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151.
安维光  郭宝娥 《山西地震》1994,(2):17-20,26
对阳原台1979年4月至1992年6月的ρ_s月均值,用差值法消除年变以后,突出了正常背景和异常特征。得出消除年变后的ρ_s月差值,反映台站220km内5级以上地震的效果是好的结论。  相似文献   
152.
粤西玻璃陨石的发现及其断代意义   总被引:5,自引:1,他引:5  
对粤西电白、茂名、吴川一带发现的玻璃陨石(雷公墨),进行了年代和化学成分测定,证明它们和邻近的雷琼地区以至澳亚散布区内其它地区的玻璃陨石一样,是同一地质事件的产物。本文根据雷公墨所在层位,大体确定了若干第四系剖面的时代,为判断吴川-四会断裂带的近期活动提供了依据。  相似文献   
153.
基于弹性理论的顺层边坡失稳破坏力学模型分析   总被引:4,自引:1,他引:3  
在分析顺层边坡受力状况的基础上,当边坡的坡脚未被破坏时,将顺层边坡视为弹性地基上的悬臂梁,由此提出其失稳破坏的力学模型。应用弹性理论求出在力作用下悬臂梁的应力状态,并根据摩尔-库伦准则,导出可判定其稳定性的安全系数计算公式,得出了顺层边坡处于极限平衡状态极限长度。同时通过实例计算,将文中方法与应用突变理论所得结果对比,验证了本文方法的可行性。  相似文献   
154.
Wang  Yanjun  Zhu  Weiguang  Zhong  Hong  Bai  Zhongjie  Yao  Junhua  Xu  Chong 《中国地球化学学报》2019,38(3):376-390

The Pingchuan iron deposit, located in the Yanyuan region of Sichuan Province, SW China, has an ore reserve of 40 Mt with ~ 60 wt% Fe. Its genesis is still poorly understood. The Pingchuan iron deposit has a paragenetic sequence of an early Fe-oxide–Pyrite stage (I) and a late Fe-oxide–pyrrhotite stage (II). Stage I magnetite grains are generally fragmented, euhedral–subhedral, large-sized crystals accompanying with slightly postdated pyrite. Stage II magnetite grains are mostly unfragmented, anhedral, relatively small-sized grains that co-exist with pyrrhotite. Combined with micro-textural features and previously-obtained geochronological data, we consider that these two stages of iron mineralization in the Pingchuan deposit correspond to the Permian ELIP magmatism and Cenozoic fault activity event. Both the Stage I and II magnetites are characterized with overall lower contents of trace elements (including Cr, Ti, V, and Ni) than the ELIP magmatic magnetite, which suggests a hydrothermal origin for them. “Skarn-like” enrichment in Sn, Mn, and Zn in the Stage I magnetite grains indicate significant material contributions from carbonate wall-rocks due to water–rock interaction in ore-forming processes. Stage II magnetite grains contain higher Mn concentrations than Stage I magnetite grains, which possibly implies more contribution from carbonate rocks. In multiple-element diagrams, the Stage I magnetite shows systematic similarities to Kiruna-type magnetite rather than those from other types of deposits. Combined with geological features and previous studies on oxygen isotopes, we conclude that hydrothermal fluids have played a key role in the generation of the Pingchuan low-Ti iron deposit.

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155.
基于引力模型的海洋锋信息提取   总被引:2,自引:0,他引:2  
海洋锋面是海洋水团特性明显不同的两种或几种水体之间的狭窄过渡带。本文旨在对遥感反演海洋温度场数据(SST),引入引力模型进行海洋锋面的检测。鉴于海洋锋受噪声干扰大,锋面强度小的特点,本文提出了基于引力算法的引力模型。其中,引力算法是将温度数据中的每一个像元点都作为一个独立的天体,其质量对应该像元的温度值,根据引力定律计算3×3区域中,邻域像元对中心点像元的引力和。模型首先对原始数据进行去0处理,为消除对原始数据明暗程度的依赖,对3×3区域数据进行归一化,然后利用函数对归一化后的数据进行增强处理,最后,以引力算法进行锋面检测。验证表明,该模型能有效强化不同区域或水体差异性,并能够有效针对海洋锋信息进行提取,受噪声影响小。  相似文献   
156.
一种基于Bancroft算法的GPS动态抗差自适应滤波   总被引:3,自引:0,他引:3  
基于抗差自适应滤波的思想,结合非线性Bancroft算法的特点,提出了一种基于Bancroft算法的GPS动态抗差自适应滤波。计算表明,该算法不仅在一定程度上减弱了由于线性化忽略高次项对导航解的影响,而且再次证实抗差自适应滤波在控制扰动异常的有效性和合理性。  相似文献   
157.
一次华南暖区暴雨过程可预报性的初值影响研究   总被引:4,自引:0,他引:4  
华南暖区暴雨发生时,冷空气和锋面离广东较远,往往事前不易被发现,漏报或迟报较多。基于覆盖华南区域的3 km GRAPES_Meso模式和ADAS(ARPS Data Analysis System)系统的复杂云分析方案,选取2015年5月16日发生在粤西沿海地区的一次暖区暴雨个例进行数值试验,研究模式初始湿度条件的差异对暖区对流系统的触发、发展和维持的可预报性的影响。试验结果表明,增加模式的初始云信息可以增大初始场中低层的大气湿度,使空气接近或达到饱和,从而使数值模式有能力模拟出与实况接近的降水。分析模拟结果的对流触发和维持过程,可以发现,(1)初始水汽和云水物质的增多,增大了大气的不稳定性:对流有效位能(CAPE)增大、K指数增大,对流抑制能量(CIN)减小、抬升指数(LI)减小,而且大气可降水量(PW)增多,从而使对流能够被快速激发;(2)暖区暴雨对流触发和对流维持的机制有所不同:模式对初始时刻湿度条件高度敏感,模式开始积分后饱和大气释放凝结潜热加热大气,所导致的浮力增强使对流更容易被触发;对流维持发展阶段,降水引发地面弱冷池形成,冷池向外流出气流与粤西沿海暖湿气流的汇合维持了低层水平风场辐合,从而维持了对流和降水的发展。进一步的敏感性试验表明,减少初始水汽增量,则辐合上升运动减弱,激发的对流强度减弱,且对流发生、发展、消散的速度变慢、滞后于实况。   相似文献   
158.
Liu  Weiguang  Wang  Guiling  Yu  Miao  Chen  Haishan  Jiang  Yelin  Yang  Meijian  Shi  Ying 《Climate Dynamics》2020,55(9-10):2725-2742

The future vegetation–climate system over East Asia, as well as its dependence on Representative Concentration Pathways (RCPs), is investigated using a regional climate–vegetation model driven with boundary conditions from Flexible Global Ocean–Atmosphere–Land System Model: Grid-point Version 2. Over most of the region, due to the rising CO2 concentration and climate changes, the model projects greater vegetation density (leaf area index) and gradual shifts of vegetation type from bare ground to grass or from grass to trees; the projected spatial extent of the vegetation shift increases from RCP2.6 to RCP8.5. Abrupt shifts are projected under RCP8.5 over northeast China (with grass replacing boreal needleleaf evergreen trees due to heat stress) and India (with tropical deciduous trees replacing grass due to increased water availability). The impact of vegetation feedback on future precipitation is relatively weak, while its impact on temperature is more evident, especially during DJF over northeast China and India with differing mechanisms. In northeast China, the projected forest loss induces a cooling through increased albedo, and daytime high temperature (Tmax) is influenced more than nighttime low temperature (Tmin); in India, increased vegetation cover induces an evaporative cooling that outweighs the warming effect of an albedo decrease in DJF, leading to a weaker impact on Tmax than on Tmin. Based on a single model, the qualitative aspects of these results may hold while quantitative assessment will benefit from a follow-up regional model ensemble study driven by multiple general circulation models.

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159.
以储层敏感性流动实验为基础,结合X射线衍射、扫描电镜、铸体薄片等方法,对松辽盆地扶新隆起带北部扶余油层超低渗储层粘土矿物特征及其对储层敏感性的影响进行了研究,结果表明:扶余油层主要含有绿泥石、伊利石、高岭石和伊/蒙混层等4种矿物,其中伊利石含量最多,绿泥石和伊/蒙混层次之,高岭石最少。储层速敏性和碱敏性相对较弱,水敏性和盐敏性较强,对储层影响较大,勘探开发时应重点关注。粘土矿物对储层水敏性的影响主要有3个方面,其中粘土矿物绝对总量是扶余油层水敏性强弱的主控因素。  相似文献   
160.
Platinum-group elements (PGE) in PGE-rich porphyry copper (gold) deposits are mainly Pt and Pd, whereas the concentrations of other PGE (Ru, Rh, Os, Ir) are significantly low. Moreover, Pt and Pd mainly exist in sulfides in the forms of crystal lattice or tiny platinum-group mineral (PGM) inclusions. The present data show that there is a positive relationship between Pt and Pd concentrations and Cu (Au) in porphyry copper (gold) deposits. The comparison of chondrite-normalized PGE distribution patterns between the ore-bearing porphyry intrusions and ore-barren porphyry intrusions in arc setting, 187^Os/188^Os, 87^Sr/86^Sr and S isotopes for porphyry copper (gold) deposits shows that PGEs were mainly derived from the mantle, and fluids from subduction zones devoted trivial PGE to the magma. The porphyry copper (gold) deposits associated with subducted events are most probably enriched in PGE, whereas those related to crustal thickening, lithospheric delamination or underplating rarely concentrate PGE. The osmium isotopic compositions in porphyry copper (gold) deposits reveal that (187^Os/188^Os)i values are highly variable and not lower than those of primitive upper mantle (PUM) and mantle peridotite, however, osmium concentrations are commonly lower than mantle peridotite, suggesting that parental magmas of some porphyry intrusions had experienced crustal contamination during magma evolution. Experimental investigations have proved that PGE exist in the forms of Cl^- and HS^- complexes during transportation and migration of the oreforming fluids. This paper summarizes previous studies including crucial controlling factors and mechanisms for PGE enrichment, and points out that the mantle-derived magmas parental to porphyry intrusions are the prerequisite for PGE enrichment in porphyry copper (gold) deposits. Favorable physical and chemical conditions (including salinity, temperature, pressure, pH, and oxygen fugacity) in hydrothermal fluids crucially control the  相似文献   
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