数字地球及其对地震科学的影响

本文综述和探讨了数字地球概念的起源、内涵及其相关的关键技术,以及数字地球对地震科学发展的作用和影响。     

Shear-tensile crack as a tool for reliable estimates of the non-double-couple mechanism: West Bohemia-Vogtland earthquake 1997 swarm

Shear-tensile crack is a model for an earthquake mechanism that is more constrained than the moment tensor but that can still describe a non-shear focus. As such, the shear-tensile crack model is more robust than the moment tensor model and yields more reliable estimates for the earthquake mechanism. Such an advantage verifies the credibility of the non-double-couple component found for some events of the 1997 West Bohemia-Vogtland earthquake swarm. As expected, in several cases, a significantly resolved non-double-couple component was obtained where the moment tensor approach failed. Additionally, for non-shear sources, the shear-tensile crack model offers optimization of the Poisson number within the focus, concurrently with retrieval of the mechanism. However, results obtained for the joint inversion of the 1997 swarm indicate that resolution is low. A series of synthetic experiments indicated that limited observations during 1997 were not the cause. Rather, hypothetical experiments of both very good and extremely poor network configurations similarly yielded a low resolution for the Poisson number. Applying this method to data for recent swarms is irrelevant because the small non-double-couple components detected within the inversion are spurious and, thus, the events are pure double-couple phenomena.     

山东埠后古火山机构显微构造研究

埠后古火山机构由早白垩世陆相火山岩和次火山岩组成,铅、锌、铜、硫矿与后者有关。为了圈定火山通道的大致位置,在熔岩中采制定向切片,进行显微构造分析。通过变形、压密、阻挡、涡流等显微构造标志确定流动方位;利用长条状晶体的长轴方向确定流动线理。根据流动方位和流动线理圈出古火山口位置,进而指出在环火山颈的大断裂一侧,可能具区域找矿前景。     

基于Google Earth的气象多参数综合显示系统

利用Google Earth平台,将天气过程中的雷电、红外云图、MICAPS高空图以及TMPA降水资料,通过编写KML/KMZ文件,建立了气象多参数综合显示系统。该系统平台的建立,可在三维空间中真实动态地再现天气的发生发展及演变过程。此平台将有利于灾害性天气成灾过程和物理机制的研究。     

Evaluation of active and passive seismic earth pressures considering internal friction and cohesion

The Log-Spiral-Rankine (LSR) model, which is a generalized formulation for assessing the active and passive seismic earth pressures considering the internal friction and cohesion of backfill soil, is reviewed and improved in this study. System inconsistencies in the LSR model are identified, which result from an inaccurate assumption on the vertical normal stress field (σ_z=γz) in a general c–ϕ soil medium, and from omitting the effect of soil cohesion when solving for the stress states along the failure surface. The remedies to the said inconsistencies are presented, and local and global iteration schemes are introduced to solve the resulting highly coupled multivariate nonlinear system of equations. The modified LSR model provides a more complete and accurate solution for earth retaining systems, including the geometry of the mobilized soil body, the stress state along the failure surface, as well as the magnitude and the point of application of the resultant earth thrust.     

关于气候系统与地球系统的若干思考

分析了地球系统的基本特征和地球系统的能源和运转方式,指出地热涡和地冷涡是地面气候系统的重要成员. 利用全球地磁场资料,研究了地球内部焦耳热的分布和演变规律,结果表明:全球地磁场的变化与全球气温的变化有密切联系,而且焦耳热场的分布与地热带、火山分布、全球最大降水量带有很好的对应. 因此,要对气候变化有一个全面的认识,必须研究整个地球系统.     

Prediction of application scope of vertical fracture strike based on scattered wave fracture orientation function

Fracture system plays a very important role in the enrichment and accumulation of oil and gas in the reservoirs. Based on scattering wave information,Fracture Orientation Function( FOF) was built,which can be used to predict the fracture orientations. However,this method has only been verified by physical experiments without studies on the application scope. In this study,based on the linear sliding theory,FOF of the scattering wave was applied to the numerical simulation and the application scope was further studied according to fracture flexibility tensor. According to the fractures filled with gas and liquid,numerical simulation was conducted on the models with various fracture flexibilities. Numerical simulation results were used to inverse fracture orientation with the aid of the FOF of the scattering wave. The results show that it is workable to predict the vertical fracture orientation with the FOF of the scattering wave. Application of this method is more effective when the fractures are filled with gas than liquid. Moreover,the application scope can be predicted by the fracture flexibility.     

土工织物加筋体在提高路堤稳定性方面的应用

加筋技术在地基处理过程中的应用已经广泛应用,加筋作用原理、应力传递和加筋作用机理的研究与工程应用已经日趋成熟,就路基填筑的填筑材料特性、路基碾压施工特点及路基的断面形式,结合土工织物的筋材性状,对路基填筑中的加筋技术进行了设计与检算,并且提出了施工坡面防护措施。     

Barchan dune asymmetry: Observations from Mars and Earth

Barchan dune asymmetry refers to the extension of one barchan limb downwind. It is a common dune form on Earth and also occurs on Mars and Titan. A new classification of barchan limbs is presented where three types of limb morphology are identified: linear, kinked and beaded. These, along with other dune-scale morphological signatures, are used to identify three of the causes of barchan asymmetry on Mars: bi-directional winds, dune collision and the influence of inclined topography.The potential for specific dune asymmetric morphologies to indicate aspects of the formative wind regime on planetary surfaces is shown. For example, the placement of dune limbs can indicate the general direction and relative strength of formative oblique winds; an extreme barchan limb length may indicate a long duration oblique wind; a kinked limb may be evidence of the passage of a storm; beaded limbs may represent surface-wave instabilities caused by an increase in wind energy parallel to the dune. A preliminary application of these signatures finds evidence for bi-modal winds on Mars. However, these and other morphological signatures of wind direction and relative strength should be applied to planetary landforms with caution as more than one process (e.g., bi-modal winds and collision) may be operating together or sequentially on the dunefield. In addition, analysis should be undertaken at the dunefield scale and not on individual dunes. Finally, morphological data should be acquired from similar-scale dunes within a dunefield.In addition to bi-modal wind regimes on Mars, the frequent parallel alignment of the extended barchan limb to the dune suggests that dune collision is also an important cause of asymmetry on Mars. Some of the more complex dunefield patterns result from a combination of dune collision, limb extension and merging with downwind dunes.Dune asymmetric form does not inhibit dune migration in the Namib Desert or on Mars. Data from the Namib suggest that dune migration rates are similar for symmetric and asymmetric dunes. Further modeling and field studies are needed to refine our understanding of the potential range of limb and dune morphologies that can result from specific asymmetry causes.     

Assessing the power law hypothesis for the size-frequency distribution of terrestrial and martian dust devils

Competing hypotheses for the diameter dependence of terrestrial and martian dust devil frequency are assessed using new field observations from two sites in the southwestern United States. We show that at diameters less than 12 m, our observed dust devil size-frequency distributions are better fit by an exponential function than by a power law formulation, and discuss the implications for larger dust devils on Earth and Mars.