利用费希尔最优分割法划分临夏盆地早更新统地层孢粉带的初步研究

将费希尔（Fisher）最优分割法引入到临夏盆地早更新统东山组地层孢粉带的划分中，结合地层特征，共划分出了3个孢粉带。这3个孢粉带分别为：带Ⅰ（深度78．5～45．5m）柏科-禾本科组合带、带Ⅱ（深度45．5～12．5m）云杉属-榆属-禾本科组合带、带Ⅲ（深度12．5～0．5m）云杉属一禾本科组合带。孢粉带分带揭示，临夏盆地早更新世气候变化经历了干-湿-干3个阶段，这一结果同以往获得的粒度、碳酸钙和Cl-等无机指标高分辨率分析结果相一致。     

Postcumulus processes in oceanic-type olivine-rich cumulates: the role of trapped melt crystallization versus melt/rock interaction

Combined microstructural and geochemical investigations on MORB-type primitive olivine-rich cumulates intruded in the Erro–Tobbio (ET) mantle peridotites (Voltri Massif, Ligurian Alps, Italy) revealed that significant chemical changes in minerals were caused by postcumulus crystallization. This is indicated by the occurrence of accessory interstitial minerals (Ti-pargasite, orthopyroxene and Fe–Ti oxides) and by systematic chemical zoning in intercumulus clinopyroxene, resulting in marked trace element (e.g. REE, Ti and Zr) enrichment at constant high Mg-numbers (0.88–0.91) and LREE depletion. Geochemical modelling shows that low trapped melt amounts (<5%) are sufficient to produce the observed trace element enrichments. Chemical zoning in large (mm-size) clinopyroxenes was dominantly caused by in situ fractional crystallization of trapped interstitial liquid rather then porous flow migration of externally derived evolved melts. Zr enrichment relative to REEs in vermicular clinopyroxene and pargasitic amphibole point to small-scale migration and interaction between residual evolved low melt fractions and the olivine cumulus matrix at final stage of crystallization. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Earthquake fault rupture—shallow foundation interaction in undrained soils: a simplified analytical approach

The interaction between normal or reverse fault ruptures and shallow foundations resting on a homogeneous undrained soil layer is investigated. After performing a thorough set of non‐linear finite element simulations, three simple kinematic mechanisms are proposed to predict the conditions for the fault rupture to be diverted by the foundation. The results obtained by both numerical and analytical approaches are in good agreement, and support the adequacy of the proposed mechanisms. A relationship is established for assessing the minimum foundation bearing load needed for diversion of the fault rupture trace, either normal or reverse. This relationship is proved to be independent of the fault type and dip angle, so that it can be applied easily for engineering applications, even in the absence of specific tectonic information. Copyright © 2006 John Wiley & Sons, Ltd.     

Mitigation of the seismic motion near the edge of cliff-type topographies using anchors and piles

Concentration of damage of buildings near the edge of cliff-type topographies has been observed during a number of recent earthquakes and interpreted by numerical dynamic analyses that illustrate the amplification of the horizontal acceleration and the generation of parasitic vertical acceleration near the tip of slopes. The paper performs a detailed parametric numerical analysis to investigate the ability of mitigating this topographic effect using anchors and piles. A typical field case, the Aegion slope of Greece, is considered. Different input motions are applied. The results illustrated that anchors and piles can be effective in mitigating the topographic effect. The main issue is that if the part of the slope in which topographic amplification occurs is connected to that at larger depths, in which the acceleration is smaller, then the accelerations at the top of the slope have to become more uniform and smaller. For typical diameter and material properties of anchors/piles the effectiveness of the mitigation depends on the length, inclination, location and number of anchors/piles. An optimum configuration of anchors/piles mitigating the topographic effect is proposed.     

1987-2006年北方13省土地利用/覆盖变化驱动力分析

以北方13省为研究区,利用主成分分析与逐步多元回归分析方法,分析了研究区土地利用/覆盖变化的驱动机制.结果表明:(1)由于地域差异的原因,各个子区域中土地利用/覆盖类型变化的驱动因子有所不同;(2)社会经济要素是研究区土地利用/覆盖变化的主导驱动因子,尤其是人口因素发挥着重要作用;(3)气温、降水等自然因子对区域土地利用/覆盖变化也具有一定的制约作用,主要表现在东北和西北等受自然要素限制较为突出的地区.政策驱动因子在研究中没有得到反映,但不难判定国家生态环境政策无疑也对区域土地利用/覆盖的变化起到了非常重要的作用.     

Earthquake simulation test of circular reinforced concrete bridge column under multidirectional seismic excitation

1 Introduction Since the 1971 San Fernando earthquake, a signi?cant amount of research has been conducted on the ductility capacity of reinforced concrete bridge columns, resulting in signi?cant advances in the seismic design of bridges. Since most tests have been done in static or quasistatic conditions and unidirectional loading conditions, however, no method that properly evaluates the effect of multidirectional dynamic loading has been developed, and design recommendations on this effect a…     

地震资料非高斯信息分析提取方法及油气预测

从讨论实际地震记录高阶累积量分析入手,研究利用高阶累积量计算高阶谱的方法.在分析高阶累积量及高阶谱提取分离具有非高斯分布信号时,详细讨论了产生非高斯分布的地震记录的特征规律.阐明了用地震资料的低频高阶谱预测砂体含油气性的机理.从理论模型和实际资料论证了研究方法的正确性.最后利用该方法计算的高阶谱结果和实际产油气井资料进行符合率验证分析.在此基础上,利用该方法进行有利含油气层预测.     

赤道太平洋-印度洋海温异常综合模与次表层海温异常

通过对1958-2001年的SODA海温资料进行经验正交函数分解,得到了太平洋-印度洋海温异常综合模态,该模态在海表及次表层的时空演变特征的分析表明,在赤道西印度洋、中东太平洋的海温偏高(低)时,赤道西太平洋、东印度洋的海温偏低(高)。该综合模态既有年际变化特征,还有年代际变化特征,在20世纪70年代中后期由以负指数为主转变为以正指数为主。对1958-2001年强正、负指数事件合成分析结果得知,综合模也存在着显著的年变化特征,在2-4月份偏弱,最强出现在10月份。西太平洋暖池次表层与赤道东太平洋次表层、赤道东印度洋次表层与西印度洋次表层有一种反位相的变化。次表层海温异常在东太平洋、西印度洋分别沿着南北纬10°左右向西太平洋、东印度洋传播并向赤道扩展,西太平洋、东印度洋的次表层海温异常则分别沿赤道向东太平洋、西印度洋传播汇聚。     

孟加拉湾中部表层沉积物常微量元素地球化学:物源指示意义

通过对取自孟加拉湾中部的110个表层沉积物样品进行了常微量元素测试分析,探讨了其物质来源。在所有测试元素中,Si含量最高,其次为Al,且这两种元素的分布特征基本一致。化学蚀变指数（CIA^*）平均值为72.07,指示研究区沉积物风化程度位于喜马拉雅源区和印度源区沉积物之间。因子分析和判别函数计算分析表明研究区沉积物主要来自喜马拉雅源区和印度源区。使用Ti标准化后的元素比值反演模型估算的喜马拉雅源区和印度源区对研究区沉积物的相对贡献比例分别为83.5%和16.5%。其中,喜马拉雅源区对研究区东部沉积物贡献相对较大,而在研究区西部印度源区贡献比例相对东部为高。喜马拉雅源区物质向研究区输运的主要动力机制包括浊流及其溢流、表层季风环流携带的河流冲淡水,而印度源区物质主要通过表层季风环流特别是东印度沿岸流向研究区输运     

中国近海异常海温数值预报模式研究Ⅱ.因子分析和试预报

首先对近海异常海温模式的主要影响因子作了概量估计.在此基础上对形成异常高温和异常低温的有利天气系统、主要影响因子和形成时间尺度进行了比较,进而对试预报(后报)个例的选取、初值的形成、试预报结果及其检验进行了说明.最后对这一研究进行了总结和讨论.