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  • 1
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    Project GAKKELDEEP: DEPAS ocean-bottom seismometer operations at the Gakkel Ridge in 2018-2019 (2022)
    PANGAEA
    Details
    Publication Date: 2024-04-20
    Description: 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.
    Keywords: 8F_GKD01; 8F_GKD02; 8F_GKD03; 8F_GKD04; Binary Object; Clock skew; Code; Comment; Cruise/expedition; Date/time end; Date/time start; DEPAS; ELEVATION; Event label; gakkel ridge; Gakkel Ridge, Arctic Ocean; Hydrophone, serial number; Hydrophone gain; Hydrophone polarity; Hydrophone type; LATITUDE; LONGITUDE; OBS; Ocean bottom seismometer; ocean-bottom seismometer; Optional event label; Passive seismology; Principal investigator; Project; PS115/2_4-1, PS122/1_2-30; PS115/2_5-1, PS122/1_2-22; PS115/2_6-1, PS122/1_2-23; PS115/2_7-1, PS122/1_2-24; Recorder, serial number; Recorder type; Sampling rate; Seismometer, serial number; Seismometer gain; Seismometer type; Station label
    Type: Dataset
    Format: text/tab-separated-values, 100 data points
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    DATA PANGAEA
  • 2
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    Wide‐Angle Seismic Imaging of Two Modes of Crustal Accretion in Mature Atlantic Ocean Crust (2020)
    American Geophysical Union
    Details
    Publication Date: 2020-06-01
    Print ISSN: 2169-9313
    Electronic ISSN: 2169-9356
    Topics: Geosciences , Physics
    Published by American Geophysical Union
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    PAPER CURRENT
  • 3
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    IMAGE (Integrated Methods for Advanced Geothermal Exploration) (2020)
    GFZ Data Services
    Details
    Publication Date: 2024-02-23
    Description: Abstract
    Description: IMAGE is a two year seismological experiment realized at the Reykjanes Peninsula by Philippe Jousset (GFZ Potsdam) and Gylfi P. Hersir (ISOR Iceland). Reykjanes Peninsula is located at the southwestern tip of Iceland, at the emergent part of the Mid-oceanic Ridge. This area has a high seismicity and is exploited for its high geothermal potential. The deployment is performed to carry out a local seismological study with techniques such as seismic tomography (earthquake based, e.g. Jousset et al., 2016, and ambient noise e.g., Martins et al., 2020). The aim of the seismic experiment is to monitor the seismic activity associated with the rift processes (Blank et al., 2020) and/or the induced seismicity. The network comprised 30 onland stations (GIPP) and 21 Ocean Bottom Seismometers (Lobsters, DEPAS). Onland stations were deployed from April 2014 until August 2015 and comprise 20 broadband seismic stations (Nanometrics Trillium Compact 120 s), 10 short-period sensors (Mark sensors 1 Hz) and data loggers (DATA-CUBE) with acquisition frequencies of 200 Hz. Sensors were buried 30-40 cm deep in the ground in containers. Data gaps are minimal, and occurred every 3 months when the batteries were exchanged and data downloaded from the DATA-CUBEs. OBS were deployed in August 2014 and recorded for about a year. From this dataset, a catalogue of about 2000 earthquakes could be extracted. Waveform data are available from the GEOFON data centre, under network code 4L.
    Keywords: Broadband seismic waveforms ; Seismic monitoring ; temporary local seismic network ; Monitoring system ; EARTH SCIENCE 〉 SOLID EARTH 〉 TECTONICS 〉 VOLCANIC ACTIVITY ; In Situ/Laboratory Instruments 〉 Magnetic/Motion Sensors 〉 Seismometers ; In Situ Land-based Platforms 〉 GEOPHYSICAL STATIONS/NETWORKS
    Type: Dataset , Seismic Network
    Format: ~3.2T
    Format: .mseed
    Format: XML
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    DATA GFZ
  • 4
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    GAKKELDEEP: DEPAS ocean-bottom seismometer operations at the Gakkel Ridge in 2018-2019 (2022)
    GFZ Data Services
    Details
    Publication Date: 2024-04-11
    Description: Abstract
    Description: “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, under network code 8F and are embargoed until June 2025.
    Keywords: In Situ/Laboratory Instruments 〉 Magnetic/Motion Sensors 〉 Seismometers ; In Situ Land-based Platforms 〉 GEOPHYSICAL STATIONS/NETWORKS ; OBS ; DEPAS ; Passive seismic ; Local network ; Temporary ; Velocity ; Hydrophones ; Seismometers ; MiniSEED
    Type: Dataset , Seismic Network
    Format: ~300G
    Format: .mseed
    Format: XML
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    DATA GFZ
  • 5
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    DEPAS – Deutscher Geräte-Pool für Amphibische Seismologie (2018)
    In:  EPIC344. Sitzung der AG Seismologie, Berggießhübel / Pirna, 2018-09-25-2018-09-27
    Details
    Publication Date: 2018-12-14
    Description: Der "Deutsche Geräte-Pool für amphibische Seismologie (DEPAS)" ist ein im Jahre 2005 gegründeter Pool breitbandiger Seismometer für Langzeiteinsätze an Land und auf dem Meeresboden. Er besteht zur Zeit aus 95 Landstationen, welche vom Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum (GFZ) betrieben werden, sowie aus 80 Ozeanboden-Seismometern (OBS), welche technisch und organisatorisch vom Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven (AWI)betreut werden. In diesem Beitrag wird der marine Teil des DEPAS-Pools vorgestellt, die Ozeanboden-Seismometer (OBS). Es werden unter anderem die Geräte-Technik und das Antragsverfahren erläutert. In den kommenden Jahren sollen die OBS durch den Austausch von Seismometern und Datenloggern technisch auf den neuesten Stand gebracht werden. Das Eigenrauschen der Seismometer bei langen Perioden und der Stromverbrauch des Gesamtsystems können damit erheblich reduziert werden. Eine aktuelle Eigenentwicklung befasst sich mit einer speziellen technischen Erweiterung der OBS für Einsätze in eisbedeckten Regionen.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 6
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    The German Instrument Pool for Amphibian Seismology (DEPAS) (2017)
    In:  EPIC32017 European OBS technical workshop, Paris, France, 2017-11-06-2017-11-07
    Details
    Publication Date: 2017-11-11
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 7
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    TRISTAN: Electromagnetic, gravimetric and seismic measurements to investigate the Tristan da Cunha hot spot and its role in the opening of the South-Atlantic - Cruise No. MSM20/2 - January 17 - February 15, 2012 - Walvis Bay (Namibia) - Recife (Brazil) (2015)
    DFG-Senatskommission für Ozeanographie
    In:  EPIC3MARIA S. MERIAN-Berichte, DFG-Senatskommission für Ozeanographie, MSM20/, 52 p.
    Details
    Publication Date: 2016-12-11
    Description: According to classical plume theory, the Tristan da Cunha hotspot is thought to have played a major role in the rifting of the South Atlantic margins and the creation of the aseismic Walvis Ridge by impinging at the base of the continental lithosphere shortly before or during the breakup of the South Atlantic margins. But Tristan da Cunha is enigmatic, as it cannot be clearly identified as a hot-spot but classifies also highly as a more shallow type of anomaly that may actually have been caused by the opening of the South Atlantic. The equivocal character of Tristan is largely due to lack of geophysical data in this region. To understand the tectonic processes of the opening of the South Atlantic, the formation of the Walvis ridge and to understand whether Tristan da Cunha is the cause or the consequence of rifting, it is of central importance to characterize the region around Tristan da Cunha in a more coherent way. Within this research cruise we deployed 26 ocean bottom electromagnetic stations (OEBM) and 24 ocean bottom seismometer (OBS) for a long term acquisition (1 year) of magnetotelluric and seismological data, acquired bathymetry and gravity data and performed geological sampling on Tristan da Cunha. The data will be interpreted in the context of geochemical data and tectonic models developed within the SPP1375 South Atlantic Margin Processes and Links with onshore Evolution (SAMPLE).
    Repository Name: EPIC Alfred Wegener Institut
    Type: Miscellaneous , notRev
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  • 8
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    MAX-DOAS measurements of BrO during the Antarctic Polarstern cruise in September 2006 (2006)
    In:  EPIC3Third International DOAS Workshop, 20-22 March, Bremen, Germany
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Format: application/pdf
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  • 9
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    Ambient seismic noise under the sea-ice of the Arctic Ocean: First results from a pilot experiment with Ocean Bottom Seismometers at eastern Gakkel Ridge (2021)
    In:  EPIC337th General Assembly of the European Seismological Commission, Corfu, Greece, 2021-09-19-2021-09-24
    Details
    Publication Date: 2021-11-11
    Description: Seismic monitoring of the cryosphere is mostly done with land seismometers on the surface of ice masses. Seismic monitoring beneath sea ice at the bottom of ice-covered oceans has hardly been attempted, because ocean bottom seismometers (OBS) are difficult to recover in perennial sea ice. As a result, for example the tectonic activity of the Arctic mid-ocean ridge system is poorly known. Recently, ambient seismic noise in long-term seismic records proved a useful tool to monitor the state of the sea ice cover. From September 2018 - September 2019, we deployed a trial network of 4 broadband OBS in Arctic sea ice. OBS were positioned at distances of 10 km at a water depth of 4 km on eastern Gakkel Ridge. Station noise levels from power spectral density analysis are considerably lower for sub-ice stations than for OBS in the Greenland Sea and are comparable to those of Arctic land stations. The network was designed to record local earthquakes along Gakkel Ridge, but it also yielded valuable data on the sub-ice ambient seismic noise in the Arctic Ocean. Spectrograms covering the entire deployment reveal pronounced seasonality in different frequency bands: Above 5 Hz, noise levels increase when sea ice cover is present. In addition, anthropogenic noise is prominently seen. The secondary microseismic noise peak has two clearly separable components with opposite seasonal evolution. Microseisms at 3-10 s periods relate to swell events outside the Arctic Ocean with a higher incidence of such events during winter time. In contrast, secondary microseisms originating in the Arctic Ocean peak in September during the annual sea ice minimum. Their periods increase from 0.5 s to 5 s as the fetch area for wave evolution increases from June to September.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 10
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    Seasonal variations in Arctic Ocean wave action and sea ice conditions recorded by deep-water broadband ocean bottom seismometers (2023)
    In:  EPIC3
    Details
    Publication Date: 2024-01-22
    Description: Studies of ambient seismic noise have proved a powerful tool to monitor the sea state in oceans, track large storms or even to conclude on the state of the sea ice covering the polar oceans. However, most studies of ambient noise use coastal seismic stations far from the source areas of seismic noise. Seasonal records of ambient seismic noise from the bottom of the polar oceans do not yet exist. In a pilot experiment from September 2018 to September 2019, we deployed four broadband ocean bottom seismometers at eastern Gakkel Ridge, Arctic Ocean, at water depths of about 4000 m underneath perennial sea ice. Only in August and September, the marginal ice zone of the Laptev Sea extended to the OBS position. Spectrograms show the seasonal variations of the ambient seismic noise. Long-period double-frequency microseisms are slightly stronger in winter time. Their source is outside the Arctic Ocean. Short-period double-frequency microseisms are seasonally modulated and appear when the Laptev Shelf area becomes ice-free, suggesting that deep water conditions are not necessary to produce mid-ocean microseism. The longest periods of this noise band increase as the fetch area for swell generation increases. At high frequencies (6-50Hz), considerable noise is present, mostly as short, distinct noise bands in winter time. We associate these signals to noise generated by the sea ice. To analyze the seasonality of the noise sources, we extracted the spectral power in various frequency bands for the entire year and compared it with variations of the significant wave height from Wave Watch III hindcast models and of ice concentration and drift from satellite data. This comparison revealed that sea ice-related noise decays suddenly in late May while sea ice concentration is still 100%, suggesting that the physical properties of the sea ice change at this time prior to break-up. Likewise, sea ice only gradually develops its noise-generating capabilities after the freezing period, when compression of ice floes contributes to their thickening. During autumn, several swell events cause large-amplitude short-period double-frequency microseisms and simultaneously high-frequency noise although ice-noise is otherwise not present in this season. Ice concentration decreases following the swell events, showing the impact of swell on the state of the sea ice during the freezing season.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
    Format: application/vnd.openxmlformats-officedocument.wordprocessingml.document
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