共查询到20条相似文献，搜索用时 31 毫秒
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Summary. The thickening plate theory proposed by Yoshii and Parker & Oldenburg for the oceanic lithosphere is extended to include the continental lithosphere. The theory is based on the assumption that the lithosphere—asthenosphere boundary is a solidus and that as a result solidification of the top of the asthenosphere is occurring. Observational data imply that the relationship between the plate thickness and basement age for the North American continent is y = 1.7 √ t + (50 ± 10), where y (km) is the plate thickness and t (Myr) is the basement age.
The theory is tested against changes with basement age of the observed surface heat-flow and seismic estimate of plate thickness. The following conclusions are inferred:
(1) The changes both of the observed heat flow and plate thickness with basement age are explained by this theory.
(2) The surface erosion and vertical distribution of radiogenic heat sources are important factors in controlling the thickening process of the continental lithosphere.
(3) The equality of the average surface heat-flow over the oceans and over the continents is a consequence of a faster release of latent heat at the lithosphere—asthenosphere boundary under the oceans, instead of a higher heat production in the continental crust. 相似文献
The theory is tested against changes with basement age of the observed surface heat-flow and seismic estimate of plate thickness. The following conclusions are inferred:
(1) The changes both of the observed heat flow and plate thickness with basement age are explained by this theory.
(2) The surface erosion and vertical distribution of radiogenic heat sources are important factors in controlling the thickening process of the continental lithosphere.
(3) The equality of the average surface heat-flow over the oceans and over the continents is a consequence of a faster release of latent heat at the lithosphere—asthenosphere boundary under the oceans, instead of a higher heat production in the continental crust. 相似文献
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Gabriele Marquart Harro Schmeling & Alexander Braun 《Geophysical Journal International》1999,138(3):655-666
Interpretation of satellite altimetry data as well as ship bathymetry data revealed strongly elongated anomalies roughly perpendicular to the mid-ocean ridges in the Indian and east Pacific oceans. A spectral analysis of gravity altimetry data along profiles parallel to the East Pacific Rise indicated wavelengths of about 150–180 km close to the ridge and about 250 km further away. A simple model of Rayleigh–Taylor instabilities developing at the base of the cooling lithosphere is discussed and applied to the data. By considering thermal diffusion and comparing Rayleigh–Taylor growth rates to the velocity of the thermal front in the cooling lithosphere, we are able to explain the observed anomalies by instabilities developing below the lithosphere in a layer with a viscosity of about 1019 Pa s above an asthenospheric layer with a viscosity reduction of 2–3 orders of magnitude. 相似文献
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Jean-Claude Mareschal 《Geophysical Journal International》1981,66(3):535-552
Summary. If one can measure the anomalous horizontal magnetic field associated with a (locally bounded) two-dimensional conductivity anomaly, the transfer function which results from correlating the vertical with the anomalous horizontal magnetic field directly indicates the depth to an equivalent line-current. A. numerical model can be used to illustrate this. If three-dimensional effects (including current channelling) produce the current anomaly, interpretation in terms of conductive structure would be less clear. It has been claimed (Babour & Mosnier etc.) that such three-dimensional effects are experimentally observed in the highly coherent transfer functions determined from differential geomagnetic sounding experiments. These effects are, specifically, the 'linear polarization' of the anomalous fields, and the invariance of the phase of the measured anomalous field across the anomaly. It is suggested in this present paper that both these effects can be explained in terms of simple local induction models.
If the embedded two-dimensional anomaly is sufficiently close to the Earth's surface, the transfer function (between the vertical and the total horizontal field) contains more information than is usually interpreted. With this in mind, the magnetovariational data collected by Rooney & Hutton in the Kenyan Rift is re-examined. 相似文献
If the embedded two-dimensional anomaly is sufficiently close to the Earth's surface, the transfer function (between the vertical and the total horizontal field) contains more information than is usually interpreted. With this in mind, the magnetovariational data collected by Rooney & Hutton in the Kenyan Rift is re-examined. 相似文献
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Summary. The flow of the mantle near subducted lithosphere applies a force (dynamic load) to the slab which has a normal component as well as a shear component. In addition, the greater density of the slab compared to the surrounding mantle results in a downward force (negative buoyancy) which also has a component normal to the slab. Because the slab is long compared to its thickness, the stresses in the slab due to the normal components of the loads are accurately estimated from the bending moment. We have used previous estimates of the loads to compute the bending moment in the slab as a function of distance down the slab. Our results indicate that the loads applied to the slab are large compared to its strength; bending moments due to normal loads will not be transmitted over the length of the slab. Instead, the slab will deflect so that the normal loads are balanced locally. 相似文献
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Deformation of subducted oceanic lithosphere 总被引：2，自引：0，他引：2
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Boris I. Birger 《Geophysical Journal International》2000,140(1):24-36
For flows associated with small strains, the rheology of rocks is described by the linear integral (having a memory) law, which reduces to the Andrade law in the case of constant stress. A continental lithosphere with such a rheology is overstable. Thermoconvective waves that propagate through the lithosphere with minimal attenuation have a period of about 200 Myr and a wavelength of the order of 400 km. An initial temperature point-concentrated perturbation in the lithosphere excites amplitude-modulated thermoconvective waves (wave packets). When the initial perturbation occurs in a finite area, thermoconvective waves propagate outwards from this area, and thermoconvective oscillations (standing waves) are established inside the area. Thermoconvective waves induce oscillations of the Earth' surface, accompanied by sedimentation and erosion, and can be considered as a mechanism for the distribution of sediments on continental cratons. 相似文献
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Eugene V. Artyushkov 《Geophysical Journal International》1984,76(1):173-178
Summary. It is known that flow in the mantle can produce preferred orientation in olivine crystals with seismic anisotropy as a consequence. Flow in the subcrustal lithosphere is unlikely because of the high viscosity. Lenses of high temperature and low-viscosity ( anomalous mantle ) are located under the crust in many tectonically active regions, and viscous flow can easily arise in such material resulting in seismic anisotropy. After cooling, such anomalous mantle acquires high viscosity and becomes incorporated into the lithospheric layer preserving the anisotropy produced by the flows which existed previously. The interaction of the stresses with cracks in the upper crust can be one of the causes of anisotropy in this layer. 相似文献
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Hideki Shimamura 《Geophysical Journal International》1984,76(1):253-260
Summary. A series of long-range explosion seismological experiments has been conducted by the use of specially designed ocean bottom seismographs (OBSs) in the Western Pacific. OBS studies of apparent velocity measurements by the use of natural earthquakes have also been made. The experiments have made clear that large-scale P -wave anisotropy exists in the entire thickness of the oceanic lithosphere. The existence of the large-scale anisotropy in the oceanic lithosphere has been demonstrated for the first time by seismic body-wave studies. Previously, anisotropy had been found only in the uppermost oceanic mantle in the Eastern Pacific.
The azimuth of the maximum velocity, 8.6 km s-1 , is about 155° clock-wise from north. The direction is perpendicular to the magnetic lineation of the region, however, the direction differs from the direction of the present plate motion by about 30°. So it appears that the anisotropy has been 'frozen' at least since the change of the plate motion that occurred 40 Myr ago. The frozen anisotropy should set important constraints on the mechanical properties of the lithosphere such as the viscosity and temperature of the lower lithosphere. 相似文献
The azimuth of the maximum velocity, 8.6 km s
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Thickness of the lithosphere east of the Dead Sea Transform 总被引：1，自引：0，他引：1
Ayman Mohsen Rainer Kind Stephan V. Sobolev Michael Weber the DESERT Group 《Geophysical Journal International》2006,167(2):845-852
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Observations of flexure and the rheology of oceanic lithosphere 总被引：2，自引：0，他引：2
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Rheology of the lithosphere in the East African Rift System 总被引：3，自引：0，他引：3
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A. L. Hales 《Geophysical Journal International》1991,105(2):355-363
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3-D structure of the lithosphere in the Aegean region 总被引：2，自引：0，他引：2
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