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C Demets - One of the best experts on this subject based on the ideXlab platform.
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crustal velocity field of mexico from continuous gps measurements 1993 to june 2001 implications for the neotectonics of mexico
Journal of Geophysical Research, 2003Co-Authors: B Marquezazua, C DemetsAbstract:[1] We combine velocities for 14 continuous GPS stations spanning Mexico and 173 additional continuous GPS sites on the North American and Pacific Plates to study the large-scale deformation of Mexico. The new station velocities, which are derived from more than 6000 days of previously unused GPS data, provide the first ever view of the crustal velocity field of Mexico. Key results are as follows: (1) Areas north of the Mexican Volcanic Belt, not including Baja California, move with the North American Plate Interior within the 1–2 mm yr−1 station velocity uncertainties. Station velocities for the Mexican Basin and Range are consistent with no present-day extension and yield an upper 95% limit of 1–3 mm yr−1 for any regional extension. (2) South of the Mexican Volcanic Belt, five of the six sites move significantly relative to the North American Plate. All sites in the Yucatan Peninsula move toward the east at 3–4 mm yr−1, possibly defining an independent Yucatan block. (3) Site velocities are consistent with limits of 0–4 mm yr−1 for present slip across the Mexican Volcanic Belt. (4) Tampico, on the gulf coast, exhibits eastward motion consistent with gravity sliding known to occur in the adjacent Mexican Ridges fold belt. (5) Southeastward motion of La Paz relative to the Pacific Plate is consistent with the hypothesis that the Baja Peninsula is not fully attached to the Pacific Plate. (6) Residual velocities for 160 North American Plate GPS stations outside of Mexico exhibit no coherent regional patterns indicative of internal Plate deformation.
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GPS geodetic constraints on Caribbean-North America Plate motion
Geophysical Research Letters, 2000Co-Authors: C Demets, Timothy H Dixon, Pamela E Jansma, Roger Bilham, Glen S. Mattioli, Fred Farina, Eric Calais, Paul MannAbstract:We describe a model for Caribbean Plate motion based on GPS velocities of four sites in the Plate Interior and two azimuths of the Swan Islands transform fault. The data are well fit by a single angular velocity, with average misfits approximately equal to the 1.5–3.0 mm yr−1 velocity uncertainties. The new model predicts Caribbean-North America motion ∼65% faster than predicted by NUVEL-1A, averaging 18–20±3 mm yr−1 (2σ) at various locations along the Plate boundary. The data are best fit by a rotation pole that predicts obliquely convergent motion along the Plate boundary east of Cuba, but are fit poorly by a suite of previously published models that predict strike-slip motion in this region. The data suggest an approximate upper bound of 4–6 mm yr−1 for internal deformation of the Caribbean Plate, although rigorous estimates await more precise and additional velocities from sites in the Plate Interior.
Timothy H Dixon - One of the best experts on this subject based on the ideXlab platform.
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GPS geodetic constraints on Caribbean-North America Plate motion
Geophysical Research Letters, 2000Co-Authors: C Demets, Timothy H Dixon, Pamela E Jansma, Roger Bilham, Glen S. Mattioli, Fred Farina, Eric Calais, Paul MannAbstract:We describe a model for Caribbean Plate motion based on GPS velocities of four sites in the Plate Interior and two azimuths of the Swan Islands transform fault. The data are well fit by a single angular velocity, with average misfits approximately equal to the 1.5–3.0 mm yr−1 velocity uncertainties. The new model predicts Caribbean-North America motion ∼65% faster than predicted by NUVEL-1A, averaging 18–20±3 mm yr−1 (2σ) at various locations along the Plate boundary. The data are best fit by a rotation pole that predicts obliquely convergent motion along the Plate boundary east of Cuba, but are fit poorly by a suite of previously published models that predict strike-slip motion in this region. The data suggest an approximate upper bound of 4–6 mm yr−1 for internal deformation of the Caribbean Plate, although rigorous estimates await more precise and additional velocities from sites in the Plate Interior.
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How rigid is the stable Interior of the North American Plate
Geophysical Research Letters, 1996Co-Authors: Timothy H Dixon, Seth SteinAbstract:We analyze data from eight permanent GPS stations broadly distributed through the Interior of the North American Plate, and use the resulting velocities to estimate an Euler vector describing motion of “stable” North America as a single rigid Plate. The site velocities fit the single Plate model with a mean residual of 1.3 mm/yr. The residuals do not appear to reflect post-glacial rebound, and tests for differential motion between eastern and western North America at the New Madrid seismic zone show no resolvable motion within uncertainties. The residuals likely reflect observational error, and thus our estimate of the stability of the Plate Interior is likely an upper bound.
Barbara Cavalazzi - One of the best experts on this subject based on the ideXlab platform.
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Tectonic link between the Neoproterozoic dextral shear fabrics and Cenozoic extension structures of the Mekelle basin, Northern Ethiopia
International Journal of Earth Sciences, 2020Co-Authors: Miruts Hagos, Tesfamichael Gebreyohannes, Kassa Amare, Abdelwasie Hussien, Gebremedhin Berhane, Kristine Walraevens, Christian Koeberl, Benjamin Wyk De Vries, Barbara CavalazziAbstract:The Mekelle basin (area ~ 5500 km^2) is located at the immediate western margin of the Afar Depression, which has a history of collision, subsidence, uplift, magmatism and now rifting. The evolution of such small to medium size basins as the Mekelle in a complicated geodynamic set-up is a subject of debate, because several different mechanisms of basin formation could apply. To address the possible basin evolution scenarios, we combine structural and dynamic analyses of northern Ethiopia, with strong emphasis on the basin and basin bounding basement rocks. The northern basin bounding block is uplifted by about 1500 m compared with the western and southwestern basin-bounding blocks. In the basin, superposition of large-scale orthogonal brittle shear fabrics and the development of young, parallel to subparallel extensional fractures and domino faulting have produced a total of ~ 2200 m vertical displacement. These observations, coupled with the absence of gradual roll-down of the internal basin (i.e., absence of bending/folding of an elastic beam supported at both ends), imply that Mekelle basin is not an IntraCONtinental Sags (ICONS) or Plate Interior basin, as previously described, but is instead a multi-tectonic triggered basin. Integrated satellite images using ground-controlled measurements and deep borehole data were used to decipher the entire evolution of the basin starting from the late-collisional deformation through the regional up-doming to the sills/dikes injection and basin formation.
Seth Stein - One of the best experts on this subject based on the ideXlab platform.
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How rigid is the stable Interior of the North American Plate
Geophysical Research Letters, 1996Co-Authors: Timothy H Dixon, Seth SteinAbstract:We analyze data from eight permanent GPS stations broadly distributed through the Interior of the North American Plate, and use the resulting velocities to estimate an Euler vector describing motion of “stable” North America as a single rigid Plate. The site velocities fit the single Plate model with a mean residual of 1.3 mm/yr. The residuals do not appear to reflect post-glacial rebound, and tests for differential motion between eastern and western North America at the New Madrid seismic zone show no resolvable motion within uncertainties. The residuals likely reflect observational error, and thus our estimate of the stability of the Plate Interior is likely an upper bound.
Ben A Van Der Pluijm - One of the best experts on this subject based on the ideXlab platform.
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sevier laramide deformation of the continental Interior from calcite twinning analysis west central north america
Tectonophysics, 1999Co-Authors: John P Craddock, Ben A Van Der PluijmAbstract:Abstract Paleozoic–Mesozoic carbonates that cover cratonic western North America contain a regional layer-parallel shortening (LPS) fabric that is preserved by mechanically twinned calcite. Shortening directions are generally parallel to the Sevier thrust-transport direction (E–W) in carbonates of the Idaho–Wyoming portion of the thrust belt and within carbonates as far as 2000 km into the Plate Interior. The inferred calcite twinning differential stress magnitudes generally decrease across the thrust belt, and decrease exponentially away from the orogenic front into the craton. Synorogenic calcite cements and veins preserve a distinct twinning deformation history: in the thrust belt, twinning strains commonly record local, out-of-transport piggyback strain events with high differential stresses (