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首页> 外文期刊>Geochemistry, geophysics, geosystems >The Cathles Parameter (Ct): A Geodynamic Definition of the Asthenosphere and Implications for the Nature of Plate Tectonics
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The Cathles Parameter (Ct): A Geodynamic Definition of the Asthenosphere and Implications for the Nature of Plate Tectonics

机译：锯切参数（CT）：近距离的地球动力学定义和板块构造性质的影响

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A weak asthenosphere, or low-viscosity zone (LVZ), underlying Earth's lithosphere has played an important role in interpreting isostasy, postglacial rebound (PGR), and the seismic LVZ, as well as proposed mechanisms for continental drift, plate tectonics, and postseismic relaxation. Consideration of the resolving power of PGR, postseismic relaxation, and geoid modeling studies suggests a sublithospheric LVZ perhaps ~100-200 km thick with a viscosity contrast of ~100-1,000. Ab initio numerical models of plate-like boundary layer motions in mantle convection also suggest a key role for the LVZ. Paradoxically, a thinner LVZ with a strong viscosity contrast is most effective in promoting plate-like surface motions. These numerical results are explained in terms of the reduction in horizontal shear dissipation due to an LVZ, and a simple scaling theory leads to somewhat nonintuitive model predictions. For example, an LVZ causes stress magnification at the base of the lithosphere, enhancing plate boundary formation. Also, flow within the LVZ may be driven by the plates (Couette flow), or pressure-driven from within the mantle (Poiseuille flow), depending upon the degree to which plates locally inhibit or drive underlying mantle convection. For studies of the long-wavelength geoid, PGR, and mantle convection, a simple dimensionless parameter controls the effect of the LVZ. This "Cathles parameter" is given by Ct = η*(D/λ)~3, where η* is the viscosity contrast, D is the thickness of the LVZ, and λ is the flow wavelength, emphasizing the tightly coupled trade-off between LVZ thickness and viscosity contrast. Summary The Earth's global system of tectonic plates move over a thin, weak channel ("low-viscosity zone") in the mantle immediately underlying the plates. This weak channel is commonly referred to as the asthenosphere, and its presence accounts for a number of important Earth observations, including isostasy (e.g., support for the uplift of large mountain ranges), t
机译：地球岩石圈的弱嗜患者或低粘度区（LVZ）在解释奥斯塔斯塔斯，后螺旋形反弹（PGR）和地震LVZ中发挥了重要作用，以及欧洲漂移，板块构造和后近的提出机制松弛。考虑到PGR，后发后弛豫和大溪地建模研究的解决力，表明副间位型LVZ可能〜100-200公里，粘度对比度为〜100-1,000。 AB Initio Mantle对流中的板状边界​​层运动的数值模型也表明LVZ的关键作用。矛盾的是，具有强粘度对比度的更薄的LVZ在促进板状表面运动方面最有效。这些数值结果是根据LVZ由于LVZ的水平剪切耗散的降低来解释的，并且简单的缩放理论导致稍微非直接模型预测。例如，LVZ导致岩石圈底部的应力放大，增强板边界形成。而且，LVZ内的流动可以由板（沟槽流动）驱动，或者从地幔（Poiseuille流量）内的压力驱动，这取决于板局部抑制或驱动下面的地幔对流的程度。用于研究长波长大型木偶，PGR和地幔对流，简单的无量纲参数控制LVZ的效果。该“锯切参数”由Ct =η*（d /λ）〜3给出，其中η*是粘度对比度，d是LVZ的厚度，λ是流量波长，强调紧密耦合的折射率在LVZ厚度和粘度对比之间。发明内容地球的全球构造板系统在立即底板上的地幔中移动薄，弱通道（“低粘度区”）。这种弱渠道通常被称为近际圈，其存在占多种重要地球观测，包括患者（例如，支持大型山区范围的隆起），T

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