The NEARESTproject (Integrated observations from NEAR shore sourcES of Tsunamis: towards an early warning system) aimed at the identification and characterization of potential near-shore sources of tsunamis in the Gulf of Cadiz. This area is well known from the catastrophic earthquake and tsunami that destroyed Lisbon and several other places mainly along the EastAtlantic coast on November 1st, 1755. One of the project's work packages dealed with monitoring of recent seismic activity in the Gulf of Cadiz area. For this purpose 24 broadband ocean-bottom seismometers (OBS) from the German DEPAS instrument pool were deployed for 11 months in addition to the GEOSTAR multi-parameter deep-sea observatory and two temporary land stations in Portugal. The GEOSTAR observatory and the 24 OBS were deployed and recovered during two expeditions with RV Urania in 2007 and 2008. The OBSs consist of three‐component Guralp CMG‐40T‐OBS seismometers and HighTech HTI‐04‐PCA/ULF hydrophones. A wide range of signals was recorded, ncluding teleseismic, regional and local earthquakes, and low‐frequency (∼20 Hz) vocalization of fin whales. The GEOSTAR observatory was again deployed between 2009 and 2011. The Portuguese temporary land station PDRG was additionally recording during the NEAREST project. Originally, the position of recovery on deck was taken to calculate the mean coordinate of the OBS at depth from deployment and recovery coordinates. In most cases the difference in coordinates between deployment and recovery is very small (table 3 and 4 in Carrara et al., 2008). For two stations, the location at the seafloor could be measured by triangulation (Carrara et al., 2008). Due to experience of other experiments over the years, we finally suggest to use the deployment coordinates as the station coordinates for all stations that could not be tri-angulated. The clocks were synchronized with GPS time before the deployment and if possible again after the recovery. Unfortunately, most of the batteries were empty at the end of the recording period. That either made it impossible to realize the second synchronisation (skew time measurement) or in some case also caused erroneous synchronisations. Therefore, the internal clock drift was estimated by ambient noise analysis (Corela, 2014). The internal clock drifts were corrected using a linear interpolation method. Generally, the data quality is very good, especially for the intended study of local and regional earthquakes. Studies relying on wideband seismological recordings can also be carried out. The sensor package and noise conditions hamper the use for broadband and very broadband applications. Unfortunately, also not all channels operated properly, therefore hampering the use of multi-component methods for the relevant stations. We thank the captain E. Gentile, crew, G. Carrara, and all participants of the R/V URANIA expeditions in 2007 and 2008. We are grateful to all people and institutions involved in the NEAREST project. Waveform data is available from the GEOFON data centre, under network code 9H.
This is the first deployment of a teleseismic broadband array consisting of 12 three-component stations with an aperture of about 50 km in the deep ocean in about 5000 m water depth. The data can be compared with two other deployments on Madeira and in western Portugal mainland which had similar array layouts and recording time spans (network Y7). The broadband data enable furthermore analysis of the crust and upper mantle beneath the array near to the Gloria fault, a major transform fault in the North Atlantic. Recordings of numerous local and regional earthquakes make a precise location of active structures possible. Waveform data is available from the GEOFON data centre, under network code 3J.
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.
These data were produced in two lab assays. The first assay was conducted in the period from August 29 to September 10, during which filtration and respiration of 18 mussels transplanted and grown for ca. four months under thermal history levels of + 0 °C and + 4 °C (using Kiel Outdoor Benthocosms, KOBs) were recorded in six temporally replicated (independent) trials using the Fluorometer and Oximeter-equipped Flow-through Setup (FOFS; Vajedsamiei et al., 2021). In each trial, filtration and respiration of three different transplants, randomly selected from the incubated samples were recorded in response to a constant mild temperature condition (20.8 °C) followed by two 24 h thermal fluctuation cycles. In the second assay, we recorded filtration and respiration rates of six batches of 5 or 6 mussels recruited and grown under the same thermal history levels in KOBs (three batches from each thermal history level) in temporally replicated trials of the same FOFS treatment, as explained earlier.
BEAR ISLAND (The Dynamic Continental Margin Between the Mid-Atlantic-Ridge System (Mohns Ridge, Knipovich Ridge) and the Bear Island Region) is an interdisciplinary project exploring the stress conditions and sources, and the dynamics and deformation characteristics of the continental margin between the Mid-Atlantic Ridge and Bear Island from its top sedimentary cover to its imprint in the upper mantle. In this region the margin includes an extremely thick sedimentary wedge and steep slopes, with at least one major paleo-fracture zone cutting through the wedge. Recent studies in this area indicate very low seismic velocities in the lithosphere and the stress field undergoes an extensional-compressional transition. It is therefore of particular interest to understand the structural architecture, the stress and the dynamics of the whole region because of its natural hazard exposure and the processes involved in the formation of the margin and the opening of the North Atlantic. To achieve this, deep seismic sounding data, as well as records from temporary broadband installations, supplementary to data from existing seismic stations in the region were collected. A key element of the project was the operation of a long-term network of broadband ocean-bottom seismometers (OBS). Additionally, two new broadband seismometers and a small temporary seismic array with 13 sensors were operated. Active seismic refraction/reflection experiments were conducted along two profiles crossing the region and recorded with additional short period OBSs and land stations. Twelve broadband ocean-bottom seismometers (OBS) from the German Instrument Pool of Amphibian Seismology (DEPAS) were deployed as part of this network with RV Horyzont II in September 2007. They were distributed on the Barents shelf, the slope and the deep sea near the Mid-Atlantic Ridge. Nine instruments could be recovered in August 2008 with RV Horyzont II. One instrument was fished before, one was destroyed during recovery and one got lost. Seven stations recorded data for the full deployment period; two stations have no skew value. The time correction for these stations was estimated by noise cross-correlations. Based on previous experiments, the accuracy of the positions is estimated to 500 m. Waveform data is available from the GEOFON data centre, under network code 9C.
The WAVEOBS project was established with three primary goals; to get a better fundamental understanding of microseism sources in the north-east Atlantic near Ireland; to investigate the use of ocean generated microseisms as real time ocean wave height data; and to investigate their use as a climate proxy. Waveform data is available from the GEOFON data centre, under network code 4V, and is fully open.
BRAVOSEIS (Bransfield Volcano Seismology) is an interdisciplinary project exploring volcanism in the Bransfield back-arc basin, Antarctica. Partners from Spain (amongst others UGR, project leader), Germany (AWI, GFZ) and the US (CUNY, UW, WHOI) performed various geophysical onshore and offshore measurements in the Antarctis seasons 2017-2018, 2018-2019 and 2019-2020. A key element of the project was the operation of a large long-term amphibious network of broadband seismometer in the Bransfield Strait, on the adjoining South Shetland Islands, and on the Antarctic Peninsula. Nine broadband ocean-bottom seismometer (OBS) from the German Instrument Pool of Amphibian Seismology (DEPAS) were deployed as part of this network with RV Sarmiento de Gamboa in January 2019 (cruise SDG076). They were distributed along the entire basin, one station supplemented a dense array of short-period OBS around the Orca seamount. Eight instruments could be recovered in February 2020 with RV Hespérides (cruise HE0188), one OBS is still missing. All stations recorded data for the full deployment period. Unfortunately, the clock drift of all stations turned out to be non-linear, a skew measurement was possible for four stations only. The clock drift was corrected by means of noise cross-correlations. Based on previous experiments, the accuracy of the positions is estimated to 500 m. Waveform data is available from the GEOFON data centre, under network code ZX.
The aim of the project is to deploy 10 Broad Band Ocean Bottom Seismographs (OBSs) units across the shelf offshore Donegal and out into the Rockall Trough in order to study microseims. Compared to earthquakes, microseisms represent background seismic noise generated by ocean wave pressure fluctuations on the sea floor which generate low frequency seismic waves. This project is a collaboration between the Dublin Institute for Advanced Studies (DIAS) and the Helmholtz Center GFZ Potsdam (Germany) with instruments provided by the Alfred Wegener Institute (AWI in Germany). Waveform data is available from the GEOFON data centre, under network code 2V.
The goal of the UPFLOW project is to develop new high-resolution seismic imaging approaches along with new data collection, and to use them to constrain upward flow in unprecedented detail. We conducted a large off-shore experiment in the Azores-Madeira-Canary Islands region, which is a unique natural laboratory with multiple upwellings that are poorly understood in general. UPFLOW deployed and recovered 49 ocean bottom seismometers (OBSs) in a ~1,000×2,000 km2 area in the Azores-Madeira-Canary Islands region starting in July 2021 for ~13 months, with an average spacing of ~150-200 km. The seismic deployment and recovery involved institutions from five different countries: Portugal (IPMA, IDL, Univ. of Lisbon, ISEL), Ireland (DIAS), UK (UCL), Spain (ROA) and Germany (Potsdam University, GFZ, Geomar, AWI). 32 OBSs were rented from the DEPAS international pool of instruments maintained by the Alfred Wegener Institute (Bremerhaven), Germany, while other institutions borrowed additional instruments (7 from DIAS, 4 from IDL, 3 from ROA, 4 from GEOMAR). Most of the instruments have three-component wideband seismic sensors, but three different designs of OBS frames were used. Waveform data is available from the GEOFON data centre, under network code 8J, embargoed data may be accessible upon request. We want to acknowledge the exceptional support of the whole team of able seaman, steward, cooks, engineers, mechanicians, electricians and motorman assistants of the vessel RRV Mário Ruivo. With special Thanks to José Ângelo Gomes (Captain), Luís Ramos (Superintendent), Mafalda Carapuço Vessel’s manager (IPMA), Henrique Ferreira Land logistics (IPMA), Celine Ahmed and Jen Amery (Administrative support at UCL)
“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.
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