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  • 1
    Publication Date: 2018-12-14
    Description: Highlights • Northern Hispaniola Margin is studied with new high-resolution bathymetry and vintage seismic data. • Northern Hispaniola Deformed Belt forms an active N-verging fold-and-thrust imbricate system. • Gravity failures are frequent features in the Northern Hispaniola Margin and Bahamas Banks slope. • Oblique collision accelerates the Bahamas Carbonate Province collapse and retreat. • New observations help the assessment of tsunami hazards in the Northern Caribbean region. Abstract The northern margin of Hispaniola records the oblique collision/underthrusting of the Bahamas Carbonate Province with the island-arc. Due to the collision, northern Hispaniola has suffered several natural disasters caused by major earthquakes and tsunamis, such as the historic earthquake of 1842, the tsunami caused by earthquake-driven slumping in 1918 in the Mona Passage, the seismic crisis of 1943–1953 with five events of M 〉 7.0 or the seismic crisis of 2003 with a main shock of M6.3 and a large aftershock of M5.3. Using new swath multibeam bathymetry data and vintage single- and multi-channel seismic profiles, we have performed a regional scale analysis and interpretation of the shallow surface and active processes along the northern margin of the Dominican Republic. We have identified three morphostructural provinces: a) the Bahamas Banks, b) the Hispaniola Trench and c) the Insular Margin, which are divided into two tectonic domains, the Collision Domain and Underthrusting Domain. The southern slope of the Bahamas Carbonate Province shows a very irregular morphology produced by active erosive processes and normal dip-slip faulting, evidence of an extensional tectonic regime and margin collapse. This collapse is of major extent in the Oblique Collision Domain where there are erosive and fault escarpments with higher dip-slip fault throws. The Hispaniola Trench, is formed by the Caicos and Hispaniola basins in the underthrusting domain, and by the Santisima Trinidad and Navidad basins in the Oblique Collision Domain. They have a flat seafloor with a sedimentary filling of variable thickness consisting of horizontal or sub-horizontal turbiditic levels. The turbiditic fill mostly proceeds from the island arc through wide channels and canyons, which transports sediment from the shelf and upper slope. The Insular Margin comprises the Insular Shelf and the Insular Slope. The active processes are generated on the Insular Slope where the Northern Hispaniola Deformed Belt is developed. This Deformed Belt shows a very irregular morphology, with a WNW-ESE trending N verging imbricate thrust-and fold system. This system is the result of the adjustment of the oblique collision/underthrusting between the North American plate and the Caribbean plate. In the Oblique Underthrusting Domain the along-strike development of the imbricate system is highly variable forming salients and recesses. This variability is due to along-strike changes in the sediment thickness of the Hispaniola Trench, as well as to the variable topography of the underthrusting Bahamas Carbonate Province. In the Oblique Collision Domain, the morphology of the Insular Slope and the development of the Deformed Belt deeply change. The imbricate system is barely inferred and lies upslope. These changes are due to the active collision of Bahamas Carbonate Province with the Insular Margin where the spurs are indented against the Insular Margin. Throughout the entire area studied, gravitational instabilities have been observed, especially on the Insular Margin and to a lesser extent on the southern slope of the Bahamas Carbonate Province. These instabilities are a direct consequence of the active underthrusting/collision process. We have mapped large individual slumps north of Puerto Plata in the Oblique Underthrusting Domain and zones of major slumps in the Oblique Collision Domain. These evidences of active processes must be considered as near-field sources in future studies on the assessment of tsunami hazards in the region.
    Type: Article , PeerReviewed
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  • 2
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Existing models assume that the thickened crust beneath seamounts is the result of a surface volcanic load flexing an elastic plate. New results suggest that flexed oceanic crust beneath the Hawaiian–Emperor seamount chain is underlain by a 4-km thick deep crustal body. We intepret the body ...
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 317 (1985), S. 421-424 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Figure 1 shows common mid-point (CMP) multichannel seismic reflection line 314 of the flexural moat NNE of Oahu, Hawaii. Individual traces were demuxed, gathered and stacked in 50-m bins7. Predictive deconvolution was applied after stacking and the data were bandpass filtered (6-30 Hz). Although ...
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2016-12-29
    Description: Earthquake data from two short-period ocean-bottom seismometer (OBS) networks deployed for over a year on the continental slope off New York and southern New England were used to evaluate seismicity and ground motions along the continental margin. Our OBS networks located only one earthquake of M c ~1.5 near the shelf edge during six months of recording, suggesting that seismic activity ( M Lg 〉3.0) of the margin as far as 150–200 km offshore is probably successfully monitored by land stations without the need for OBS deployments. The spectral acceleration from two local earthquakes recorded by the OBS was found to be generally similar to the acceleration from these earthquakes recorded at several seismic stations on land and to hybrid empirical acceleration relationships for eastern North America. Therefore, the seismic attenuation used for eastern North America can be extended in this region at least to the continental slope. However, additional offshore studies are needed to verify these preliminary conclusions.
    Print ISSN: 0895-0695
    Electronic ISSN: 1938-2057
    Topics: Geosciences
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  • 5
    Publication Date: 2016-06-30
    Description: We explore the effects of earthquake frequency and sedimentation rate on submarine slope stability by extracting correlations between morphological and geological parameters in 10 continental margins. Slope stability increases with increasing frequency of earthquakes and decreasing sedimentation rate. This increase in stability is nonlinear (power law with b 〈 0.5), accelerating with decreasing interseismic sediment accumulation. The correlation is interpreted as evidence for sediment densification and associated shear strength gain induced by repeated seismic shaking. Outliers to this correlation likely identify margins where tectonic activity leads to relatively rapid oversteepening of the slope.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
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  • 6
    Publication Date: 2002-06-01
    Description: The Seattle fault, a large, seismically active, east-west-striking fault zone under Seattle, is the best-studied fault within the tectonically active Puget Lowland in western Washington, yet its subsurface geometry and evolution are not well constrained. We combine several analysis and modeling approaches to study the fault geometry and evolution, including depth-converted, deep-seismic-reflection images, P-wave-velocity field, gravity data, elastic modeling of shoreline uplift from a late Holocene earthquake, and kinematic fault restoration. We propose that the Seattle thrust or reverse fault is accompanied by a shallow, antithetic reverse fault that emerges south of the main fault. The wedge enclosed by the two faults is subject to an enhanced uplift, as indicated by the boxcar shape of the shoreline uplift from the last major earthquake on the fault zone. The Seattle Basin is interpreted as a flexural basin at the footwall of the Seattle fault zone. Basin stratigraphy and the regional tectonic history lead us to suggest that the Seattle fault zone initiated as a reverse fault during the middle Miocene, concurrently with changes in the regional stress field, to absorb some of the north-south shortening of the Cascadia forearc. Kingston Arch, 30 km north of the Seattle fault zone, is interpreted as a more recent disruption arising within the basin, probably due to the development of a blind reverse fault.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences
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  • 7
    Publication Date: 2018-05-23
    Description: The Queen Charlotte Fault defines the Pacific–North America transform plate boundary in western Canada and southeastern Alaska for c. 900 km. The entire length of the fault is submerged along a continental margin dominated by Quaternary glacial processes, yet the geomorphology along the margin has never been systematically examined due to the absence of high-resolution seafloor mapping data. Hence the geological processes that influence the distribution, character and timing of mass transport events and their associated hazards remain poorly understood. Here we develop a classification of the first-order shape of the continental shelf, slope and rise to examine potential relationships between form and process dominance. We found that the margin can be split into six geomorphic groups that vary smoothly from north to south between two basic end-members. The northernmost group (west of Chichagof Island, Alaska) is characterized by concave-upwards slope profiles, gentle slope gradients (〈6°) and relatively low along-strike variance, all features characteristic of sediment-dominated siliciclastic margins. Dendritic submarine canyon/channel networks and retrogressive failure complexes along relatively gentle slope gradients are observed throughout the region, suggesting that high rates of Quaternary sediment delivery and accumulation played a fundamental part in mass transport processes. Individual failures range in area from 0.02 to 70 km 2 and display scarp heights between 10 and 250 m. Transpression along the Queen Charlotte Fault increases southwards and the slope physiography is thus progressively more influenced by regional-scale tectonic deformation. The southernmost group (west of Haida Gwaii, British Columbia) defines the tectonically dominated end-member: the continental slope is characterized by steep gradients (〉20°) along the flanks of broad, margin-parallel ridges and valleys. Mass transport features in the tectonically dominated areas are mostly observed along steep escarpments and the larger slides (up to 10 km 2 ) appear to be failures of consolidated material along the flanks of tectonic features. Overall, these observations highlight the role of first-order margin physiography on the distribution and type of submarine landslides expected to occur in particular morphological settings. The sediment-dominated end-member allows for the accumulation of under-consolidated Quaternary sediments and shows larger, more frequent slides; the rugged physiography of the tectonically dominated end-member leads to sediment bypass and the collapse of uplifted tectonic features. The maximum and average dimensions of slides are an order of magnitude smaller than those of slides observed along other (passive) glaciated margins. We propose that the general patterns observed in slide distribution are caused by the interplay between tectonic activity (long- and short-term) and sediment delivery. The recurrence (〈100 years) of M 〉 7 earthquakes along the Queen Charlotte Fault may generate small, but frequent, failures of under-consolidated Quaternary sediments within the sediment-dominated regions. By contrast, the tectonically dominated regions are characterized by the bypass of Quaternary sediments to the continental rise and the less frequent collapse of steep, uplifted and consolidated sediments.
    Print ISSN: 0305-8719
    Electronic ISSN: 2041-4927
    Topics: Geosciences
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  • 8
    Publication Date: 2017-04-01
    Description: Extraordinary marine inundation scattered clasts southward on the island of Anegada, 120 km south of the Puerto Rico Trench, sometime between 1200 and 1480 calibrated years (cal yr) CE. Many of these clasts were likely derived from a fringing reef and from the sandy flat that separates the reef from the island’s north shore. The scattered clasts include no fewer than 200 coral boulders, mapped herein for the first time and mainly found hundreds of meters inland. Many of these are complete colonies of the brain coral Diploria strigosa . Other coral species represented include Orbicella (formerly Montastraea ) annularis , Porites astreoides , and Acropora palmata . Associated bioclastic carbonate sand locally contains articulated cobble-size valves of the lucine Codakia orbicularis and entire conch shells of Strombus gigas , mollusks that still inhabit the sandy shallows between the island’s north shore and a fringing reef beyond. Imbricated limestone slabs are clustered near some of the coral boulders. In addition, fields of scattered limestone boulders and cobbles near sea level extend mainly southward from limestone sources as much as 1 km inland. Radiocarbon ages have been obtained from 27 coral clasts, 8 lucine valves, and 3 conch shells. All these additional ages predate 1500 cal yr CE, all but 2 are in the range 1000–1500 cal yr CE, and 16 of 22 brain coral ages cluster in the range 1200–1480 cal yr CE. The event marked by these coral and mollusk clasts likely occurred in the last centuries before Columbus (before 1492 CE). The pre-Columbian deposits surpass Anegada’s previously reported evidence for extreme waves in post-Columbian time. The coarsest of the modern storm deposits consist of coral rubble that lines the north shore and sandy fans on the south shore; neither of these storm deposits extends more than 50 m inland. More extensive overwash, perhaps by the 1755 Lisbon tsunami, is marked primarily by a sheet of sand and shells found mainly below sea level beneath the floors of modern salt ponds. This sheet extends more than 1 km southward from the north shore and dates to the interval 1650–1800 cal yr CE. Unlike the pre-Columbian deposits, it lacks coarse clasts from the reef or reef flat; its shell assemblage is instead dominated by cerithid gastropods that were merely stirred up from a marine pond in the island’s interior. In their inland extent and clustered pre-Columbian ages, the coral clasts and associated deposits suggest extreme waves unrivaled in recent millennia at Anegada. Bioclastic sand coats limestone 4 m above sea level in areas 0.7 and 1.3 km from the north shore. A coral boulder of nearly 1 m 3 is 3 km from the north shore by way of an unvegetated path near sea level. As currently understood, the extreme flooding evidenced by these and other clasts represents either an extraordinary storm or a tsunami of nearby origin. The storm would need to have produced tsunami-like bores similar to those of 2013 Typhoon Haiyan in the Philippines. Normal faults and a thrust fault provide nearby tsunami sources along the eastern Puerto Rico Trench.
    Electronic ISSN: 1553-040X
    Topics: Geosciences
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  • 9
    Publication Date: 2012-02-01
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
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  • 10
    Publication Date: 2010-05-14
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
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