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  • Seismic reflection  (2)
  • Slab tear  (2)
  • Submarine landslides  (2)
  • 1
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    Geomorphic characterization of the U.S. Atlantic continental margin (2013)
    Elsevier B.V.
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    Publikationsdatum: 2022-05-25
    Beschreibung: This paper is not subject to U.S. copyright. The definitive version was published in Marine Geology 338 (2013): 46–63, doi:10.1016/j.margeo.2012.12.008.
    Beschreibung: The increasing volume of multibeam bathymetry data collected along continental margins is providing new opportunities to study the feedbacks between sedimentary and oceanographic processes and seafloor morphology. Attempts to develop simple guidelines that describe the relationships between form and process often overlook the importance of inherited physiography in slope depositional systems. Here, we use multibeam bathymetry data and seismic reflection profiles spanning the U.S. Atlantic outer continental shelf, slope and rise from Cape Hatteras to New England to quantify the broad-scale, across-margin morphological variation. Morphometric analyses suggest the margin can be divided into four basic categories that roughly align with Quaternary sedimentary provinces. Within each category, Quaternary sedimentary processes exerted heavy modification of submarine canyons, landslide complexes and the broad-scale morphology of the continental rise, but they appear to have preserved much of the pre-Quaternary, across-margin shape of the continental slope. Without detailed constraints on the substrate structure, first-order morphological categorization the U.S. Atlantic margin does not provide a reliable framework for predicting relationships between form and process.
    Beschreibung: This work was funded by the USGS Mendenhall Postdoctoral Fellowship Program and the U.S. Nuclear Regulatory Commission.
    Schlagwort(e): Passive margin ; Continental slope ; Classification ; Submarine canyon ; Seismic reflection ; Multibeam bathymetry
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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  • 2
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    Geologic controls on submarine slope failure along the central U.S. Atlantic margin : insights from the Currituck Slide Complex (2018)
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    Publikationsdatum: 2022-05-25
    Beschreibung: © The Author(s), 2016. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marine Geology 385 (2017): 114-130, doi:10.1016/j.margeo.2016.10.007.
    Beschreibung: Multiple styles of failure, ranging from densely spaced, mass transport driven canyons to the large, slab-type slope failure of the Currituck Slide, characterize adjacent sections of the central U.S. Atlantic margin that appear to be defined by variations in geologic framework. Here we use regionally extensive, deep penetration multichannel seismic (MCS) profiles to reconstruct the influence of the antecedent margin physiography on sediment accumulation along the central U.S. Atlantic continental shelf-edge, slope, and uppermost rise from the Miocene to Present. These data are combined with highresolution sparker MCS reflection profiles and multibeam bathymetry data across the Currituck Slide complex. Pre-Neogene allostratigraphic horizons beneath the slope are generally characterized by low gradients and convex downslope profiles. This is followed by the development of thick, prograded deltaic clinoforms during the middle Miocene. Along-strike variations in morphology of a regional unconformity at the top of this middle Miocene unit appear to have set the stage for differing styles of mass transport along the margin. Areas north and south of the Currituck Slide are characterized by oblique margin morphology, defined by an angular shelf-edge and a relatively steep (〉8°), concave slope profile. Upper slope sediment bypass, closely spaced submarine canyons, and small, localized landslides confined to canyon heads and sidewalls characterize these sectors of the margin. In contrast, the Currituck region is defined by a sigmoidal geometry, with a rounded shelf-edge rollover and gentler slope gradient (〈6°). Thick (〉800 m), regionally continuous stratified slope deposits suggest the low gradient Currituck region was a primary depocenter for fluvial inputs during multiple sea level lowstands. These results imply that the rounded, gentle slope physiography developed during the middle Miocene allowed for a relatively high rate of subsequent sediment accumulation, thus providing a mechanism for compaction–induced overpressure that preconditioned the Currituck region for failure. Detailed examination of the regional geological framework illustrates the importance of both sediment supply and antecedent slope physiography in the development of large, potentially unstable depocenters along passive margins.
    Beschreibung: The U.S. Geological Survey, the U.S. Nuclear Regulatory Commission and Coastal Carolina University funded this research.
    Schlagwort(e): Submarine landslides ; Multichannel seismic data ; U.S. Atlantic margin ; Geomorphology ; Unconformity ; Sediment supply ; Stratigraphy ; Isopach maps ; Slope gradient ; Accommodation space
    Repository-Name: Woods Hole Open Access Server
    Materialart: Preprint
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  • 3
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    Slab tears and intermediate‐depth seismicity (2018)
    American Geophysical Union
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 40 (2013): 4244-4248, doi:10.1002/grl.50830.
    Beschreibung: Active tectonic regions where plate boundaries transition from subduction to strike slip can take several forms, such as triple junctions, acute, and obtuse corners. Well‐documented slab tears that are associated with high rates of intermediate‐depth seismicity are considered here: Gibraltar arc, the southern and northern ends of the Lesser Antilles arc, and the northern end of Tonga trench. Seismicity at each of these locations occurs, at times, in the form of swarms or clusters, and various authors have proposed that each marks an active locus of tear propagation. The swarms and clusters start at the top of the slab below the asthenospheric wedge and extend 30–60 km vertically downward within the slab. We propose that these swarms and clusters are generated by fluid‐related embrittlement of mantle rocks. Focal mechanisms of these swarms generally fit the shear motion that is thought to be associated with the tearing process.
    Schlagwort(e): Slab tear ; Intermediate seismicity ; Subduction corner
    Repository-Name: Woods Hole Open Access Server
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  • 4
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    Vertical motions of the Puerto Rico Trench and Puerto Rico and their cause (2005)
    American Geophysical Union
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    Publikationsdatum: 2022-05-25
    Beschreibung: This paper is not subject to U.S. copyright. Published in 2005 by the American Geophysical Union. The definitive version was published in Journal of Geophysical Research 110 (2005): B06404, doi:10.1029/2004JB003459.
    Beschreibung: The Puerto Rico trench exhibits great water depth, an extremely low gravity anomaly, and a tilted carbonate platform between (reconstructed) elevations of +1300 m and −4000 m. I argue that these features are manifestations of large vertical movements of a segment of the Puerto Rico trench, its forearc, and the island of Puerto Rico that took place 3.3 m.y. ago over a time period as short as 14–40 kyr. I explain these vertical movements by a sudden increase in the slab's descent angle that caused the trench to subside and the island to rise. The increased dip could have been caused by shearing or even by a complete tear of the descending North American slab, although the exact nature of this deformation is unknown. The rapid (14–40 kyr) and uniform tilt along a 250 km long section of the trench is compatible with scales of mantle flow and plate bending. The proposed shear zone or tear is inferred from seismic, morphological, and gravity observations to start at the trench at 64.5°W and trend southwestwardly toward eastern Puerto Rico. The tensile stresses necessary to deform or tear the slab could have been generated by increased curvature of the trench following a counterclockwise rotation of the upper plate and by the subduction of a large seamount.
    Schlagwort(e): Dynamic topography ; Slab tear ; Puerto Rico trench ; Caribbean plate ; Challenger Deep ; Seamount subduction
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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  • 5
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    Extension in Mona Passage, Northeast Caribbean (2010)
    Elsevier B.V.
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    Publikationsdatum: 2022-05-25
    Beschreibung: This paper is not subject to U.S. copyright. The definitive version was published in Tectonophysics 493 (2010): 74-92, doi:10.1016/j.tecto.2010.07.002.
    Beschreibung: As shown by the recent Mw 7.0 Haiti earthquake, intra-arc deformation, which accompanies the subduction process, can present seismic and tsunami hazards to nearby islands. Spatially-limited diffuse tectonic deformation within the Northeast Caribbean Plate Boundary Zone likely led to the development of the submerged Mona Passage between Puerto Rico and the Dominican Republic. GPS geodetic data and a moderate to high level of seismicity indicate that extension within the region is ongoing. Newly-collected high-resolution multibeam bathymetry and multi-channel seismic reflection profiles and previously-collected samples are used here to determine the tectonic evolution of the Mona Passage intra-arc region. The passage is floored almost completely by Oligocene–Pliocene carbonate platform strata, which have undergone submarine and subaerial erosion. Structurally, the passage is characterized by W- to NNW-trending normal faults that offset the entire thickness of the Oligo–Pliocene carbonate platform rocks. The orientation of these faults is compatible with the NE-oriented extension vector observed in GPS data. Fault geometry best fits an oblique extension model rather than previously proposed single-phase, poly-phase, bending-moment, or rotation extension models. The intersection of these generally NW-trending faults in Mona Passage with the N–S oriented faults of Mona Canyon may reflect differing responses of the brittle upper-crust, along an arc–forearc rheological boundary, to oblique subduction along the Puerto Rico trench. Several faults within the passage, if ruptured completely, are long enough to generate earthquakes with magnitudes on the order of Mw 6.5–7.
    Schlagwort(e): Bathymetry ; Seismic reflection ; Earthquakes ; Oblique extension ; Geomorphology
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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  • 6
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    Assessment of tsunami hazard to the U.S. Atlantic margin (2014)
    Elsevier
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    Publikationsdatum: 2022-05-26
    Beschreibung: This paper is not subject to U.S. copyright. The definitive version was published in Marine Geology 353 (2014): 31-54, doi:10.1016/j.margeo.2014.02.011.
    Beschreibung: Tsunami hazard is a very low-probability, but potentially high-risk natural hazard, posing unique challenges to scientists and policy makers trying to mitigate its impacts. These challenges are illustrated in this assessment of tsunami hazard to the U.S. Atlantic margin. Seismic activity along the U.S. Atlantic margin in general is low, and confirmed paleo-tsunami deposits have not yet been found, suggesting a very low rate of hazard. However, the devastating 1929 Grand Banks tsunami along the Atlantic margin of Canada shows that these events continue to occur. Densely populated areas, extensive industrial and port facilities, and the presence of ten nuclear power plants along the coast, make this region highly vulnerable to flooding by tsunamis and therefore even low-probability events need to be evaluated. We can presently draw several tentative conclusions regarding tsunami hazard to the U.S. Atlantic coast. Landslide tsunamis likely constitute the biggest tsunami hazard to the coast. Only a small number of landslides have so far been dated and they are generally older than 10,000 years. The geographical distribution of landslides along the margin is expected to be uneven and to depend on the distribution of seismic activity along the margin and on the geographical distribution of Pleistocene sediment. We do not see evidence that gas hydrate dissociation contributes to the generation of landslides along the U.S. Atlantic margin. Analysis of landslide statistics along the fluvial and glacial portions of the margin indicate that most of the landslides are translational, were probably initiated by seismic acceleration, and failed as aggregate slope failures. How tsunamis are generated from aggregate landslides remains however, unclear. Estimates of the recurrence interval of earthquakes along the continental slope may provide maximum estimates for the recurrence interval of landslide along the margin. Tsunamis caused by atmospheric disturbances and by coastal earthquakes may be more frequent than those generated by landslides, but their amplitudes are probably smaller. Among the possible far-field earthquake sources, only earthquakes located within the Gulf of Cadiz or west of the Tore-Madeira Rise are likely to affect the U.S. coast. It is questionable whether earthquakes on the Puerto Rico Trench are capable of producing a large enough tsunami that will affect the U.S. Atlantic coast. More information is needed to evaluate the seismic potential of the northern Cuba fold-and-thrust belt. The hazard from a volcano flank collapse in the Canary Islands is likely smaller than originally stated, and there is not enough information to evaluate the magnitude and frequency of flank collapse from the Azores Islands. Both deterministic and probabilistic methods to evaluate the tsunami hazard from the margin are available for application to the Atlantic margin, but their implementation requires more information than is currently available.
    Beschreibung: The work was funded by the U.S.-NRC Job Code V6166: Tsunami Landslide Source Probability and Potential Impact on New and Existing Power Plants.
    Schlagwort(e): Submarine landslides ; Meteo-tsunami ; Earthquakes and landslides ; Probabilistic hazard assessment
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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