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Robert Dirk Van Der Hilst - One of the best experts on this subject based on the ideXlab platform.
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constraints on residual topography and crustal properties in the western united states from virtual deep seismic sounding
Journal of Geophysical Research, 2016Co-Authors: Chunquan Yu, Wangping Chen, Robert Dirk Van Der HilstAbstract:We use virtual deep seismic sounding (VDSS) and data from ~1,000 broadband seismic stations to provide high-resolution estimates of crustal structure in the western Cordillera of the United States (US). The most robust result is the geographic distribution of residual topography (that is, the difference between observed elevation and that expected from crustal buoyancy alone) and, by implication, thermal or petrologic anomalies in the mantle. Overall, residual topography of the western US Cordillera varies considerably; with contrasts of up to about 3 km across distances of 200 km or less. High residual topography, indicating large mantle effects, is evident along the periphery of the Colorado Plateau and the surroundings of the Great Basin. In contrast, the central Colorado Plateau and the Wyoming Basin show low residual topography, close to what is expected of a geologically stable lithosphere. Overall, in regions to the east of the Wasatch Hinge Line (the eastern limit of significant extension in the North American cratonic basement) patterns of high residual topography and anomalies of low seismic wave-speeds in the upper mantle are similar, suggestive of a common, thermal origin. In contrast, such a similarity is absent in regions to the west of the Hinge Line, suggesting substantial effects of petrological heterogeneities in the mantle. Finally, joint analyses of VDSS and conventional receiver functions reveal a wide range of crustal P-wave speeds, locally as high as 6.7 km/s, perhaps indicating magmatic modification of the crust.
Wangping Chen - One of the best experts on this subject based on the ideXlab platform.
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constraints on residual topography and crustal properties in the western united states from virtual deep seismic sounding
Journal of Geophysical Research, 2016Co-Authors: Chunquan Yu, Wangping Chen, Robert Dirk Van Der HilstAbstract:We use virtual deep seismic sounding (VDSS) and data from ~1,000 broadband seismic stations to provide high-resolution estimates of crustal structure in the western Cordillera of the United States (US). The most robust result is the geographic distribution of residual topography (that is, the difference between observed elevation and that expected from crustal buoyancy alone) and, by implication, thermal or petrologic anomalies in the mantle. Overall, residual topography of the western US Cordillera varies considerably; with contrasts of up to about 3 km across distances of 200 km or less. High residual topography, indicating large mantle effects, is evident along the periphery of the Colorado Plateau and the surroundings of the Great Basin. In contrast, the central Colorado Plateau and the Wyoming Basin show low residual topography, close to what is expected of a geologically stable lithosphere. Overall, in regions to the east of the Wasatch Hinge Line (the eastern limit of significant extension in the North American cratonic basement) patterns of high residual topography and anomalies of low seismic wave-speeds in the upper mantle are similar, suggestive of a common, thermal origin. In contrast, such a similarity is absent in regions to the west of the Hinge Line, suggesting substantial effects of petrological heterogeneities in the mantle. Finally, joint analyses of VDSS and conventional receiver functions reveal a wide range of crustal P-wave speeds, locally as high as 6.7 km/s, perhaps indicating magmatic modification of the crust.
Eric Rignot - One of the best experts on this subject based on the ideXlab platform.
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Hinge-Line Migration of Petermann Gletscher, North Greenland, Detected Using Satellite Radar Interferometry
Journal of Glaciology, 1998Co-Authors: Eric RignotAbstract:The synthetic-aperture radar-interferometry technique is used to detect the migration of the limit of tidal flexing, or Hinge Line, of the floating ice tongue of Petermann Gletscher, a major outlet glacier of north Greenland. The Hinge Line is detected automatically from differential interferograms using a model-fitting technique based on an elastic-beam theory. The statistical noise of the model fit is less than 3 mm, and the Hinge Line is mapped with a precision of 30 m. Following automatic registration of multidate image data to a precision of 5 m, Hinge-Line migration is subsequently detected with a precision of 40 m in the horizontal plane across the glacier width. The results show that the Hinge Line of Petermann Gletscher migrates back and forth with tide by ± 70 m, in excellent agreement with the migration calculated from ocean tides predicted by a tidal model combined with the glacier surface and basal slope measured by an ice-sounding radar. Superimposed on the short-term Hinge-Line migration due to tide, we detect a Hinge-Line retreat of 270 m in 3.87 years which varies across the glacier width by ± 120 m. The retreat suggests glacier thinning at a rate of 78 ± 35 cm ice a-1. Coincidentally, an analysis of ice-volume fluxes indicates that the Hinge-Line ice flux of Petermann Gletscher exceeds its balance flux by 0.88±1 km3 ice a-1, which in turn implies glacier thinning at 83 ± 95 cm ice a-1 in the glacier lower reaches. Both methods therefore suggest that Petermann Gletscher is currently losing mass to the ocean.
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Radar Interferometry Detection of Hinge Line Migration on Rutford Ice Stream and Carlson Inlet, Antarctica
Annals of Glaciology, 1998Co-Authors: Eric RignotAbstract:Satellite synthetic-aperture radar (SAR) Interferometry is employed to map the Hinge Line, or limit of tidal flexing, of Rutford Ice Stream and Carlson Inlet, Antarctica, and detect its migration between 1992 and 1996. The Hinge Line is mapped using a model fit from an elastic beam theory.
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tidal motion ice velocity and melt rate of petermann gletscher greenland measured from radar interferometry
Journal of Glaciology, 1996Co-Authors: Eric RignotAbstract:Over a floating glacier ice tongue or an ice shelf, the glacier motion measured by a single, repeat-pass, radar interferogram is difficult to analyze, because the long-term, steady motion of the ice is intermixed with its cyclic, downward motion induced by tidal forcing. Multiple interferograms and a quadruple-difference technique are necessary to separate the tidal signal from the long-term, steady motion of the ice. An example of application of this technique is given here using ERS-1 radar images of Petermann Gletscher, a major outlet glacier of northern Greenland. Tidal displacements are measured with <5 mm statistical noise. The long-term ice velocity is measured with a precision of 1 m a-1. The inferred tidal displacements agree well with model predictions from a fixed elastic beam with an elastic damping factor of 0.47 ± 0.01 km-1. The Hinge Line is mapped with a precision of 20-80 m. Combining the interferometric ice velocities with ice thickness data, the glacier ice discharge is calculated at and below the Hinge Line. At the Hinge Line, the ice flux is 12.1 ± 1 km3 a-1. At the ice front, calf-ice production is only 0.59 km3 a-1, meaning that 95% of the ice that crosses the grounding Line melts before it reaches the calving front. Assuming steady-state conditions, the melt rate of the glacier tongue averages 12 ± 1 m a-1, with peak values exceeding 20 m a-1 near the Hinge Line. This high melt rate cannot be accommodated by surface ablation alone (only about 2-3 m a-1) and is attributed to pronounced basal melting of the ice tongue. Basal melting, often assumed to be negligible in Greenland, is the dominant process of mass release from the floating section of Petermann Gletscher.
Chunquan Yu - One of the best experts on this subject based on the ideXlab platform.
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constraints on residual topography and crustal properties in the western united states from virtual deep seismic sounding
Journal of Geophysical Research, 2016Co-Authors: Chunquan Yu, Wangping Chen, Robert Dirk Van Der HilstAbstract:We use virtual deep seismic sounding (VDSS) and data from ~1,000 broadband seismic stations to provide high-resolution estimates of crustal structure in the western Cordillera of the United States (US). The most robust result is the geographic distribution of residual topography (that is, the difference between observed elevation and that expected from crustal buoyancy alone) and, by implication, thermal or petrologic anomalies in the mantle. Overall, residual topography of the western US Cordillera varies considerably; with contrasts of up to about 3 km across distances of 200 km or less. High residual topography, indicating large mantle effects, is evident along the periphery of the Colorado Plateau and the surroundings of the Great Basin. In contrast, the central Colorado Plateau and the Wyoming Basin show low residual topography, close to what is expected of a geologically stable lithosphere. Overall, in regions to the east of the Wasatch Hinge Line (the eastern limit of significant extension in the North American cratonic basement) patterns of high residual topography and anomalies of low seismic wave-speeds in the upper mantle are similar, suggestive of a common, thermal origin. In contrast, such a similarity is absent in regions to the west of the Hinge Line, suggesting substantial effects of petrological heterogeneities in the mantle. Finally, joint analyses of VDSS and conventional receiver functions reveal a wide range of crustal P-wave speeds, locally as high as 6.7 km/s, perhaps indicating magmatic modification of the crust.
Fernando Calamita - One of the best experts on this subject based on the ideXlab platform.
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distribution of joints in the Hinge Line culmination of foreland verging overturned anticLines an example from the montagna dei fiori structure in the central apennines of italym francioni et al distribution of joints in overturned anticLines
Geological Magazine, 2019Co-Authors: Mirko Francioni, Paolo Pace, Milena Vitulli, Nicola Sciarra, Fernando CalamitaAbstract:The distribution of joints, veins and shear fractures in the Montagna dei Fiori overturned anticLine is here reported. Two joint sets, longitudinal and transverse to the NNW–SSE anticLine axial trend, and a conjugate system of shear fractures, are recognized. The transverse and longitudinal joint sets have a pre-folding development likely related to the foreland/foredeep flexure. The transverse joints were reopened during layer-parallel shortening along with the development of the shear fractures. Then, during syn-folding outer-arc extension and Hinge-Line culmination fold-axial parallel extension, both the longitudinal and transverse joints were enhanced and reactivated, respectively.