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A Levander - One of the best experts on this subject based on the ideXlab platform.
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the caribbean south american Plate Boundary at 65 w results from wide angle seismic data
Journal of Geophysical Research, 2010Co-Authors: Maximiliano Bezada, C A Zelt, M B Magnani, Michael Schmitz, A LevanderAbstract:[1] We present the results of the analysis of new wide-angle seismic data across the Caribbean–South American Plate Boundary in eastern Venezuela at about 65°W. The ∼500 km long profile crosses the Boundary in one of the few regions dominated by extensional structures, as most of the southeastern Caribbean margin is characterized by the presence of fold and thrust belts. A combination of first-arrival traveltime inversion and simultaneous inversion of PmP and Pn arrivals was used to develop a P wave velocity model of the crust and the uppermost mantle. At the main strike-slip fault system, we image the Cariaco Trough, a major pull-apart basin along the Plate Boundary. The crust under the Southern Caribbean Deformed Belt exhibits a thickness of ∼15 km, suggesting that the Caribbean Large Igneous Province extends to this part of the Caribbean Plate. The velocity structures of basement highs and offshore sedimentary basins imaged by the profile are comparable to those of features found in other parts of the margin, suggesting similarities in their tectonic history. We do not image an abrupt change in Moho depth or velocity structure across the main strike-slip system, as has been observed elsewhere along the margin. It is possible that a terrane of Caribbean island arc origin was accreted to South America at this site and was subsequently bisected by the strike-slip fault system. The crust under the continental portion of the profile is thinner than observed elsewhere along the margin, possibly as a result of thinning during Jurassic rifting.
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upper mantle structure beneath the caribbean south american Plate Boundary from surface wave tomography
Journal of Geophysical Research, 2009Co-Authors: Meghan S Miller, A Levander, Fenglin NiuAbstract:[1] We have measured shear wave velocity structure of the crust and upper mantle of the Caribbean-South American Boundary region by analysis of fundamental mode Rayleigh waves in the 20- to 100-s period band recorded at the BOLIVAR/GEODINOS stations from 2003 to 2005. The model shows lateral variations that primarily correspond to tectonic provinces and boundaries. A clear linear velocity change parallels the Plate bounding dextral strike-slip fault system along the northern coast of Venezuela, illustrating the differences between the South American continental lithosphere, the Venezuelan archipelago, and the Caribbean oceanic lithosphere. At depths up to 120 km beneath the Venezuelan Andes and the Maracaibo block, there is evidence of underthrusting of the Caribbean Plate, but there is no other evidence of subduction of the Caribbean Plate beneath the South American Plate. In eastern Venezuela, linear crustal low velocities are associated with the fold and thrust belts whereas as higher crustal velocities are imaged in the Guayana shield lithosphere. The subducting oceanic part of the South American Plate is imaged beneath the Antilles arc. The surface wave images combined with seismicity data suggest shear tearing of the oceanic lithosphere away from the buoyant continental South American Plate offshore of northeastern Venezuela. The continental lithosphere south of the slab tear is bent down toward the Plate Boundary in response to the propagating tear in the lithosphere. We interpret a nearly vertical low-velocity ‘‘column’’ west of the tear centered beneath the Cariaco Basin, with three-dimensional asthenospheric flow around the southern edge of the subducting oceanic lithosphere, with the asthenosphere escaping from beneath continental South America and rising into the Plate Boundary zone. The complex Plate Boundary structure is best examined in three dimensions. We discuss the new surface wave tomographic inversion in the context of results from other researchers including local seismicity, teleseismic shear wave splits, and interpretations from active source profiling.
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negligible convergence and lithospheric tearing along the caribbean south american Plate Boundary at 64 w
Tectonics, 2008Co-Authors: S A Clark, A Levander, M B Magnani, C A ZeltAbstract:[1] Prior studies of the Caribbean–South American Plate Boundary have suffered from poor constraint on the structure of the crust and uppermost mantle. We use a recent wide-angle velocity model from the Broadband Ocean-Land Investigation of Venezuela and the Antilles arc Region project to constrain new seismic reflection data and previously published line drawing interpretations of the Caribbean–South American Plate Boundary at 64°W. Though commonly characterized as obliquely convergent, we determine that convergence is negligible in our study area. Previous estimates of Miocene to present north-south shortening onshore eastern Venezuela have commonly been 115 km or higher, but we constrain shortening to ∼35 km onshore, with an additional ∼30 km offshore. With such minor convergence, we conclude that uplift and basin subsidence in eastern Venezuela does not derive from typical collisional orogeny. Instead, the largely vertical tectonics likely result from mantle dynamics associated with an eastward propagating, near-vertical tear in the lithosphere along the former passive margin.
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characterizing the caribbean south american Plate Boundary at 64 w using wide angle seismic data
Journal of Geophysical Research, 2008Co-Authors: C A Zelt, M B Magnani, Stephen Clark, A LevanderAbstract:[1] We present wide-angle velocity modeling results from profile 64°W of the Broadband Ocean-Land Investigation of Venezuela and the Antilles arc Region (BOLIVAR) project. Line 64W is a 460-km-long, approximately north-south, onshore-offshore reflection/refraction transect located approximately at 64°W longitude. The profile extends across the transform Plate Boundary between the southeastern Caribbean (CAR) and South American (SA) Plates. East of the profile the Plate Boundary bends to the north, and SA subducts beneath CAR. We utilize first-arrival tomography to resolve a smooth velocity field for the sediments and upper/middle crust and then use a layered approach to resolve a sharp velocity contrast for the Moho, simultaneously inverting refracted Pn and reflected PmP arrivals. We image crustal and upper mantle structure across the Plate Boundary zone. We interpret that the strike-slip system that accommodates relative motion between CAR and SA extends near vertically through the entire crust and offsets the Moho. We see no evidence supporting a major component of convergence, and rather than a wide Boundary zone of overlapping lithospheric Plates, we interpret the Plate Boundary to be confined to the 33-km-wide, near-vertical strike-slip system. Previously interpreted thrust faults flanking the strike-slip system appear to be confined to the upper/middle crust and may be related to the detachment of subducting South American lithosphere at the southern terminus of the Lesser Antilles subduction zone east of 64°W.
Paul Mann - One of the best experts on this subject based on the ideXlab platform.
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influence of cumulative convergence on lithospheric thrust fault development and topography along the australian pacific Plate Boundary south of new zealand
Geochemistry Geophysics Geosystems, 2005Co-Authors: Sharon Mosher, Paul Mann, Timothy A Meckel, Millard F CoffinAbstract:The development of faulting and topography resulting from initial convergence within oceanic lithosphere is largely unknown. We explore relationships among convergence, structural development, and topography along ?1500 km of the submarine Australian-Pacific Plate Boundary south of New Zealand, the Macquarie Ridge Complex (MRC). Due to the variable orientation of the Boundary and close proximity of the Australian-Pacific poles of rotation, individual segments of the Plate Boundary have experienced different convergence histories since ?10.95 Ma (Chron 5o). Because interaction along the oceanic extent of the Boundary involves oceanic lithosphere of broadly the same age and therefore thermal structure, structural and morphologic differences can be attributed primarily to variations in angles and rates of convergence with respect to the Plate Boundary orientation since 10.95 Ma. We relate Plate Boundary-normal convergence determined from stage pole rotations to structural development, focusing on transitions from purely strike-slip faulting to partitioned thrust and strike-slip faulting between 47°S and 60°S since 10.95 Ma. Our results indicate that Boundary-normal convergence of ?100 km marks the transition from strike-slip dominated faulting to partitioned underthrusting and strike-slip faulting (incipient subduction). Establishment of subduction at the Puysegur Trench and incipient subduction at the Hjort Trench corresponds to convergence at rates between ?2 and 4 cm/yr, angles >30°, and with durations of at least 10 m.y., resulting in >100 km of Boundary-normal convergence. Anomalous topographic volumes resulting from tectonic deformation are quantified from swath bathymetry and compared to convergence history. Results from analysis of the central MRC suggest that prior to lithospheric-scale thrust faulting, ?100 km of Boundary-normal convergence can be accommodated by crustal deformation (6 km relief from ridge crest to adjacent trough) and strike-slip faulting. Our research supports induced/forced intraoceanic initiation of subduction.
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underthrusting at the hjort trench australian pacific Plate Boundary incipient subduction
Geochemistry Geophysics Geosystems, 2003Co-Authors: Timothy A Meckel, Sharon Mosher, Millard F Coffin, Philip A Symonds, George Bernardel, Paul MannAbstract:[1] The southernmost portion of the Macquarie Ridge Complex (MRC) comprises the Hjort Ridge, Trench, and Plateau, the topographic expression of the Australian-Pacific Plate Boundary south of New Zealand. On the basis of marine geophysical (swath bathymetry/reflectivity, seismic reflection, gravity, magnetic) data, teleseismic data, and gravity modeling, we argue that the Australian Plate is actively underthrusting the Pacific Plate along the Hjort Trench, but self-sustaining subduction does not yet appear to have commenced. We interpret a crustal discontinuity in the Trench as a shallowly dipping thrust splay off a sub-vertical transform fault in the crest of the Hjort Ridge (Hjort Fault). The Hjort Fault separates oceanic crust generated at the Southeast Indian Ridge (SEIR crust), located to the south, from oceanic crust generated at the extinct Australian-Pacific spreading center located to the north (MRC crust). Oblique convergence on the transform has initiated a significant Plate Boundary decollement in the Trench, but our estimate of ∼50 km of underthrusting does not support the existence of an eastwardly dipping Australian slab below ∼20 km depth. For the length of the Hjort Ridge and Trench system, oblique convergence is partitioned between the decollement in the Trench and the Hjort Fault. South of 57.5°S, the trench decollement accommodates thrusting. North of 57.5°S, the Boundary-parallel component of convergence becomes dominant, the Trench gradually shallows, and the trench decollement evolves into a low-angle, oblique-slip fault. The trench decollement and strike-slip system in the Hjort Ridge are structural boundaries that contain tectonic slivers of inferred SEIR crust of the western flank of the Hjort Ridge that currently belong to neither the Australian nor the Pacific Plates.
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paleoseismicity of the north american caribbean Plate Boundary septentrional fault dominican republic
Geology, 1993Co-Authors: Carol S Prentice, Paul Mann, Frederick W Taylor, G S Burr, S ValastroAbstract:The Septentrional fault zone, the major North American-Caribbean Plate-Boundary fault in Hispaniola, is a likely source of large earthquakes in the Dominican Republic. An excavation into a Holocene alluvial fan deposited across the fault in the central Cibao Valley, Dominican Republic, provides evidence that it has been at least 430 yr and probably more than 730 yr since the last ground-rupturing earthquake along this segment of the fault. On the basis of these data and published estimates of the Plate-tectonic slip rate, we propose that the Septentrional fault is a source of high seismic potential in the densely populated and rapidly developing Cibao Valley in the northern Dominican Republic.
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geologic evaluation of Plate kinematic models for the north american caribbean Plate Boundary zone
Tectonophysics, 1991Co-Authors: Christoph Heubeck, Paul MannAbstract:Heubeck, Ch. and Mann, P., 1991. Geologic evaluation of Plate kinematic models for the North American-Caribbean Plate Boundary zone. Tectonophysics, 191: l-26. Four published Plate kinematic models for the present-day North American-Caribbean Plate Boundary predict significantly different fault behavior along this dominantly strike-slip Plate Boundary zone (PBZ). Using a computer graphics system, we compare the deformational pattern predicted by the four kinematic models with geologic and seismic observations along the entire length of the PBZ from Central America to the northern Lesser Antilles. Our results indicate that none of the kinematic models predict all the geologic and seismic observations across the entire PBZ. However, all four models predict mapped fault character and observed earthquake focal mechanisms along certain segments of the PBZ. We conclude that the present-day deformation within the North American-Caribbean Plate Boundary zone cannot be described by rotation about a single pole. Instead, the Caribbean “Plate” appears to be segmented into at least three major “sub-Plates” or blocks, each of which requires an individual pole of rotation to describe its motion relative to the North American Plate. Sub-Plate boundaries correspond to two poorly studied zones of diffuse deformation within the Caribbean Plate (Honduras Depression of Central America and Beata Ridge of the Caribbean Sea).
C A Zelt - One of the best experts on this subject based on the ideXlab platform.
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the caribbean south american Plate Boundary at 65 w results from wide angle seismic data
Journal of Geophysical Research, 2010Co-Authors: Maximiliano Bezada, C A Zelt, M B Magnani, Michael Schmitz, A LevanderAbstract:[1] We present the results of the analysis of new wide-angle seismic data across the Caribbean–South American Plate Boundary in eastern Venezuela at about 65°W. The ∼500 km long profile crosses the Boundary in one of the few regions dominated by extensional structures, as most of the southeastern Caribbean margin is characterized by the presence of fold and thrust belts. A combination of first-arrival traveltime inversion and simultaneous inversion of PmP and Pn arrivals was used to develop a P wave velocity model of the crust and the uppermost mantle. At the main strike-slip fault system, we image the Cariaco Trough, a major pull-apart basin along the Plate Boundary. The crust under the Southern Caribbean Deformed Belt exhibits a thickness of ∼15 km, suggesting that the Caribbean Large Igneous Province extends to this part of the Caribbean Plate. The velocity structures of basement highs and offshore sedimentary basins imaged by the profile are comparable to those of features found in other parts of the margin, suggesting similarities in their tectonic history. We do not image an abrupt change in Moho depth or velocity structure across the main strike-slip system, as has been observed elsewhere along the margin. It is possible that a terrane of Caribbean island arc origin was accreted to South America at this site and was subsequently bisected by the strike-slip fault system. The crust under the continental portion of the profile is thinner than observed elsewhere along the margin, possibly as a result of thinning during Jurassic rifting.
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negligible convergence and lithospheric tearing along the caribbean south american Plate Boundary at 64 w
Tectonics, 2008Co-Authors: S A Clark, A Levander, M B Magnani, C A ZeltAbstract:[1] Prior studies of the Caribbean–South American Plate Boundary have suffered from poor constraint on the structure of the crust and uppermost mantle. We use a recent wide-angle velocity model from the Broadband Ocean-Land Investigation of Venezuela and the Antilles arc Region project to constrain new seismic reflection data and previously published line drawing interpretations of the Caribbean–South American Plate Boundary at 64°W. Though commonly characterized as obliquely convergent, we determine that convergence is negligible in our study area. Previous estimates of Miocene to present north-south shortening onshore eastern Venezuela have commonly been 115 km or higher, but we constrain shortening to ∼35 km onshore, with an additional ∼30 km offshore. With such minor convergence, we conclude that uplift and basin subsidence in eastern Venezuela does not derive from typical collisional orogeny. Instead, the largely vertical tectonics likely result from mantle dynamics associated with an eastward propagating, near-vertical tear in the lithosphere along the former passive margin.
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characterizing the caribbean south american Plate Boundary at 64 w using wide angle seismic data
Journal of Geophysical Research, 2008Co-Authors: C A Zelt, M B Magnani, Stephen Clark, A LevanderAbstract:[1] We present wide-angle velocity modeling results from profile 64°W of the Broadband Ocean-Land Investigation of Venezuela and the Antilles arc Region (BOLIVAR) project. Line 64W is a 460-km-long, approximately north-south, onshore-offshore reflection/refraction transect located approximately at 64°W longitude. The profile extends across the transform Plate Boundary between the southeastern Caribbean (CAR) and South American (SA) Plates. East of the profile the Plate Boundary bends to the north, and SA subducts beneath CAR. We utilize first-arrival tomography to resolve a smooth velocity field for the sediments and upper/middle crust and then use a layered approach to resolve a sharp velocity contrast for the Moho, simultaneously inverting refracted Pn and reflected PmP arrivals. We image crustal and upper mantle structure across the Plate Boundary zone. We interpret that the strike-slip system that accommodates relative motion between CAR and SA extends near vertically through the entire crust and offsets the Moho. We see no evidence supporting a major component of convergence, and rather than a wide Boundary zone of overlapping lithospheric Plates, we interpret the Plate Boundary to be confined to the 33-km-wide, near-vertical strike-slip system. Previously interpreted thrust faults flanking the strike-slip system appear to be confined to the upper/middle crust and may be related to the detachment of subducting South American lithosphere at the southern terminus of the Lesser Antilles subduction zone east of 64°W.
S A Clark - One of the best experts on this subject based on the ideXlab platform.
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negligible convergence and lithospheric tearing along the caribbean south american Plate Boundary at 64 w
Tectonics, 2008Co-Authors: S A Clark, A Levander, M B Magnani, C A ZeltAbstract:[1] Prior studies of the Caribbean–South American Plate Boundary have suffered from poor constraint on the structure of the crust and uppermost mantle. We use a recent wide-angle velocity model from the Broadband Ocean-Land Investigation of Venezuela and the Antilles arc Region project to constrain new seismic reflection data and previously published line drawing interpretations of the Caribbean–South American Plate Boundary at 64°W. Though commonly characterized as obliquely convergent, we determine that convergence is negligible in our study area. Previous estimates of Miocene to present north-south shortening onshore eastern Venezuela have commonly been 115 km or higher, but we constrain shortening to ∼35 km onshore, with an additional ∼30 km offshore. With such minor convergence, we conclude that uplift and basin subsidence in eastern Venezuela does not derive from typical collisional orogeny. Instead, the largely vertical tectonics likely result from mantle dynamics associated with an eastward propagating, near-vertical tear in the lithosphere along the former passive margin.
M B Magnani - One of the best experts on this subject based on the ideXlab platform.
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the caribbean south american Plate Boundary at 65 w results from wide angle seismic data
Journal of Geophysical Research, 2010Co-Authors: Maximiliano Bezada, C A Zelt, M B Magnani, Michael Schmitz, A LevanderAbstract:[1] We present the results of the analysis of new wide-angle seismic data across the Caribbean–South American Plate Boundary in eastern Venezuela at about 65°W. The ∼500 km long profile crosses the Boundary in one of the few regions dominated by extensional structures, as most of the southeastern Caribbean margin is characterized by the presence of fold and thrust belts. A combination of first-arrival traveltime inversion and simultaneous inversion of PmP and Pn arrivals was used to develop a P wave velocity model of the crust and the uppermost mantle. At the main strike-slip fault system, we image the Cariaco Trough, a major pull-apart basin along the Plate Boundary. The crust under the Southern Caribbean Deformed Belt exhibits a thickness of ∼15 km, suggesting that the Caribbean Large Igneous Province extends to this part of the Caribbean Plate. The velocity structures of basement highs and offshore sedimentary basins imaged by the profile are comparable to those of features found in other parts of the margin, suggesting similarities in their tectonic history. We do not image an abrupt change in Moho depth or velocity structure across the main strike-slip system, as has been observed elsewhere along the margin. It is possible that a terrane of Caribbean island arc origin was accreted to South America at this site and was subsequently bisected by the strike-slip fault system. The crust under the continental portion of the profile is thinner than observed elsewhere along the margin, possibly as a result of thinning during Jurassic rifting.
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negligible convergence and lithospheric tearing along the caribbean south american Plate Boundary at 64 w
Tectonics, 2008Co-Authors: S A Clark, A Levander, M B Magnani, C A ZeltAbstract:[1] Prior studies of the Caribbean–South American Plate Boundary have suffered from poor constraint on the structure of the crust and uppermost mantle. We use a recent wide-angle velocity model from the Broadband Ocean-Land Investigation of Venezuela and the Antilles arc Region project to constrain new seismic reflection data and previously published line drawing interpretations of the Caribbean–South American Plate Boundary at 64°W. Though commonly characterized as obliquely convergent, we determine that convergence is negligible in our study area. Previous estimates of Miocene to present north-south shortening onshore eastern Venezuela have commonly been 115 km or higher, but we constrain shortening to ∼35 km onshore, with an additional ∼30 km offshore. With such minor convergence, we conclude that uplift and basin subsidence in eastern Venezuela does not derive from typical collisional orogeny. Instead, the largely vertical tectonics likely result from mantle dynamics associated with an eastward propagating, near-vertical tear in the lithosphere along the former passive margin.
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characterizing the caribbean south american Plate Boundary at 64 w using wide angle seismic data
Journal of Geophysical Research, 2008Co-Authors: C A Zelt, M B Magnani, Stephen Clark, A LevanderAbstract:[1] We present wide-angle velocity modeling results from profile 64°W of the Broadband Ocean-Land Investigation of Venezuela and the Antilles arc Region (BOLIVAR) project. Line 64W is a 460-km-long, approximately north-south, onshore-offshore reflection/refraction transect located approximately at 64°W longitude. The profile extends across the transform Plate Boundary between the southeastern Caribbean (CAR) and South American (SA) Plates. East of the profile the Plate Boundary bends to the north, and SA subducts beneath CAR. We utilize first-arrival tomography to resolve a smooth velocity field for the sediments and upper/middle crust and then use a layered approach to resolve a sharp velocity contrast for the Moho, simultaneously inverting refracted Pn and reflected PmP arrivals. We image crustal and upper mantle structure across the Plate Boundary zone. We interpret that the strike-slip system that accommodates relative motion between CAR and SA extends near vertically through the entire crust and offsets the Moho. We see no evidence supporting a major component of convergence, and rather than a wide Boundary zone of overlapping lithospheric Plates, we interpret the Plate Boundary to be confined to the 33-km-wide, near-vertical strike-slip system. Previously interpreted thrust faults flanking the strike-slip system appear to be confined to the upper/middle crust and may be related to the detachment of subducting South American lithosphere at the southern terminus of the Lesser Antilles subduction zone east of 64°W.
