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  • 1
    Online Resource
    Online Resource
    Crustal structure of the Mid-Atlantic Ridge at 5° south : two contrasting spreading segments (2006)
    Details Availability
    Keywords: Hochschulschrift ; Mittelatlantischer Rücken ; Ozeanische Erdkruste
    Description / Table of Contents: The structure of the oceanic crust at the Mid-Atlantic Ridge at 5ʿ South is investigated using wide-angle seismic data. Here, two morphologically contrasting spreading segments are separated by a 70 km offset transform fault. Applying a first-arrival tomography and a joint refraction and reflection tomography the obtained models show strong lateral heterogeneity in both velocities and Moho depths. In the segment north of the 5ʿS fracture zone (FZ) the along-axis crustal thickness thins from 9 km at the segment center to 5-6 km at the segment ends. In contrast to the magmatically robust northern segment, spreading south of the 5ʿS FZ rather seems to be tectonically controlled. Here, an inside corner high has been split by a change in location of active seafloor spreading. Most parts of this segment are underlain by anomalously thin crust with the thinnest portions associated with the flanks of the inside corner high and a fossil second order ridge-axis discontinuity. The crust formed at the inside corner reveals throughoutly higher velocities than corresponding outside corner crust, which is consistent with models of asymmetric crustal accretion along a detachment fault.
    Type of Medium: Online Resource
    Pages: Online-Ressource (217 S.)
    URL: http://e-diss.uni-kiel.de/diss_1837/d1837.pdf
    URL: http://e-diss.uni-kiel.de/diss_1837/index.htm
    URL: http://d-nb.info/980891280/34
    URL: http://nbn-resolving.de/urn:nbn:de:gbv:8-diss_18377
    URN: urn:nbn:de:gbv:8-diss-18374
    DDC: 550
    Language: English
    Note: Kiel, Univ., Diss, 2006
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  • 2
    Online Resource
    Online Resource
    Along- and across-axis variations in crustal thickness and structure at the Mid-Atlantic Ridge at 5°S obtained from wide-angle seismic tomography : implications for ridge segmentation (2009)
    Associated volumes
    Details Availability
    In: Journal of geophysical research. B, Solid earth, Hoboken, NJ : Wiley, 1978, 114(2009), 2169-9356
    In: volume:114
    In: year:2009
    In: extent:20
    Description / Table of Contents: Two end-member styles of crustal accretion are observed at two adjacent spreading segments at the Mid-Atlantic Ridge at 5°S: focused accretion to the segment center with rapid crustal thinning toward the transform in the northern segment and crustal thickening toward the transform at an oceanic core complex in the southern segment. Our results were obtained by tomographic inversion of wide-angle seismic reflection and refraction data collected along three intersecting profiles. The segment north of the 5°S fracture zone is characterized by a well-developed median valley with a pronounced seafloor bulge in the segment center. A discrete portion of anomalously low velocities (-0.4 to -0.5 km/s relative to average off-axis structure) at depths of ~2.5 km beneath this bulge is possibly related to the presence of elevated temperatures and perhaps small portions of partial melt. This suggests that this segment is currently in a magmatically active period, which is confirmed by the observation of fresh lava flows and ongoing high-temperature hydrothermal activity at the seafloor. Close to the current spreading axis, the crust thins rapidly from 8.5 km beneath the segment center to less than 3 km beneath the transform fault which indicates that melt supply here is strongly focused to the segment center. The reduction in crustal thickness is almost exclusively accommodated by the thinning of velocity portions indicative of seismic layer 3. The transform fault is characterized by more uniform velocity gradients throughout the entire crustal section and very low upper mantle velocities of 7.2-7.3 km/s indicating that serpentinization could be as much as 25% at 3.5 km depth. In contrast, ~4.1 Ma old crust of the northern segment shows only minor thinning from the segment center toward the segment end. Here, the transform is characterized by a normal seismic layer 2/3 transition suggesting robust melt supply to the segment end at those times. In the adjacent southern segment, the crust thickens from ~2.5 km beneath the flank of an oceanic core complex to ~5.0 km at the segment boundary. The observed changes in crustal thickness show a significant temporal and lateral variability in melt supply and suggest a more complex crustal emplacement process than predicted by models of focused melt supply to the segment centers.
    Type of Medium: Online Resource
    Pages: 20 , graph. Darst
    ISSN: 2169-9356
    DOI: 10.1029/2008JB006103
    Language: English
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  • 3
    Online Resource
    Online Resource
    Crustal structure of the central Costa Rica subduction zone : implications for basal erosion from seismic wide-angle data (2009)
    Associated volumes
    Details Availability
    In: Geophysical journal international, Oxford : Oxford Univ. Press, 1958, 178(2009), 2, Seite 1112-1131, 1365-246X
    In: volume:178
    In: year:2009
    In: number:2
    In: pages:1112-1131
    Type of Medium: Online Resource
    Pages: graph. Darst
    ISSN: 1365-246X
    DOI: 10.1111/j.1365-246X.2009.04208.x
    Language: English
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  • 4
    Online Resource
    Online Resource
    Crustal structure of the Mid-Atlantic Ridge at 5° South : two contrasting spreading segments (2006)
    Kiel
    Details Availability
    Keywords: Hochschulschrift ; Mittelatlantischer Rücken ; Ozeanische Erdkruste
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource ( 217Seiten = 36MB) , Ill., graph. Darst., Kt.
    URL: https://oceanrep.geomar.de/id/eprint/5802/
    Language: English
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  • 5
    Book
    Book
    CONGO Compilation of seismic wide-angle data : RV METEOR Cruise M56 Congo 2002, Gashydrate Research - GEOMAR Data Report (2003)
    Kiel : GEOMAR
    Details Availability
    Keywords: Forschungsbericht
    Type of Medium: Book
    Pages: 43 Seiten
    Language: English
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  • 6
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    The impact of fluid advection on gas hydrate stability: Investigations at sites of methane seepage offshore Costa Rica (2014)
    Elsevier
    In:  Earth and Planetary Science Letters, 401 . pp. 95-109.
    Details
    Publication Date: 2017-03-13
    Description: Highlights • We map out the 3D extent of gas hydrate stability beneath two methane seep sites. • Focused fluid flow has sustained large-scale gas hydrate instability. • The two seeps likely have the same deep fluid source, despite shallow differences. • Fault networks influenced the initiation of advective flow through the hydrate system. • Ongoing flow towards the seeps is likely sustained by networks of hydrofractures. Abstract Fluid flow through marine sediments drives a wide range of processes, from gas hydrate formation and dissociation, to seafloor methane seepage including the development of chemosynthetic ecosystems, and ocean acidification. Here, we present new seismic data that reveal the 3D nature of focused fluid flow beneath two mound structures on the seafloor offshore Costa Rica. These mounds have formed as a result of ongoing seepage of methane-rich fluids. We show the spatial impact of advective heat flow on gas hydrate stability due to the channelled ascent of warm fluids towards the seafloor. The base of gas hydrate stability (BGHS) imaged in the seismic data constrains peak heat flow values to View the MathML source∼60 mWm−2 and View the MathML source∼70 mWm−2 beneath two separate seep sites known as Mound 11 and Mound 12, respectively. The initiation of pronounced fluid flow towards these structures was likely controlled by fault networks that acted as efficient pathways for warm fluids ascending from depth. Through the gas hydrate stability zone, fluid flow has been focused through vertical conduits that we suggest developed as migrating fluids generated their own secondary permeability by fracturing strata as they forced their way upwards towards the seafloor. We show that Mound 11 and Mound 12 (about 1 km apart on the seafloor) are sustained by independent fluid flow systems through the hydrate system, and that fluid flow rates across the BGHS are probably similar beneath both mounds. 2D seismic data suggest that these two flow systems might merge at approximately 1 km depth, i.e. much deeper than the BGHS. This study provides a new level of detail and understanding of how channelled, anomalously-high fluid flow towards the seafloor influences gas hydrate stability. Thus, gas hydrate systems have good potential for quantifying the upward flow of subduction system fluids to seafloor seep sites, since the fluids have to interact with and leave their mark on the hydrate system before reaching the seafloor.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.epsl.2014.05.045
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Lower plate structure and upper plate deformational segmentation at the Sunda-Banda arc transition, Indonesia (2010)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 115 (B8). B08107.
    Details
    Publication Date: 2018-02-27
    Description: The Sunda‐Banda arc transition at the eastern termination of the Sunda margin (Indonesia) represents a unique natural laboratory to study the effects of lower plate variability on upper plate deformational segmentation. Neighboring margin segments display a high degree of structural diversity of the incoming plate (transition from an oceanic to a continental lower plate, presence/absence of an oceanic plateau, variability of subducting seafloor morphology) as well as a wide range of corresponding fore‐arc structures, including a large sedimentary basin and an accretionary prism/outer arc high of variable size and shape. Here, we present results of a combined analysis of seismic wide‐angle refraction, multichannel streamer and gravity data recorded in two trench normal corridors located offshore the islands of Lombok (116°E) and Sumba (119°E). On the incoming plate, the results reveal a 8.6–9.0 km thick oceanic crust, which is progressively faulted and altered when approaching the trench, where upper mantle velocities are reduced to ∼7.5 km/s. The outer arc high, located between the trench and the fore‐arc basin, is characterized by sedimentary‐type velocities (Vp 〈 5.5 km/s) down to the top of the subducting slab (∼13 km depth). The oceanic slab can be traced over 70–100 km distance beneath the fore arc. A shallow serpentinized mantle wedge at ∼16 km depth offshore Lombok is absent offshore Sumba, where our models reveal the transition to the collisional regime farther to the east and to the Sumba block in the north. Our results allow a detailed view into the complex structure of both the deeper and shallower portions of the eastern Sunda margin.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2009JB006713
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  • 8
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    Bathymetry of the Indonesian Sunda margin-relating morphological features of the upper plate slopes to the location and extent of the seismogenic zone (2010)
    Copernicus Publications
    In:  Natural Hazards and Earth System Sciences, 10 (9). pp. 1899-1911.
    Details
    Publication Date: 2019-09-23
    Description: Earthquake history shows that the Sunda subduction zone of the Indonesian margin produces great earthquakes offshore Sumatra, whereas earthquakes of comparable magnitude are lacking offshore Java and the Lesser Sunda islands. Morphological structures in multibeam bathymetric data across the forearc relate with the extent of the seismogenic zone. Its updip limit corresponds to the slope break, most distinct off Java and Lesser Sunda islands, where we find coincident narrow, uniform, continuous outer arc ridges. Their landward termination and a shallow upper plate mantle mark the downdip limit of the seismogenic zone. In contrast the outer arc ridges off Sumatra are wider and partly elevated above sea level forming the forearc islands. The downdip limit of the seismogenic zone coincides with a deeper upper plate mantle. Sunda Strait marks a transition zone between the Sumatra and Java margins. We find the differences along the Sunda margin, especially the wider extent of the seismogenic zone off Sumatra, producing larger earthquakes, to result from the interaction of different age and subduction direction of the oceanic plate. We attribute a major role to the sediment income and continental/oceanic upper plate nature of Sumatra/Java influencing the composition and deformation style along the forearc and subduction fault.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.5194/nhess-10-1899-2010
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  • 9
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    Structure, evolution and tectonic activity of the eastern Sunda forearc, Indonesia, from marine seismic investigations (2011)
    Elsevier
    In:  Tectonophysics, 508 (1-4). pp. 6-21. Date online first: 2011
    Details
    Publication Date: 2019-09-23
    Description: Forearc structures of the eastern Sunda Arc are studied by new multichannel reflection seismic profiling. We image a high along-strike variability of the subducting oceanic plate, the interface between subducting and overriding plate, the accretionary wedge, the outer arc high and forearc basins. We highlight ongoing tectonic activity of the entire outer arc high: active out-of-sequence thrust faults connecting the plate interface with the seafloor, slope basins showing tilted sedimentary sequences on the outer arc high, vertical displacement of young seafloor sediments, and tilted sedimentary sequences in the Lombok forearc basin. While frontal accretion plays a minor role, the growth of the outer arc high is mainly attributed to oceanic sediments and crustal fragments, which are attached to the base of the upper plate and recycled within the forearc. We image ongoing large-scale duplex formation of the oceanic crust. The incoming oceanic crust is dissected by normal faulting into 5–10 km wide blocks within a 50–70 km wide belt seaward of the deep sea trench. These blocks determine the geometry and evolution of duplexes attached to the base of the overriding plate landward of the trench. Long-lasting and ongoing subsidence of the Lombok Basin is documented by distinct seismic sequences. In the Lombok Basin we image mud diapirs, fed from deeply buried sediments which may have been mobilized by rising fluids. We propose a wrench fault system in the eastern Lombok forearc basin that decouples the subduction regime of the Sunda Arc from the continent–island arc collision regime of the western Banda Arc. The observed tectonic activity of the entire forearc system reflects a high earthquake and tsunami hazard, similar to the western part of the Sunda Arc.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.tecto.2010.06.008
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    The Sunda-Banda Arc transition: New Insights From Marine Wide-Angle Seismic Data Offshore Eastern Indonesia (2008)
    In:  [Poster] In: EGU General Assembly, 13.-18.04, Vienna, Austria .
    Details
    Publication Date: 2012-02-23
    Type: Conference or Workshop Item , NonPeerReviewed
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    OceanRep: Poster
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