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991.
To determine the locked and slip parts on a fault,we simulated the movement pattern of the fault with a combined model consisting of a negative dislocation in the locked area superimposed on a relative movement between two sides of the fault.In this way,we determined the locked parts of faults by inversion with multiple epochs of geodetic data.In this paper,we have determined the movement patterns of four main faults in western Yunnan by inversion with two epochs of geodetic surveys and some crossing-fault observations.From the inversion result,we have identified the areas around Dali and Xiangyun to be the locked area,which is regarded as a sign of potential earthquake sources. 相似文献
992.
993.
混合层厚度,风速和稳定度对地面SO2浓度分布影响的数值试验 总被引:1,自引:5,他引:1
利用Euler平流扩散方程和K模式闭合方案的数值解,讨论了混合层厚度、风速和稳定度3因子对银川市冬季地面SO_2浓度分布的影响。结果表明,在极不稳定层结(A级)下混合层厚度增加250m时能使地面SO_2浓度减少40%~75%,而在稳定层结下混合层厚度增加200m时仅减少20%的浓度;而当混合层厚度和风速分别增加250m和3.8m·s ̄(-1)、层结由稳定(F)变为极端不稳定(A),并且当混合层最大厚度和最大风速分别限制在650m和4m·s ̄(-1)时,老城西部地面浓度减少了90%,稀释效应最显著。 相似文献
994.
995.
996.
REE Biological Metallogeny —A Preliminary Study 总被引:3,自引:2,他引:3
Five species of bacteria have been found in granite-weathering profiles of Ore District 701.They tend to decrease in varieties and quantities from the upper part down-ward, and no bacterium has been brought up below the depth of 10 m.The simulating experiments done by using humic acid of small molecular weight ,and decanedioic acid extracted from the samples and the bacteria mentioned above have shown that:(1)The dissolving rates of REEs from humic acid original rock or decanedioic acid original rock are lower than those from humic acid bacteria original rock or decanedioic acid bacteria original rock.The presence of bacteria may accelerate the formation of REE-organic complexes and make the complexes increase in quantity.Aminoacids in the bacteria are involved in coordination balance.The concentrations of the complexes tend to increase as a result of the formation of the complexes,i.e., the dissolution, complexation, migration and accumulation of REEs from the original rocks will be accelerated.(2)The metabolism of microorganisms has contributed a lot to keeping a pH environment in the weathering crust. 相似文献
997.
A NUMERICAL EXPERIMENT STUDY ON THE FORMING MECHANISMS OF LOW-LATITUDE CIRCULATION CELLS AND PRECIPITATION DURING AN EAST ASIAN COLD SURGE 下载免费PDF全文
The forming mechanisms of low-latitude circulation cells and precipitation during an East Asian cold surge have been studied by using a five-layer primitive equation model.Numerical experiments show that in mid-high latitudes,the propagation of the East Asian winter monsoon is nearly a dry process;in low-latitudes,the effects of cumulus convection intensify the northeast monsoon and northeast trade wind;however,they also prevent the intertropical convergence zone(ITCZ) from further southward invasion,and strengthen the meridional and zonal cells over East Asia. Numerical results also indicate that the winter monsoon precipitation in Indonesia and Northern Australia can exist independently.Both the South China Sea(SCS) cold surge and the West Pacific northeast cross-equatorial trade wind are of importance for the formation of the Northern Australia summer monsoon and its precipitation.Numerical results show that the development of cumulus convection,triggered by the SCS cold surge,is a crucial factor in forming the heavy monsoon precipitation and low-level stationary disturbances in Indonesia and Borneo.The tropical topography and northeast trade wind disturbances only affect the intensity of precipitation there. 相似文献
998.
工程地质测试技术与方法 总被引:2,自引:0,他引:2
张苏民 《水文地质工程地质》1993,20(1):38-41
本文分别论述了室内试验,原位测试,资料整理及数值分析方法、地基加固4个方面所取得的进展,并指出存在问题及努力的方向 相似文献
999.
Abstract Phase transformations in model mantle compositions and those in subducting slabs have been reviewed to a depth of 800 km on the basis of recent high-pressure experimental data. Seismic velocity and density profiles in these compositions have also been calculated using these and other mineral physics data. The nature of the seismic velocity and density profiles calculated for a pyrolite composition was found to generally agree with those determined by seismic observations (e.g. PREM). The locations of the seismic discontinuities at 400 and 670 km correspond almost exactly to the depths where the transformations of the olivine component to denser phases take place. Moreover, the steep gradients in the seismic velocity/density profiles observed between these depths are qualitatively consistent with those expected from the successive transformations in the complementary pyroxene-garnet component in the pyrolite composition. Further, the calculated seismic velocity and density values agree well with those observed in the upper mantle and mantle transition region within the uncertainties attached to these calculations and observations. Pyrolite or peridotite compositions are thus most likely to represent the composition of the mantle above 670 km depth, although some degrees of chemical heterogeneity may exist in the transition region. The observed sharp discontinuous increases of seismic velocities and density at this depth may be attributed either to the phase transformation to a perovskite-bearing assemblage in pyrolite or to chemical composition changes. Density profiles in subducted slabs have been calculated along adequate geotherms assuming that the slabs are composed of the former oceanic crust underlain by a thicker harzburgitic layer. It is shown that the former oceanic crust is substantially less dense than the surrounding pyrolite mantle at depths below 670 km, while it is denser than pyrolite in the upper mantle and the transition region. The subducted former oceanic crust may be trapped in this region, forming a geochemically enriched layer at the upper mantle-lower mantle boundary. Thick and cool slabs may penetrate into the lower mantle, but the chemically derived buoyancy may result in strong deformation and formation of megalith structures around the 670 km seismic discontinuity. These structures are consistent with those detected by recent seismic tomography studies for subduction zones. 相似文献
1000.
鉴于方解石是研究低温碳酸盐型汞矿床构造应力作用的良好对象,作者对贵州丹寨汞矿床中24件方解石样品进行构造形变及构造成矿模拟试验,经光学显微镜及透射电子显微镜对比观察指出:多种应力作用叠加及微观构造形变的先后生成关系,可视为多期次构造动力作用的结果;汞矿的成矿作用和构造作用的相关和同步性,说明构造作用既可提供成矿的空间,又是促进成矿的动力。 相似文献