地球主磁场的能量密度谱及其长期变化

根据BJ地磁场模型和第8代国际地磁参考场(IGRF)模型，计算并分折了1690～2000年期间地球表面主磁场和分量的能量密度谱及其长期变化。结果表明1690～2000年期间主磁场的能量密度谱一直在减小，其主要原因是由于偶板子磁场的衰减产生的，而非偶板子磁场的能量密度谱在1690～1780年期间减小，1780～1890年增大，1890年以后快速增大。在地磁场总能谱的变化中，Z分量的贡献起主要作用。能量密度随谐波阶数的变化在半对数坐标中近似线性，非偶板子场的等效磁源深度位于核幔边界附近，n＝1，2谐波项的等效磁源位于地球内核边缘，其位置随时间变化。1780和1890年前后是地磁场变化的转折时期。能量密度谱的长期变化存在大约60a的周期规律。     

洱海地区一万多年以来气候环境演化的湖泊沉积记录

根据对洱海北部10．8m深水区ES孔沉积物高分辨率的孢粉、粒度、碳屑、藻类分析,结合AMS^14C测年数据,划分了11个阶段,恢复了一万多年以来云南洱海地区气候环境演化序列．全球性的降温事件在该地区都有明显的反映,包括9900aBP(Younger Dryas)、8500aBP、7100aBP、5100aBP左右的四次冷事件,6800—5500aBP为全新世水热配置最佳期,距今2400年开始该地区出现较为明显的人类活动．     

突出小地震活动事件作为中强震短临预报判据的研究

对新疆1970年以来突出小震活动事件进行了统计分析,给出突出小地震活动事件与5级以上中强震的对应关系,提出以突出小地震活动事件中小地震发生的时间间隔和频度预报中强震的短期判据。     

Development of U–Pb dating of uraninite using a secondary ion mass spectrometer: Selection of reference material and establishment of calibration method

A method for U–Pb isotopic dating using secondary ion mass spectrometer (SIMS) was developed for uraninite. Correlation between ²⁵¹(UO)⁺/²³⁵U⁺ and ²⁰⁶Pb⁺/²³⁵U⁺ obtained by a sensitive high‐resolution ion microprobe (SHRIMP) was adopted for a calibration from secondary ion ratios (Pb⁺/U⁺) to the atomic abundance ratios (Pb/U). In this study, a uraninite sample (²⁰⁶Pb/²³⁸U = 0.1647) collected from Faraday mine, Bancroft, Canada, is used as a reference material for the U–Pb calibration. The established method was applied to three uraninite samples collected from the Chardon, Ecarpière, and Mistamisk mines. The calibrated ²⁰⁶Pb^*/²³⁸U ratios of the three uraninites show correlation with Pb/U elemental ratios obtained using an electron probe microanalyzer (EPMA) (correlation coefficients: 0.98, 0.99, and 0.97, respectively), which indicates the reliability of the SHRIMP calibration method used in this study. The analysis of Ecarpière uraninite provides concordant U–Pb data, and a weighted average of the ²⁰⁶Pb^*/²³⁸U age is 287 Ma ±8 Ma (95 % conf.) which is consistent with the previous chronological results by SIMS. Mistamisk uraninite provides discordant U–Pb data with the upper and lower intercept ages of 1 729 and 421 Ma, which correspond to uraninite formation in association with the Hudsonian orogeny and the remobilization of uranium as pitchblende, respectively. The U–Pb age of Chardon uraninite (315 Ma) is consistent with the igneous activity of Mortagne granite, but is older than the previously reported age (264 Ma). Marcasite in the Chardon uraninite altered to goethite under the oxidizing condition, which indicates that U–Pb system in the uraninite crystallized at 315 Ma was disturbed under the oxidizing condition. The established calibration method using Faraday uraninite is useful for U–Pb isotopic dating on the scale of a few micrometers to tens of micrometers, which make it possible to obtain the accurate age of uraninite.     

1690年以来全球非偶极子磁场的变化特征

根据J Bloxham和A Jackson地磁场模型，计算和分析了1690-1990年期间非偶极子磁异常的变化特片。结构表明，1690年以来一直存在的变化磁异常有7个，在一定时期内出现的磁异常有3个，它们是1830年以后出现的北太平洋负磁异常、1850年以后出现的东南太平洋负磁异常和1690-1900年期间在南太平洋地区出现的负磁异常。各个磁异常的强度和中心位置随时间变化，变化趋势各不相同。与根据IGRF模型计算的20世纪的磁异常变化比较，除非洲负磁异常外，两种模型得出的其它磁异常在同一时段内的变化趋势基本一致。     

Stochastic nature of three dimensional bursting events and sediment entrainment in vortex chamber

In this study, three dimensional quadrant analysis of bursting process was used to recognize the susceptible regions for sediment entrainment and deposition at the bed of a vortex chamber. From the analysis, it was found that two dimensional quadrant analysis in unable to find the turbulent coherent structure of flow near the bed of the vortex chamber. Therefore, a new method based on three dimensional bursting process is introduced in this study to define the turbulent flow structure. Based on the new methodology in this study, the bursting event is divided into eight different cube zones according to three dimensional velocity fluctuations. It was realized that, four cube zones interactions are toward the central orifice of the vortex chamber and four cube zones interactions are toward the wall of the chamber and they are categorized as classes A and B, respectively. The results from the experiments showed that in class A, the internal sweep events (class IV-A) moves the settled sediment particles toward the central orifice of the chamber, whereas in class B the external sweep events (class IV-B) moves the settled sediment particles toward the external region of the chamber. Also the transition probabilities of the bursting events in 64 particular movements were determined. The result showed that stable organizations of each class of the events had highest transition probabilities whereas cross organizations had lowest transition probabilities. Additionally, an effort was made to find the average inclination angle of the three dimensional bursting events in each cube zone. The results showed that near the bed of the vortex chamber by increasing the tangential velocity toward the center of the chamber, the average inclination angle of the events in the cube zones decreased. Also, at the region where the sediment particles were deposited, the inclination angles had higher values.     

地震预警技术研究中的参考文献

针对潜在破坏性大地震的早期预警系统已在几个发达国家或地区运行多年,并已积累了很多成功的经验。本文收集整理了国内外有关地震预警系统研究的参考文献,以供相关领域研究者参考之用。     

Determination of Reference Values for NIST SRM 610–617 Glasses Following ISO Guidelines

We present new reference values for the NIST SRM 610–617 glasses following ISO guidelines and the International Association of Geoanalysts’ protocol. Uncertainties at the 95% confidence level (CL) have been determined for bulk‐ and micro‐analytical purposes. In contrast to former compilation procedures, this approach delivers data that consider present‐day requirements of data quality. New analytical data and the nearly complete data set of the GeoReM database were used for this study. Data quality was checked by the application of the Horwitz function and by a careful investigation of analytical procedures. We have determined quantitatively possible element inhomogeneities using different test portion masses of 1, 0.1 and 0.02 μg. Although avoiding the rim region of the glass wafers, we found moderate inhomogeneities of several chalcophile/siderophile elements and gross inhomogeneities of Ni, Se, Pd and Pt at small test portion masses. The extent of inhomogeneity was included in the determination of uncertainties. While the new reference values agree with the NIST certified values with the one exception of Mn in SRM 610, they typically differ by as much as 10% from the Pearce et al. (1997) values in current use. In a few cases (P, S, Cl, Ta, Re) the discrepancies are even higher.     

Speciation of Chromium in Artificially Contaminated Soil Reference Material GSJ JSO-2 Using XANES and Chemical Extraction Methods

The oxidation states of chromium in GSJ JSO-2 (artificially contaminated soil) and three other geochemical reference materials (GSJ JSO-1, JLS-1 and JMS-1) were observed using X-ray near edge structure (XANES). For comparison, other artificially contaminated soil materials (mimic-JSO-2) were prepared by adding Cr(VI) into JSO-1. Their oxidation states of chromium were determined using XANES. The chromium contents were 1118 μg g^-1 for JSO-2, 1352 μg g^-1 for mimic-JSO-2 and 69-113 μg g^-1 for the other reference materials. Most chromium was present as hexavalent in mimic-JSO-2. No hexavalent species were detected in other samples. These results for chromium oxidation state in JSO-2 and mimic-JSO-2 obtained with XANES resembled those obtained from a chemical extraction method. The present JSO-2 has no trace of Cr(VI), although Cr(VI) was added as a major species during preparation. On the other hand, the content of Cr(VI) obtained in mimic-JSO-2 agreed with the original Cr(VI) content. A time-elapse study showed that Cr(VI) contents in mimic-JSO-2 decreased gradually to 70% of the original abundance during 240-day preservation in dry conditions. Moreover, the abundance of Cr(VI) decreased markedly to 15% after 240 days in the wet mimic-JSO-2 containing 20% m/m of water. These experiments suggested that soil humidity enhanced the reduction of Cr(VI) and that Cr(VI) was reduced even in dry conditions. Consequently, it is reasonable to infer that Cr(VI) doped into JSO-2 was completely reduced to Cr(III) during the preservation period of 5 years. The certification of the long-term stability of the chemical form in reference materials will be much more important in future.