近地表速度结构的地脉动探测方法国际盲比检验

本文通过参加ESG2006组织的国际地脉动盲比测验,检验了利用地脉动方法探测近地表速度结构的精度和可信度.在对多个不同测试模型频散曲线的提取精度、速度结构平均速度相对偏差和场地放大效应估计等方面的比较中,本文方法在参加盲比测验的19个国际研究组中均处于前列.同时盲比测验结果表明,不论人工合成记录还是实际观测记录、速度还是加速度记录,地脉动空间自相关方法得到的场地瑞利波频散曲线,均能够为后续反演研究提供可靠的目标曲线;可以根据仪器实际情况自由选择观测加速度或速度.人工合成数据分析中,有两例频散曲线受到了高阶振型影响,在实际观测数据中影响不明显.结合盲比测验结果指出,空间自相关方法的最大可探测波长一般达不到通常认为的15.7倍的最大半径,大多情况小于10倍;而最小波长要小于2倍的最小半径,可以到1倍的最小半径.     

VSOP Space VLBI observations of Pearson-Readhead survey sources

The VSOP Space VLBI mission uses the HALCA spacecraft, launched from Japan in February 1997, in conjunction with ground radio observatories around the world to create a high resolution radio-wavelength imaging facility. We are using this unique facility to observe a sub-sample of Pearson-Readhead Survey sources at 4.8 GHz to determine core brightness temperatures and pc-scale jet properties. We will highlight one of the sources that has been observed using a combination of the HALCA spacecraft and the EVN, 1642+690, and describe the preliminary brightness temperature distribution for the sub-sample, based on all data analyzed to date.     

Comparison of Internal Structures of Marine Manganese Deposits of Hydrogenetic, Diagenetic and Hydrothermal Origins

Abstract: Detailed microscopic observation, combined with X-ray diffraction and EPMA analyses of samples from marine manganese deposits of three different origins, suggests that characteristic internal structures are inherent in each manganse mineral; vernadite (δ–MnO₂), buserite (10Å–manganate) and todorokite (10Å–manganate).     

湖南长城岭-凤凰山地区遥感蚀变信息提取与成矿预测

长城岭-凤凰山地区位于湘南多金属矿集区,找矿前景较好.通过Landsat-8遥感影像解译长城岭-凤凰山一带的线-环结构,发现长城岭"Φ"型构造特征;根据实测围岩蚀变光谱特征,选用主成分分析法和比值+主成分分析法,基于landsat-8 OLI数据提取了长城岭-凤凰山地区铁染、羟基及硅化蚀变异常信息,基于Worldvie...     

岩溶区地下水数值模拟研究进展

岩溶含水介质的不均一性导致岩溶地下水流动、溶质运移和热量迁移的数学模拟研究成为地下水模拟的难点。本文综述了岩溶区地下水流模拟的几种方法,重点阐述了等效多孔介质法、双重连续介质法和三重介质法的定义、发展过程和适用范围,并回顾了这几种方法的研究成果。从等效多孔介质法到三重介质法,模拟精度不断提高,适用范围也逐渐由大区域实际问题向小区域理论研究过渡。介绍了溶质运移模拟和热迁移模拟的研究方法及实例。溶质运移模拟以对流弥散方程为基础,其中尺度效应是溶质运移模拟的重点研究问题;热量迁移模拟应考虑地下热水密度变化对地下热水运动的影响。溶质运移模拟和热量迁移模拟往往是将迁移模型和已经调试成功的地下水流动模型相耦合,从而达到模拟溶质及热量迁移的目的。由于溶质运移和热量迁移的复杂性,现阶段水流模型多数处于等效多孔介质模型阶段。综合理论及实际应用,指出精确刻画裂隙及管道和注重基础数学算法是岩溶水数值模拟进步的关键。      

A pre-Ipswichian cold stage mammalian fauna from the Balderton Sand and Gravel,Lincolnshire, England

The Balderton Sand and Gravel has yielded one of very few mammalian faunas dated to the penultimate Cold Stage in Britain. The assemblage is dominated by mammoth and woolly rhinoceros, with subordinate horse, red deer, bison, straight-tusked elephant, musk ox, reindeer, wolf, lion, brown bear and cf. narrow-nosed rhinoceros. This fauna indicates cold stage conditions, probably including one or more interstadial episodes. The presence of straight-tusked elephant and cf. narrow-nosed rhinoceros supports its pre-Devensian age, and provides corroboration for the occurrence of these taxa in the British Wolstonian. An attempt is made to analyse the fossil collection by preservation type and adhering sediment: the occurrence of individual species appears to be largely uncorrelated with lithology. The Balderton assemblage corresponds well to other British mammal faunas assigned to a cold interval between the Hoxnian and Ipswichian Interglacials.     

Differential thermal stresses in the Earth

Summary. Rocks have a significant thermal expansion coefficient and a high modulus of elasticity. Small thermal changes can therefore generate very substantial stresses. A convenient idealized example is the mechanically free, cooling thermal boundary layer in a material that suddenly turns from plastic to rigid in cooling through a 'rigidus' temperature. This simplified case can be solved analytically for both a linear and an error function temperature profile. A compressed layer develops near the surface, with a logarithmic singularity of stress at the boundary. At a depth of 0.2 of the elastic thickness, the stress changes to tensile, and peaks at 15 per cent of the confined shrinkage stress in the middle of the rigid layer. The situation is similar to the stresses in one half of a piece of tempered glass. Like the tempered glass, both the cooling lithosphere and a plated boundary to a magma chamber are subject to breakage when cracks are induced in the tensile layer. Positive pore (magma) pressure is required to overcome confining pressure at depth in the lithosphere, but cracking could become catastrophic in the plated boundary to a near-surface magma chamber.     

The tectonic significance of a porphyroblastic blueschist facies overprint during Alpine orogenesis: Sifnos, Aegean Sea, Greece

The MacArgon program^∗ has been used to model published apparent age spectra for white micas from the island of Sifnos, Cyclades, Greece. These micas formed during a period of porphyroblastic mineral growth (M₂) in the epidote-blueschist facies, at > ~ 460 °C and < ~ 14 kbar. M₂ marked the onset of a major period of deformation (D₃) during which kilometre-scale ductile shear zones formed and widespread recumbent folding took place. The modelling experiments suggest that flat apparent age spectra observed in the eclogite-blueschist domain (EBD) can only be obtained if the rocks cooled rapidly below ~ 350 °C after M₂ at ~ 42 Ma. Cooling rates must be > 50 °C/m.y., and since M₂ is followed by D₃ we infer that these are the cooling rates during D₃. Modelling experiments for micas from the greenschist domain (GSD) structurally underneath the EBD suggest that the GSD cooled rapidly, but at ~ 32 Ma. One tectonic model that might explain the rapidity of cooling rates inferred for the EBD model supposes that ambient temperatures were at ~ 500 °C when M₂ took place, but thereafter the high pressure rocks were thrust to the north and rapidly cooled as the result of their juxtaposition against cooler, shallower levels of the crust.