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  • 1
    Electronic Resource
    Electronic Resource
    Gas flux to the atmosphere from mud volcanoes in eastern Romania (2004)
    Oxford, UK : Blackwell Science Ltd
    Terra nova 16 (2004), S. 0 
    Details
    ISSN: 1365-3121
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Gas flux measurements have for the first time been taken from vents and soil of eastern Romania mud volcanoes, the largest geological structures in Europe releasing methane into the atmosphere. In the quiescent phase, the methane emission from single vents is up to 28 t yr−1. Diffuse soil microseepage is of the order of 102−105 mg m−2 day−1. A total output of at least 1200 tonnes of CH4 per year can be conservatively estimated over the area investigated alone (∼ 2.3 km2). Helium fluxes are up to five orders of magnitude higher than the average flux in a stable continental area, pointing to a close link between mud volcanoes and crustal degassing through faults crossing the deep hydrocarbon reservoirs. These data represent a key contribution towards refining global CH4-emission estimates, which indicate mud volcanoes as a significant and unavoidable source of greenhouse gases for the atmosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3121.2004.00542.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Laboratory simulation of geogas microbubble flow (1996)
    Springer
    Environmental geology 27 (1996), S. 226-232 
    Details
    ISSN: 1432-0495
    Keywords: Key words: Geogas ; Microbubbles ; Radionuclide transport ; Gas advection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Preliminary laboratory tests provided first data on the behavior of gas microbubbles through porous media in the framework of the geogas theory. Under experimented conditions with laboratory equipment arranged for pressure controlled gas-tracer injection and sampling, gas microbubbles moved up to ten times faster than single-phase flow in dry media under the same injection pressure. Microbubbles were determined to be very sensitive to changes in injection pressure and their terminal velocity seems to be described with good approximation by the Stokes formula. The capability of microbubbles to pick up and transport upward for short distances solid ultra-small particles (metallic and radionuclide compounds) has been proved. Results are consistent with a time-dependent process linked to the transport properties of microbubbles (e.g. flotation), such as that reported by some authors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002540050055
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Laboratory simulation of geogas microbubble flow (1996)
    Springer
    Environmental geology 27 (1996), S. 226-232 
    Details
    ISSN: 1432-0495
    Keywords: Geogas ; Microbubbles ; Radionuclide transport ; Gas advection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Preliminary laboratory tests provided first data on the behavior of gas microbubbles through porous media in the framework of the geogas theory. Under experimented conditions with laboratory equipment arranged for pressure controlled gas-tracer injection and sampling, gas microbubbles moved up to ten times faster than singlephase flow in dry media under the same injection pressure. Microbubbles were determined to be very sensitive to changes in injection pressure and their terminal velocity seems to be described with good approximation by the Stokes formula. The capability of microbubbles to pick up and transport upward for short distances solid ultra-small particles (metallic and radionuclide compounds) has been proved. Results are consistent with a time-dependent process linked to the transport properties of microbubbles (e.g., flotation), such as that reported by some authors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00770436
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Evidence for radon transport by carrier gas through faulted clays in Italy (1995)
    Springer
    Journal of radioanalytical and nuclear chemistry 193 (1995), S. 291-300 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Extensive soil-gas surveys in sedimentary basins in Italy were performed to study the potential of some naturally occurring gases as indicators for concealed fracture zones, hydrocarbon and geothermal fluids. One conclusive result is a positive correlation between anomalously high values of radon and carbon dioxide in the soil-air over faults. The correlation coefficient for 1173 gas samples is 0.41. Statistically derived contourlines of Rn and CO2 anomalies show similar locations, shapes and directions. Fairly good Rn−CO2 coupling evidence appears even on a point-to-point analysis. Furthermore, it was recognized that the highest Rn values are in contrast to the low Ra content of the underlying clayey rocks and that conventional Rn transportation mechanisms seem to be inadequate for the clay sequences. All these facts strongly suggest that Rn is transported from the subsoil, through fault-linked pathways, by carrier gases of which CO2 could be one of the major components. The theory of geogas microbubbles is a possible explanation of the observed results. The carrier effect of ascending microbubbles can explain both the origin of soil-gas Rn anomaly and the Rn−CO2 coupling phenomenon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02039886
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  • 5
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    Gas and seismicity within the Istanbul seismic gap (2018)
    Nature Research
    In:  Scientific Reports, 8 (Article number 6819).
    Details
    Publication Date: 2021-02-08
    Description: Understanding micro-seismicity is a critical question for earthquake hazard assessment. Since the devastating earthquakes of Izmit and Duzce in 1999, the seismicity along the submerged section of North Anatolian Fault within the Sea of Marmara (comprising the “Istanbul seismic gap”) has been extensively studied in order to infer its mechanical behaviour (creeping vs locked). So far, the seismicity has been interpreted only in terms of being tectonic-driven, although the Main Marmara Fault (MMF) is known to strike across multiple hydrocarbon gas sources. Here, we show that a large number of the aftershocks that followed the M 5.1 earthquake of July, 25th 2011 in the western Sea of Marmara, occurred within a zone of gas overpressuring in the 1.5–5 km depth range, from where pressurized gas is expected to migrate along the MMF, up to the surface sediment layers. Hence, gas-related processes should also be considered for a complete interpretation of the micro-seismicity (~M 〈 3) within the Istanbul offshore domain.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1038/s41598-018-23536-7
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Imaging shallow gas migration pathways in a mud‐volcano province using an autonomous underwater vehicle (Malta Plateau, Mediterranean Sea) (2018)
    EAGE
    In:  Near Surface Geophysics, 16 (6). pp. 681-699.
    Details
    Publication Date: 2019-01-02
    Description: Data acquired by an autonomous underwater vehicle (AUV) towing a source (1600–3500 Hz) and a horizontal array of hydrophones have been analysed to image discrete, isolated or even a small cluster of scatterers within the sediment, to determine shallow migration paths of hydrocarbons in a mud volcano system of the Malta Plateau. An algorithm based on a semblance function was applied to the acoustic data to highlight scatterers rather than interface reflections. The resulting scatterer map, obtained along the AUV track, generated a pseudo‐three‐dimensional coverage of the study area, with a horizontal and vertical resolution of roughly 3–5 m and 5–10 m, respectively. This map was combined with high‐resolution bathymetric and backscattering seafloor maps obtained from previous explorations. This integrated dataset provides new evidence for the role of fault zones as a preferential path for gas/fluid migration and reveals the intermittent activity of seeping gas. The data show, in particular, that gas bubble slugs, i.e. discontinuous gas columns, rise through Plio‐Quaternary sediments along a complex system of conduits terminating at the surface into quiescent mud volcanoes. The gas flux is facilitated by the regional stress field that results in dilatant conditions on the mapped fault zones.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/nsg.12017
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  • 7
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    Monitoring of gas and seismic energy release by multiparametric benthic observatory along the North Anatolian Fault in the Sea of Marmara (NW Turkey) (2014)
    Wiley
    In:  Geophysical Journal International, 196 (2). pp. 850-866.
    Details
    Publication Date: 2015-07-24
    Description: Episodic gas seepage occurs at the seafloor in the Gulf of Izmit (Sea of Marmara, NW Turkey) along the submerged segment of the North Anatolian Fault (NAF), which ruptured during the 1999 Mw7.4 Izmit earthquake, and caused tectonic loading of the fault segment in front of the Istanbul metropolitan area. In order to study gas seepage and seismic energy release along the NAF, a multiparametric benthic observatory (SN-4) was deployed in the gulf at the western end of the 1999 Izmit earthquake rupture, and operated for about 1 yr at 166 m water depth. The SN-4 payload included a three-component broad-band seismometer, as well as gas and oceanographic sensors. We analysed data collected continuously for 161 d in the first part of the experiment, from 2009 October to 2010 March. The main objective of our work was to verify whether tectonic deformation along the NAF could trigger methane seepage. For this reason, we considered only local seismicity, that is, within 100 km from the station. No significant (ML ≥ 3.6) local earthquakes occurred during this period; on the other hand, the seismometer recorded high-frequency SDEs (short duration events), which are not related to seismicity but to abrupt increases of dissolved methane concentration in the sea water that we called MPEs (methane peak events). Acquisition of current velocity, dissolved oxygen, turbidity, temperature and salinity, allowed us to analyse the local oceanographic setting during each event, and correlate SDEs to episodic gas discharges from the seabed. We noted that MPEs are the result of such gas releases, but are detected only under favourable oceanographic conditions. This stresses the importance of collecting long-term multiparametric time-series to address complex phenomena such as gas and seismic energy release at the seafloor. Results from the SN-4 experiment in the Sea of Marmara suggest that neither low-magnitude local seismicity, nor regional events affect intensity and frequency of gas flows from the seafloor.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1093/gji/ggt436
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  • 8
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    Cold seeps, active faults and the earthquake cycle along the North Anatolian Fault system in the Sea of Marmara (NW Turkey) (2012)
    Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS
    In:  Bolletino di Geofisica Teorica ed Applicata, 53 (4). pp. 371-384.
    Details
    Publication Date: 2014-03-11
    Description: After the 1999 I . zmit earthquake (Mw7.4), along the North-Anatolian Fault (NAF), an increase in gas emissions from the seafloor of the Sea of Marmara was observed. Using a multidisciplinary approach, that includes a combined analysis of high-resolution marine geophysical and gas-geochemical data, we determined the character of gas/fluid emissions and their spatial relationship with tectonic structures in the Darıca Basin (Gulf of Izmit), close to the western termination of the 1999 earthquake surface rupture. Data collected during several oceanographic expeditions allowed us to investigate the fine structure of active fault branches, as well as the geochemical signature of the cold seeps. We observed that gas emissions at the seafloor of the Darıca Basin are mostly constituted by biogenic CH4, and are aligned along strike-slip and transtensional fault segments. Although maximum CH4 concentrations were measured in correspondence of transtensional strands, we suggest that the biogenic CH4 emissions found along strike-slip segments, showing a relatively low gas background noise and a potential to increase during seismic events, are more suitable to study relationships between gas expulsion and the earthquake cycle.
    Type: Article , PeerReviewed
    Format: text
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  • 9
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    Gas seepage and seismogenic structures along the North Anatolian Fault in the eastern Sea of Marmara (2012)
    AGU (American Geophysical Union)
    In:  Geochemistry, Geophysics, Geosystems, 13 (10). n/a-n/a.
    Details
    Publication Date: 2014-03-11
    Description: We carried out a combined geophysical and gas-geochemical survey on an active fault strand along the North Anatolian Fault (NAF) system in the Gulf of İzmit (eastern Sea of Marmara), providing for the first time in this area data on the distribution of methane (CH4) and other gases dissolved in the bottom seawater, as well as the CH4isotopic composition. Based on high-resolution morphobathymetric data and chirp-sonar seismic reflection profiles we selected three areas with different tectonic features associated to the NAF system, where we performed visual and instrumental seafloor inspections, including in situ measurements of dissolved CH4, and sampling of the bottom water. Starting from background values of 2–10 nM, methane concentration in the bottom seawater increases abruptly up to 20 nM over the main NAF trace. CH4 concentration peaks up to ∼120 nM were detected above mounds related probably to gas and fluids expulsion. Methane is microbial (δ13CCH4: −67.3 and −76‰ versus VPDB), and was found mainly associated with pre-Holocene deposits topped by a 10–20 m thick draping of marine mud. The correlation between tectonic structures and gas-seepages at the seafloor suggests that the NAF in the Gulf of İzmit could represent a key site for long-term combined monitoring of fluid exhalations and seismicity to assess their potential as earthquake precursors.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2012GC004190
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  • 10
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    Investigating hypoxia in aquatic environments: diverse approaches to addressing a complex phenomenon (2014)
    Copernicus Publications (EGU)
    In:  Biogeosciences (BG), 11 . pp. 1215-1259.
    Details
    Publication Date: 2019-09-23
    Description: In this paper we provide an overview of new knowledge on oxygen depletion (hypoxia) and related phenomena in aquatic systems resulting from the EU-FP7 project HYPOX ("In situ monitoring of oxygen depletion in hypoxic ecosystems of coastal and open seas, and landlocked water bodies", www.hypox.net). In view of the anticipated oxygen loss in aquatic systems due to eutrophication and climate change, HYPOX was set up to improve capacities to monitor hypoxia as well as to understand its causes and consequences. Temporal dynamics and spatial patterns of hypoxia were analyzed in field studies in various aquatic environments, including the Baltic Sea, the Black Sea, Scottish and Scandinavian fjords, Ionian Sea lagoons and embayments, and Swiss lakes. Examples of episodic and rapid (hours) occurrences of hypoxia, as well as seasonal changes in bottom-water oxygenation in stratified systems, are discussed. Geologically driven hypoxia caused by gas seepage is demonstrated. Using novel technologies, temporal and spatial patterns of water-column oxygenation, from basin-scale seasonal patterns to meter-scale sub-micromolar oxygen distributions, were resolved. Existing multidecadal monitoring data were used to demonstrate the imprint of climate change and eutrophication on long-term oxygen distributions. Organic and inorganic proxies were used to extend investigations on past oxygen conditions to centennial and even longer timescales that cannot be resolved by monitoring. The effects of hypoxia on faunal communities and biogeochemical processes were also addressed in the project. An investigation of benthic fauna is presented as an example of hypoxia-devastated benthic communities that slowly recover upon a reduction in eutrophication in a system where naturally occurring hypoxia overlaps with anthropogenic hypoxia. Biogeochemical investigations reveal that oxygen intrusions have a strong effect on the microbially mediated redox cycling of elements. Observations and modeling studies of the sediments demonstrate the effect of seasonally changing oxygen conditions on benthic mineralization pathways and fluxes. Data quality and access are crucial in hypoxia research. Technical issues are therefore also addressed, including the availability of suitable sensor technology to resolve the gradual changes in bottom-water oxygen in marine systems that can be expected as a result of climate change. Using cabled observatories as examples, we show how the benefit of continuous oxygen monitoring can be maximized by adopting proper quality control. Finally, we discuss strategies for state-of-the-art data archiving and dissemination in compliance with global standards, and how ocean observations can contribute to global earth observation attempts.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.5194/bg-11-1215-2014
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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