was part of the EU project VECTOR (https://vectorproject.eu) aiming to investigate – among others – possible solutions for least invasive forms of exploration for mineral resources. In this context the collected data was mainly used to derive a 3D model of the subsurface (seismic shear wave velocity) using ambient noise tomography (down to ~1.5km depth). We thank all field crews for their excellent work rendered to the project. Waveform data is available from the GEOFON data centre, under network code 7W.
“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.
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.
The Eifel Large-N Seismic Network is a concentric network of about 80km aperture around the Laacher See. Instrumentation consists of broad band seismometers, short period instruments (1Hz eigenfrequency) and 4.5Hz geophones. While the broadband and short period stations cover the area rather homogeneously for about 12 month, the geophone stations were moved after 6 month from a layout focussed on the closer vicinity of the Laacher See onto a line crossing the network from south-west to north-east with a dense station spacing. The goal of the experiment is the structural investigation of the feeding system of the East Eifel and a detailed study of the tectonic and volcanic seismic activity in this area. Waveform data is available from the GEOFON data centre, under network code 6E.
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.
“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.
Irpinia seismic Array is part of the DEnse mulTi-paramEtriC observations and 4D high resoluTion imaging (DETECT) project focused on the acquisition of a unique multiparametric dataset and fosters collaboration among various institutions. The University of Naples Federico II (UniNa) and the German Research Centre for Geosciences (GFZ) are leading this effort carried out in collaboration with various local institutions and supported by the local municipalities. The DETECT project aims at exploiting very dense seismic networks deployed across a segmented fault system (Irpinia and Pergola-Melandro) to foster the development of scientific integrated methodologies for monitoring and imaging the fault behavior during the inter-seismic phase. The Irpinia seismic Array consists of a dense constellation of seismic antennas using more than 200 seismic stations deployed for one year. Each seismic antenna, with maximum aperture of ~2 km, uses one broad-band sensor, one short period sensor with 1 Hz and 8 with 4.5 Hz natural frequency. The antennas are deployed above and near the fault segments that generated during the last centuries many strong earthquakes in the southern Apennines. Waveform data are available from the GEOFON data centre, under network code ZK.
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