GSFC（9/80）地磁模型的评价和中国地磁台站异常值的确定

本文利用1960-1980年中国地磁台站资料检验了GSFC（9/80）地磁模型,结果表明该模型是成功的。据此通过地磁台站1960-1980年的观测值与GSFC（9/80）模型计算值的比较,确定了中国地磁台站的异常值。本文还建议在基本磁场的研究中从台站观测年均值中减去较精确测定的台站磁异常值,以提高资料的精确度。     

基于新疆分量式钻孔应变异常类型的地震强度预测研究

研究了钻孔应变年变畸变型异常及指数型异常对地震震级的估计问题,认为年变畸变型异常对大震有较高的映震性能.研究了异常幅度和震中距、时间分布和震级关联问题,结果表明,在时间小于45天时,震级和发震时间呈反比,在时间大于45天时,震级和发震时间呈正比.     

Exceptional preservation of Upper Carboniferous (lower Westphalian) fossils from Edlington,Doncaster, South Yorkshire,UK

A new fossil‐bearing, Upper Carboniferous (lower Westphalian) locality in Doncaster, South Yorkshire, UK, is reported and an account of the fossils is presented. The diverse flora and fauna consists of plants, bivalves, arthropods (primarily xiphosurans), tentaculitids (microconchids), fish scales, shark egg capsules and coprolites. Fossils are preserved in siderite nodules and shales, and display excellent preservation and detail. Previous collecting of Carboniferous fossils in the Doncaster area has been minimal. The discovery of this locality addresses this deficit and is of further importance as such localities in the UK are diminishing in number with the cessation of coal‐mining and the reclamation of mine dumps, further demonstrating the importance and recognition of the Edlington site. Copyright © 2014 John Wiley & Sons, Ltd.     

Influence of shear heating on microstructurally defined plate boundary shear zones

In plate-boundary scale ductile shear zones defined by microstructural weakening, shear heating may lead to a temperature increase over 5 m.y. of up to 80 °C just below the brittle ductile transition, up to 120 °C just below the Moho, and to thermal boundary zones tens of km wide on either side of the shear zone. Where rock strength is highest, shear zones are narrow (∼1 km), and thermal gradients within the shear zone itself are low, so there is no tendency for increased localization. Heating results in thermal weakening, but this is partly offset by grain growth related to the decrease in stress. In shear zones of the order of 10 km width, shear stress, strain rate, and hence heat generation are lower, and thermal gradients are insufficient to cause additional strain localization. Temperature increases in the mid-crust are of the order of 10 °C, insufficient to cause partial melting or an increase in metamorphic grade. In the upper mantle, shear zones may be 50 km or more wide, and the temperature increase is less than 20 °C in 5 m.y., but temperature differences between center and margin may enhance the strain rate at the center by up to 18%.     

漳州台深井应变不变量同震响应分析

在解决钻孔应变观测加衬模型的待定常数的基础上,巧妙地利用不变量与坐标系选择无关的性质,推导出了5组观测组合计算不变量的简洁表达式,并以玉树地震为例,选取漳州台深井观测系统的探头上、下端面8分量应变观测单元的观测资料,采用加衬模型分别根据探头上下端面的5组观测组合公式计算了地震当天的最大主应变、最小主应变、最大主应变相应...     

Modeling shear behavior and strain localization in cemented sands by two-dimensional distinct element method analyses

This paper presents a numerical investigation of shear behavior and strain localization in cemented sands using the distinct element method (DEM), employing two different failure criteria for grain bonding. The first criterion is characterized by a Mohr–Coulomb failure line with two distinctive contributions, cohesive and frictional, which sum to give the total bond resistance; the second features a constant, pressure-independent strength at low compressive forces and purely frictional resistance at high forces, which is the standard bond model implemented in the Particle Flow Code (PFC2D). Dilatancy, material friction angle and cohesion, strain and stress fields, the distribution of bond breakages, the void ratio and the averaged pure rotation rate (APR) were examined to elucidate the relations between micromechanical variables and macromechanical responses in DEM specimens subjected to biaxial compression tests.     

On the efficiency and predictability of strain energy for the evaluation of liquefaction potential: A numerical study

Strain energy concept has been employed by the researchers for the assessment of liquefaction phenomenon which is a disastrous type of earthquake-induced failure in saturated soils. The efficiency and predictability conditions of strain energy concept for liquefaction potential assessment are investigated herein using effective stress numerical analyses. Several earthquake ground motions were introduced to the base of a calibrated numerical model using an advanced fully coupled constitutive model. Results of the numerical analyses indicate that earthquake-induced excess pore pressure is more rigorously proportional to strain energy compared with the other examined intensity measures. Subsequently, a simple relationship was derived using the results of dynamic analyses to predict cumulative strain energy density in terms of magnitude, source to site distance, and effective overburden pressure. This relationship, which tries to guarantee the predictability condition of strain energy demand, has demonstrated a successful capability in discrimination between the liquefied and non-liquefied case histories recorded after several well-known earthquakes. This study has provided a practical linkage between numerical analysis and field observations. Finally, it is concluded that although strain energy approach possesses a great conceptual efficiency in liquefaction potential assessment, its precise prediction in actual field conditions involves some difficulties.     

Numerical analysis of a cylinder moving through rate-dependent undrained soil

Geo-hazard assessment of the potential damage to a pipeline caused by a submarine landslide requires a quantitative model to evaluate the impact forces on the pipeline. In contrast with typical geotechnical problems, the strain rate within the fast moving, flow-like submarine landslide is typically far higher, which will lead to enhancement of the soil strength and therefore result in larger impact forces. Generally, there are two possible predictive frameworks for strain-rate dependence: a fluid dynamics framework and a geotechnical framework. By comparison of common rheological models adopted in these two different approaches, a unified additive power-law model, a normalised form of the Herschel-Bulkley model from fluid mechanics, is explored in this paper. This model has been used in conjunction with a large deformation finite element approach to investigate the undrained limiting loads on a cylinder moving steadily through inertia-less soft rate-dependent material, in order to quantify the strain-rate effects.The flow mechanism and the effects of the shear-thinning index and Oldroyd number on the shear zones are explored. The calculated resistance factors are compared with the drag coefficients obtained from computational fluid dynamics analysis. The average rate of strain experienced by the soil flowing past the cylinder is estimated for a given flow velocity and an expression in the form of a conventional bearing capacity equation, but with shear strength linked directly to the normalised flow velocity, is proposed to predict the magnitude of the viscous force exerted by the debris flow.     

主汛期(6～8月)副高各指数与中国160站降雨的关系

利用1951～2001年共51年6～8月副高5个指数与同期中国160站降雨建立标准化的多元回归方程,通过分析副高5个指数的偏回归系数及各方程复相关系数在时间和地域上的分布和变化,研究了副高各指数所反映的位置、形状、面积、强度等特征对我国主汛期降雨的综合影响以及这种影响在季节和地域上的差异,结果表明副高北界位置指数和脊线位置指数主要影响雨带位置的变化,西伸脊点指数与我国大部地区雨量的丰欠有关,面积和强度指数则由于采用的方法而表现出对降雨的影响呈相反的特性.从副高对我国主汛期降雨的拟合能力上看,7月拟合能力比6月和8月好,对东部地区和华南地区的拟合能力分别比西部地区和华北地区好.     

利用一维资料重现n维系统吸引子结构的试验

以Ｒｏｓｓｌｅｒ系统和Ｌｏｒｅｎｚ系统为例，研究了利用单变量时间序列来重现ｎ维动力吸引子的枯朴结构，研究结果表明，在一维时间序列重建的相空间里，存在着若干个主矢量，这些主矢量可以从某一侧面揭示出系统吸收子的枯扑系统。