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Lucy M. Flesch - One of the best experts on this subject based on the ideXlab platform.
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kinematics and dynamics of the pamir central asia quantifying surface deformation and force balance in an intracontinental subduction zone
Journal of Geophysical Research, 2017Co-Authors: Lucy M. Flesch, Rebecca BendickAbstract:Kinematic and dynamic models quantify deformation and force balance in the Pamir, a region undergoing the rare and poorly understood process of intracontinental subduction. We constrain a detailed kinematic model with 506 recent GPS velocities and Quaternary fault slip rates and show that the Pamir is organized like the Himalaya and Tibet, with regions of 1) localized strain rate ≥100e-9/yr along the Pamir Frontal Thrust System (the subduction interface), similar to the Himalaya, and 2) distributed north-south compression and east-west extension, similar to Tibet. Through standard thin viscous sheet methods we demonstrate that the lithospheric force balance in the Pamir is a combination of stresses caused by Gravitational Potential Energy and India-Eurasia convergence accommodated at a subduction interface, in this case the Pamir Frontal Thrust System. We find that strain rate and deviatoric stress patterns near the Pamir Frontal Thrust System are characteristic of a mature subduction zone, despite its initiation in continental lithosphere. Although the Pamir and Tibet are kinematically and dynamically similar, the Pamir is stiffer overall than Tibet, perhaps due to the presence of the highly arcuate, geometrically stiffened continental slab at depth.
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Contribution of Gravitational Potential Energy differences to the global stress field
Geophysical Journal International, 2009Co-Authors: A. Ghosh, William E. Holt, Lucy M. FleschAbstract:SUMMARY Modelling the lithospheric stress field has proved to be an efficient means of determining the role of lithospheric versus sublithospheric buoyancies and also of constraining the driving forces behind plate tectonics. Both these sources of buoyancies are important in generating the lithospheric stress field. However, these sources and the contribution that they make are dependent on a number of variables, such as the role of lateral strength variation in the lithosphere, the reference level for computing the Gravitational Potential Energy per unit area (GPE) of the lithosphere, and even the definition of deviatoric stress. For the mantle contribution, much depends on the mantle convection model, including the role of lateral and radial viscosity variations, the spatial distribution of density buoyancies, and the resolution of the convection model. GPE differences are influenced by both lithosphere density buoyancies and by radial basal tractions that produce dynamic topography. The global lithospheric stress field can thus be divided into (1) stresses associated with GPE differences (including the contribution from radial basal tractions) and (2) stresses associated with the contribution of horizontal basal tractions. In this paper, we investigate only the contribution of GPE differences, both with and without the inferred contribution of radial basal tractions. We use the Crust 2.0 model to compute GPE values and show that these GPE differences are not sufficient alone to match all the directions and relative magnitudes of principal strain rate axes, as inferred from the comparison of our depth integrated deviatoric stress tensor field with the velocity gradient tensor field within the Earth's plate boundary zones. We argue that GPE differences calibrate the absolute magnitudes of depth integrated deviatoric stresses within the lithosphere; shortcomings of this contribution in matching the stress indicators within the plate boundary zones can be corrected by considering the contribution from horizontal tractions associated with density buoyancy driven mantle convection. Deviatoric stress magnitudes arising from GPE differences are in the range of 1–4 TN m−1, a part of which is contributed by dynamic topography. The EGM96 geoid data set is also used as a rough proxy for GPE values in the lithosphere. However, GPE differences from the geoid fail to yield depth integrated deviatoric stresses that can provide a good match to the deformation indicators. GPE values inferred from the geoid have significant shortcomings when used on a global scale due to the role of dynamically support of topography. Another important factor in estimating the depth integrated deviatoric stresses is the use of the correct level of reference in calculating GPE. We also elucidate the importance of understanding the reference pressure for calculating deviatoric stress and show that overestimates of deviatoric stress may result from either simplified 2-D approximations of the thin sheet equations or the assumption that the mean stress is equal to the vertical stress.
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the dynamics of western north america stress magnitudes and the relative role of Gravitational Potential Energy plate interaction at the boundary and basal tractions
Geophysical Journal International, 2007Co-Authors: William E. Holt, Lucy M. Flesch, John A Haines, L Wen, Bingming ShentuAbstract:SUMMARY We investigate the forces involved in driving long-term large-scale continental deformation in western North America, and quantify the vertically averaged deviatoric stress field arising from internal buoyancy forces and the accommodation of relative plate motions. In addition, we investigate the ability of regional models to resolve the level of tractions acting at the base of the lithosphere. We directly solve force-balance equations for vertically averaged deviatoric stresses associated with differences in values of 1/(lithospheric thickness) times the Gravitational Potential Energy per unit area (GPE). The GPE values are inferred using both the ETOPO5 topographic data set and the CRUST2.0 crustal thickness model. Deviatoric stresses associated with basal tractions are calculated globally, with inputs determined from an isoviscous upper mantle (η = 10 21 Pa s) 3-D large-scale convection model in which mantle density variations were inferred from tomographic data and the history of subduction. In a 211parameter iterative inversion we then solve for a stress field boundary condition by fitting stress field indicators (i.e. the directions and relative magnitudes of the principal axes of kinematic strain rates). Magnitudes of the total vertically averaged deviatoric stress field (sum of GPE solution with the boundary condition solution) range from 5 to 10 MPa within a 100-km thick lithosphere. These magnitudes are calibrated by the GPE differences, along with the spatial variation in deformation style. There is a trade-off between the scaling of the basal traction deviatoric stress field and the boundary condition solution. However, the combined boundary conditions plus basal traction solution is robust (in both magnitude and style), and when added to the contribution from GPE differences provides a global minimum of misfit between the total deviatoric stress solution and the stress field indicators. GPE variations account for ∼50 per cent of the deviatoric stress magnitudes driving deformation, while boundary condition stresses account for the remaining ∼50 per cent of deviatoric stress magnitude. By comparing possible end-member strength profiles with our vertically averaged deviatoric stresses we infer that the bulk of the strength within the lithosphere in western North America lies within the brittle seismogenic layer.
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dynamics of the india eurasia collision zone
Journal of Geophysical Research, 2001Co-Authors: Lucy M. Flesch, John A Haines, William E. HoltAbstract:We present simple new dynamic calculations of a vertically averaged deviatoric stress field (over a depth average of 100 km) for Asia from geodetic, geologic, topographic, and seismic data. A first estimate of the minimum absolute magnitudes and directions of vertically averaged deviatoric stress is obtained by solving force balance equations for deviatoric stresses associated with Gravitational Potential Energy differences within the lithosphere plus a first-order contribution of deviatoric stresses associated with stress boundary conditions. This initial estimate of the vertically averaged deviatoric stress field is obtained independent of assumptions about the rheology of the lithosphere. Absolute magnitudes of vertically averaged deviatoric stresses vary between 5 and 40 MPa. Assuming bulk viscous behavior for the lithosphere, the magnitudes of deviatoric stresses, together with the magnitudes of strain rates inferred from Quaternary fault slip rate and GPS data, yield vertically averaged effective viscosities for Tibet of 0.5–5×1022 Pa s, compared with 1–2.5×1023 Pa s in more rigid areas elsewhere in the region. A forward modeling method that solves force balance equations using velocity boundary conditions allows us to refine our estimates of the vertically averaged effective viscosity distribution and deviatoric stress field. The total vertically averaged deviatoric stress and effective viscosity field are consistent with a weak lower crust in Tibet; they are consistent with some eastward motion of Tibet and south China lithosphere relative to Eurasia; and they confirm that Gravitational Potential Energy differences have a profound effect on the spatially varying style and magnitude of strain rate around the Tibetan Plateau. Our results for the vertically averaged deviatoric stress argue for a large portion of the strength of the lithosphere to reside within the seismogenic upper crust to get deviatoric stress magnitudes there to be as high as 100–300 MPa (in accord with laboratory and theoretical friction experiments indicating that stress drops in earthquakes are small fractions of the total deviatoric stress).
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dynamics of the pacific north american plate boundary in the western united states
Science, 2000Co-Authors: Lucy M. Flesch, William E. Holt, John A Haines, Bingming ShentuAbstract:The vertically averaged deviatoric stress tensor field within the western United States was determined with topographic data, geoid data, recent global positioning system observations, and strain rate magnitudes and styles from Quaternary faults. Gravitational Potential Energy differences control the large fault-normal compression on the California coast. Deformation in the Basin and Range is driven, in part, by Gravitational Potential Energy differences, but extension directions there are modified by plate interaction stresses. The California shear zone has relatively low vertically averaged viscosity of about 1021 pascal·seconds, whereas the Basin and Range has a higher vertically averaged viscosity of 1022pascal·seconds.
William E. Holt - One of the best experts on this subject based on the ideXlab platform.
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Contribution of Gravitational Potential Energy differences to the global stress field
Geophysical Journal International, 2009Co-Authors: A. Ghosh, William E. Holt, Lucy M. FleschAbstract:SUMMARY Modelling the lithospheric stress field has proved to be an efficient means of determining the role of lithospheric versus sublithospheric buoyancies and also of constraining the driving forces behind plate tectonics. Both these sources of buoyancies are important in generating the lithospheric stress field. However, these sources and the contribution that they make are dependent on a number of variables, such as the role of lateral strength variation in the lithosphere, the reference level for computing the Gravitational Potential Energy per unit area (GPE) of the lithosphere, and even the definition of deviatoric stress. For the mantle contribution, much depends on the mantle convection model, including the role of lateral and radial viscosity variations, the spatial distribution of density buoyancies, and the resolution of the convection model. GPE differences are influenced by both lithosphere density buoyancies and by radial basal tractions that produce dynamic topography. The global lithospheric stress field can thus be divided into (1) stresses associated with GPE differences (including the contribution from radial basal tractions) and (2) stresses associated with the contribution of horizontal basal tractions. In this paper, we investigate only the contribution of GPE differences, both with and without the inferred contribution of radial basal tractions. We use the Crust 2.0 model to compute GPE values and show that these GPE differences are not sufficient alone to match all the directions and relative magnitudes of principal strain rate axes, as inferred from the comparison of our depth integrated deviatoric stress tensor field with the velocity gradient tensor field within the Earth's plate boundary zones. We argue that GPE differences calibrate the absolute magnitudes of depth integrated deviatoric stresses within the lithosphere; shortcomings of this contribution in matching the stress indicators within the plate boundary zones can be corrected by considering the contribution from horizontal tractions associated with density buoyancy driven mantle convection. Deviatoric stress magnitudes arising from GPE differences are in the range of 1–4 TN m−1, a part of which is contributed by dynamic topography. The EGM96 geoid data set is also used as a rough proxy for GPE values in the lithosphere. However, GPE differences from the geoid fail to yield depth integrated deviatoric stresses that can provide a good match to the deformation indicators. GPE values inferred from the geoid have significant shortcomings when used on a global scale due to the role of dynamically support of topography. Another important factor in estimating the depth integrated deviatoric stresses is the use of the correct level of reference in calculating GPE. We also elucidate the importance of understanding the reference pressure for calculating deviatoric stress and show that overestimates of deviatoric stress may result from either simplified 2-D approximations of the thin sheet equations or the assumption that the mean stress is equal to the vertical stress.
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the dynamics of western north america stress magnitudes and the relative role of Gravitational Potential Energy plate interaction at the boundary and basal tractions
Geophysical Journal International, 2007Co-Authors: William E. Holt, Lucy M. Flesch, John A Haines, L Wen, Bingming ShentuAbstract:SUMMARY We investigate the forces involved in driving long-term large-scale continental deformation in western North America, and quantify the vertically averaged deviatoric stress field arising from internal buoyancy forces and the accommodation of relative plate motions. In addition, we investigate the ability of regional models to resolve the level of tractions acting at the base of the lithosphere. We directly solve force-balance equations for vertically averaged deviatoric stresses associated with differences in values of 1/(lithospheric thickness) times the Gravitational Potential Energy per unit area (GPE). The GPE values are inferred using both the ETOPO5 topographic data set and the CRUST2.0 crustal thickness model. Deviatoric stresses associated with basal tractions are calculated globally, with inputs determined from an isoviscous upper mantle (η = 10 21 Pa s) 3-D large-scale convection model in which mantle density variations were inferred from tomographic data and the history of subduction. In a 211parameter iterative inversion we then solve for a stress field boundary condition by fitting stress field indicators (i.e. the directions and relative magnitudes of the principal axes of kinematic strain rates). Magnitudes of the total vertically averaged deviatoric stress field (sum of GPE solution with the boundary condition solution) range from 5 to 10 MPa within a 100-km thick lithosphere. These magnitudes are calibrated by the GPE differences, along with the spatial variation in deformation style. There is a trade-off between the scaling of the basal traction deviatoric stress field and the boundary condition solution. However, the combined boundary conditions plus basal traction solution is robust (in both magnitude and style), and when added to the contribution from GPE differences provides a global minimum of misfit between the total deviatoric stress solution and the stress field indicators. GPE variations account for ∼50 per cent of the deviatoric stress magnitudes driving deformation, while boundary condition stresses account for the remaining ∼50 per cent of deviatoric stress magnitude. By comparing possible end-member strength profiles with our vertically averaged deviatoric stresses we infer that the bulk of the strength within the lithosphere in western North America lies within the brittle seismogenic layer.
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Gravitational Potential Energy of the tibetan plateau and the forces driving the indian plate
Geology, 2006Co-Authors: A. Ghosh, William E. Holt, L M Flesch, John A HainesAbstract:We present a study of the vertically integrated deviatoric stress field for the Indian plate and the Tibetan Plateau associated with Gravitational Potential Energy (GPE) differences. Although the driving forces for the Indian plate have been attributed solely to the mid-oceanic ridges that surround the entire southern boundary of the plate, previous estimates of vertically integrated stress magnitudes of ~6–7 x 1012 N/m in Tibet far exceed those of ~3 x 1012 N/m associated with GPE at mid-oceanic ridges, calling for an additional force to satisfy the stress magnitudes in Tibet. We use the Crust 2.0 data set to infer Gravitational Potential Energy differences in the lithosphere. We then apply the thin sheet approach in order to obtain a global solution of vertically integrated deviatoric stresses associated only with GPE differences. Our results show large N-S extensional deviatoric stresses in Tibet that the ridge-push force fails to cancel. Our results calibrate the magnitude of the basal tractions, associated with density buoyancy driven mantle flow, that are applied at the base of the lithosphere in order to drive India into Tibet and cancel the N-S extensional stresses within Tibet. Moreover, our deviatoric stress field solution indicates that both the ridge-push influence (~1 x 1012 N/m) and the vertically integrated deviatoric stresses associated with GPE differences around the Tibetan Plateau (~3 x 1012 N/m) have previously been overestimated by a factor of two or more. These overestimates have resulted from either simplified two-dimensional approximations of the thin sheet equations, or from an assumption about the mean stress that is unlikely to be correct.
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toward understanding the history and mechanisms of martian faulting the contribution of Gravitational Potential Energy
Geophysical Research Letters, 2006Co-Authors: L L Dimitrova, William E. Holt, John A Haines, Richard A SchultzAbstract:[1] Current stress solutions for Mars match the long wavelength signal of present day topography and gravity but fail to match many surface faults, including the normal faults in northern Claritas Fossae north to Tantalus and Alba Fossae. A deviatoric stress field associated with horizontal gradients of Gravitational Potential Energy (GPE) provides an excellent fit, as measured by objective functions, to many of the normal faults in the western Martian hemisphere as well as wrinkle ridges circumferential to Tharsis; ∼70% of the faults have a misfit ≤ 0.1. The fit of faults to the GPE-derived stress field reflects the thermal state of the planet at the times of faulting, and suggests that at such times elastic thicknesses and membrane stresses were small, and topography was supported by buoyancy forces.
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dynamics of the india eurasia collision zone
Journal of Geophysical Research, 2001Co-Authors: Lucy M. Flesch, John A Haines, William E. HoltAbstract:We present simple new dynamic calculations of a vertically averaged deviatoric stress field (over a depth average of 100 km) for Asia from geodetic, geologic, topographic, and seismic data. A first estimate of the minimum absolute magnitudes and directions of vertically averaged deviatoric stress is obtained by solving force balance equations for deviatoric stresses associated with Gravitational Potential Energy differences within the lithosphere plus a first-order contribution of deviatoric stresses associated with stress boundary conditions. This initial estimate of the vertically averaged deviatoric stress field is obtained independent of assumptions about the rheology of the lithosphere. Absolute magnitudes of vertically averaged deviatoric stresses vary between 5 and 40 MPa. Assuming bulk viscous behavior for the lithosphere, the magnitudes of deviatoric stresses, together with the magnitudes of strain rates inferred from Quaternary fault slip rate and GPS data, yield vertically averaged effective viscosities for Tibet of 0.5–5×1022 Pa s, compared with 1–2.5×1023 Pa s in more rigid areas elsewhere in the region. A forward modeling method that solves force balance equations using velocity boundary conditions allows us to refine our estimates of the vertically averaged effective viscosity distribution and deviatoric stress field. The total vertically averaged deviatoric stress and effective viscosity field are consistent with a weak lower crust in Tibet; they are consistent with some eastward motion of Tibet and south China lithosphere relative to Eurasia; and they confirm that Gravitational Potential Energy differences have a profound effect on the spatially varying style and magnitude of strain rate around the Tibetan Plateau. Our results for the vertically averaged deviatoric stress argue for a large portion of the strength of the lithosphere to reside within the seismogenic upper crust to get deviatoric stress magnitudes there to be as high as 100–300 MPa (in accord with laboratory and theoretical friction experiments indicating that stress drops in earthquakes are small fractions of the total deviatoric stress).
John A Haines - One of the best experts on this subject based on the ideXlab platform.
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the dynamics of western north america stress magnitudes and the relative role of Gravitational Potential Energy plate interaction at the boundary and basal tractions
Geophysical Journal International, 2007Co-Authors: William E. Holt, Lucy M. Flesch, John A Haines, L Wen, Bingming ShentuAbstract:SUMMARY We investigate the forces involved in driving long-term large-scale continental deformation in western North America, and quantify the vertically averaged deviatoric stress field arising from internal buoyancy forces and the accommodation of relative plate motions. In addition, we investigate the ability of regional models to resolve the level of tractions acting at the base of the lithosphere. We directly solve force-balance equations for vertically averaged deviatoric stresses associated with differences in values of 1/(lithospheric thickness) times the Gravitational Potential Energy per unit area (GPE). The GPE values are inferred using both the ETOPO5 topographic data set and the CRUST2.0 crustal thickness model. Deviatoric stresses associated with basal tractions are calculated globally, with inputs determined from an isoviscous upper mantle (η = 10 21 Pa s) 3-D large-scale convection model in which mantle density variations were inferred from tomographic data and the history of subduction. In a 211parameter iterative inversion we then solve for a stress field boundary condition by fitting stress field indicators (i.e. the directions and relative magnitudes of the principal axes of kinematic strain rates). Magnitudes of the total vertically averaged deviatoric stress field (sum of GPE solution with the boundary condition solution) range from 5 to 10 MPa within a 100-km thick lithosphere. These magnitudes are calibrated by the GPE differences, along with the spatial variation in deformation style. There is a trade-off between the scaling of the basal traction deviatoric stress field and the boundary condition solution. However, the combined boundary conditions plus basal traction solution is robust (in both magnitude and style), and when added to the contribution from GPE differences provides a global minimum of misfit between the total deviatoric stress solution and the stress field indicators. GPE variations account for ∼50 per cent of the deviatoric stress magnitudes driving deformation, while boundary condition stresses account for the remaining ∼50 per cent of deviatoric stress magnitude. By comparing possible end-member strength profiles with our vertically averaged deviatoric stresses we infer that the bulk of the strength within the lithosphere in western North America lies within the brittle seismogenic layer.
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Gravitational Potential Energy of the tibetan plateau and the forces driving the indian plate
Geology, 2006Co-Authors: A. Ghosh, William E. Holt, L M Flesch, John A HainesAbstract:We present a study of the vertically integrated deviatoric stress field for the Indian plate and the Tibetan Plateau associated with Gravitational Potential Energy (GPE) differences. Although the driving forces for the Indian plate have been attributed solely to the mid-oceanic ridges that surround the entire southern boundary of the plate, previous estimates of vertically integrated stress magnitudes of ~6–7 x 1012 N/m in Tibet far exceed those of ~3 x 1012 N/m associated with GPE at mid-oceanic ridges, calling for an additional force to satisfy the stress magnitudes in Tibet. We use the Crust 2.0 data set to infer Gravitational Potential Energy differences in the lithosphere. We then apply the thin sheet approach in order to obtain a global solution of vertically integrated deviatoric stresses associated only with GPE differences. Our results show large N-S extensional deviatoric stresses in Tibet that the ridge-push force fails to cancel. Our results calibrate the magnitude of the basal tractions, associated with density buoyancy driven mantle flow, that are applied at the base of the lithosphere in order to drive India into Tibet and cancel the N-S extensional stresses within Tibet. Moreover, our deviatoric stress field solution indicates that both the ridge-push influence (~1 x 1012 N/m) and the vertically integrated deviatoric stresses associated with GPE differences around the Tibetan Plateau (~3 x 1012 N/m) have previously been overestimated by a factor of two or more. These overestimates have resulted from either simplified two-dimensional approximations of the thin sheet equations, or from an assumption about the mean stress that is unlikely to be correct.
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toward understanding the history and mechanisms of martian faulting the contribution of Gravitational Potential Energy
Geophysical Research Letters, 2006Co-Authors: L L Dimitrova, William E. Holt, John A Haines, Richard A SchultzAbstract:[1] Current stress solutions for Mars match the long wavelength signal of present day topography and gravity but fail to match many surface faults, including the normal faults in northern Claritas Fossae north to Tantalus and Alba Fossae. A deviatoric stress field associated with horizontal gradients of Gravitational Potential Energy (GPE) provides an excellent fit, as measured by objective functions, to many of the normal faults in the western Martian hemisphere as well as wrinkle ridges circumferential to Tharsis; ∼70% of the faults have a misfit ≤ 0.1. The fit of faults to the GPE-derived stress field reflects the thermal state of the planet at the times of faulting, and suggests that at such times elastic thicknesses and membrane stresses were small, and topography was supported by buoyancy forces.
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dynamics of the india eurasia collision zone
Journal of Geophysical Research, 2001Co-Authors: Lucy M. Flesch, John A Haines, William E. HoltAbstract:We present simple new dynamic calculations of a vertically averaged deviatoric stress field (over a depth average of 100 km) for Asia from geodetic, geologic, topographic, and seismic data. A first estimate of the minimum absolute magnitudes and directions of vertically averaged deviatoric stress is obtained by solving force balance equations for deviatoric stresses associated with Gravitational Potential Energy differences within the lithosphere plus a first-order contribution of deviatoric stresses associated with stress boundary conditions. This initial estimate of the vertically averaged deviatoric stress field is obtained independent of assumptions about the rheology of the lithosphere. Absolute magnitudes of vertically averaged deviatoric stresses vary between 5 and 40 MPa. Assuming bulk viscous behavior for the lithosphere, the magnitudes of deviatoric stresses, together with the magnitudes of strain rates inferred from Quaternary fault slip rate and GPS data, yield vertically averaged effective viscosities for Tibet of 0.5–5×1022 Pa s, compared with 1–2.5×1023 Pa s in more rigid areas elsewhere in the region. A forward modeling method that solves force balance equations using velocity boundary conditions allows us to refine our estimates of the vertically averaged effective viscosity distribution and deviatoric stress field. The total vertically averaged deviatoric stress and effective viscosity field are consistent with a weak lower crust in Tibet; they are consistent with some eastward motion of Tibet and south China lithosphere relative to Eurasia; and they confirm that Gravitational Potential Energy differences have a profound effect on the spatially varying style and magnitude of strain rate around the Tibetan Plateau. Our results for the vertically averaged deviatoric stress argue for a large portion of the strength of the lithosphere to reside within the seismogenic upper crust to get deviatoric stress magnitudes there to be as high as 100–300 MPa (in accord with laboratory and theoretical friction experiments indicating that stress drops in earthquakes are small fractions of the total deviatoric stress).
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dynamics of the pacific north american plate boundary in the western united states
Science, 2000Co-Authors: Lucy M. Flesch, William E. Holt, John A Haines, Bingming ShentuAbstract:The vertically averaged deviatoric stress tensor field within the western United States was determined with topographic data, geoid data, recent global positioning system observations, and strain rate magnitudes and styles from Quaternary faults. Gravitational Potential Energy differences control the large fault-normal compression on the California coast. Deformation in the Basin and Range is driven, in part, by Gravitational Potential Energy differences, but extension directions there are modified by plate interaction stresses. The California shear zone has relatively low vertically averaged viscosity of about 1021 pascal·seconds, whereas the Basin and Range has a higher vertically averaged viscosity of 1022pascal·seconds.
Shu Kun Hsu - One of the best experts on this subject based on the ideXlab platform.
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earthquake induced Gravitational Potential Energy change in the active taiwan orogenic belt
Geophysical Journal International, 2005Co-Authors: Shu Kun HsuAbstract:SUMMARY The Philippine Sea Plate is converging against the Eurasian Plate near Taiwan at a velocity of 7‐8 cm yr −1 ; this has caused the Taiwan orogenesis and induced abundant earthquakes. In this study we examine the corresponding change of Gravitational Potential Energy (�GPE) using 757 earthquakes from the earthquake catalogue of the Broadband Array in Taiwan for Seismology (BATS) from 1995 July to 2003 December. Our results show that the variation of
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change of crustal Gravitational Potential Energy in the taiwan orogen by the chi chi earthquake sequence
Earth and Planetary Science Letters, 2004Co-Authors: Shu Kun HsuAbstract:Abstract The active convergence between the northwest corner of the Philippine Sea Plate and the southeast margin of the Eurasian Plate has given rise to the Taiwan mountain-building and produced numerous earthquakes. Among the earthquakes, the 1999 Chi-Chi earthquake is the largest one recorded in the century. In this study, we examine the crustal Gravitational Potential Energy (GPE) change in the Taiwan orogen caused by the Chi-Chi earthquake sequence, which was catalogued by the regional broadband seismometer array for a whole year. As a result, we find that the crust was going up and down randomly during the earthquake sequence, but an overall cumulative gain of the crustal GPE, +1.82×10 16 J, was rapidly achieved in 1 month after the main shock. The crustal GPE was nearly still afterwards and reached +1.90×10 16 J in 1 year. Spatially, although the main surface faulting has occurred in western Taiwan, the crustal GPE gain is mainly distributed in central Taiwan at the area where the existing crustal GPE is high and the existing lithospheric GPE is relatively low. The crustal GPE loss by the Chi-Chi earthquake sequence can also be observed and is generally distributed at both sides of the crustal GPE gain area. The crustal GPE gain mainly found in central Taiwan corroborates that the uplift of the Taiwan orogen is principally taking place in central Taiwan, rather than in the more hazardous western Taiwan.
Zhang Y - One of the best experts on this subject based on the ideXlab platform.
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impact of vertical turbulence on ocean Gravitational Potential Energy and the tracer mixing process
Chinese Journal of Atmospheric Sciences, 2014Co-Authors: Zhang YAbstract:Using a WOA09(World Ocean Atlas 2009) data set of objectively analyzed in situ temperature and salinity, we calculate ocean Gravitational Potential Energy(GPE) and investigate the relationships between the mixing coefficient, buoyancy frequency, and GPE. On that basis, we further explore the impact of Energy conversion, caused by turbulent mixing, on turbulent parameterization. The research shows that ocean vertical turbulence is not only a kinetic Energy sink but also an important way of external Energy transformation to GPE. When the mixing coefficient is 0.1 cm2 s-1, GPE will increase 0.08 TW. Based on the results of other authors, we conclude that external Energy can induce a global average mixing coefficient of up to 12 cm2 s-1. In general, the more stable the stratification of the ocean and the larger the mixing coefficient, the higher the GPE increase. Parameterization can obtain more realistic results with careful treatment of turbulent kinetic Energy conversion to GPE.
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impact of vertical turbulence on ocean Gravitational Potential Energy and the tracer mixing process
Chinese Journal of Atmospheric Sciences, 2014Co-Authors: Zhang YAbstract:Using a WOA09(World Ocean Atlas 2009) data set of objectively analyzed in situ temperature and salinity, we calculate ocean Gravitational Potential Energy(GPE) and investigate the relationships between the mixing coefficient, buoyancy frequency, and GPE. On that basis, we further explore the impact of Energy conversion, caused by turbulent mixing, on turbulent parameterization. The research shows that ocean vertical turbulence is not only a kinetic Energy sink but also an important way of external Energy transformation to GPE. When the mixing coefficient is 0.1 cm2 s-1, GPE will increase 0.08 TW. Based on the results of other authors, we conclude that external Energy can induce a global average mixing coefficient of up to 12 cm2 s-1. In general, the more stable the stratification of the ocean and the larger the mixing coefficient, the higher the GPE increase. Parameterization can obtain more realistic results with careful treatment of turbulent kinetic Energy conversion to GPE.
