中天山骆驼沟火山岩的地球化学特征及其构造环境

中天山骆驼沟石炭纪火山岩系主要由枕状玄武岩，玄武岩和细碧岩构成，另有少量英安岩和流纹岩，其中基性火山 岩全岩化学成分CIPW计算结果主要含Di和Hy，少量含Ol和Qz，不含Ne，而且岩石的Ｎb/ Y比值均小于0．7，属亚碱性系列，在SiO2-FeO/MgO图中样品点落在拉斑玄武岩区域，岩石的TiO2含量较高（1．48－2．31），Th/Ta=1.34-2.06,La/Ta=12-17,Ti/V=37.16-51.49,La/Nb≈1,显示了MORB的特征，岩石εNd(t)值为＋3．80－＋6．53，并具高Nb含量和低的Zr/Nb比值（分别为10－22ug/g,6.8-10.3）以及富集轻稀土的特点，表明岩石兼具E－MORB与OIB的特征，是源于有富集地幔物质加入的亏损地幔源区，为MORB与EMII不同程度混合的产物，另外，岩石富含Ti,LILE,LREE,HFSE，具有较高的Ti/V,Zr/Y比值，较低的Zr/Nb,LREE?HREE比值和较低的Mg值（45－55），以及碱性岩不发育则显示了大陆溢流玄武岩（CFB）的特征，表明骆驼火山岩形成于大陆减薄拉张环境。     

银川隐伏断层钻孔联合剖面探测

为获取银川隐伏断层近地表断错、上断点埋深、最新活动时代及滑动速率等信息,在浅层地震勘探基础上,沿断层自北向南横跨主断层布施了新渠梢、满春和板桥3条钻孔联合剖面,确定了主断层在3条剖面上的准确位置,获得主断层上断点埋深分别为5·18~8·30m(新渠梢)、5·01~6·50m(满春)和10·0~13·59m(板桥)。结合测年数据分析:新渠梢剖面断层全新世活动,晚更新世末期以来滑动速率为0·14mm/a;满春剖面断层也是全新世活动,但晚更新世末期以来滑动速率为0·05mm/a;板桥剖面断层全新世不活动。综合地震勘探资料进一步分析认为,以银古路为界,目标区银川隐伏断层分南北2段:北段属全新世活动断层,且自北向南活动强度呈减弱趋势,南段属晚更新世末期活动断层;北段活动强度显著大于南段     

LSTM神经网络在地震资料初至拾取中的应用

本文引入RNN的升级算法LSTM神经网络技术,建立了一套海量数据、高精度的自动拾取地震资料初至流程。相比于其他神经网络方法,LSTM神经网络能够提取数据的时序特征,加强学习初至前噪音时序特征,从而提高初至拾取的精度,为地震资料的初至拾取提供一套新的思路。首先设计样本制作过程并建立、训练模型,通过模拟资料验证方法的有效性,应用于胜利油田浅海与西部山地地震勘探资料的初至拾取,取得理想效果,证明LSTM神经网络初至拾取具有较高的精度与适用性。     

A mesh-free particle model for simulation of mobile-bed dam break

Mesh-free particle (Lagrangian) methods such as Moving Particle Semi-Implicit (MPS) and Smoothed Particle Hydrodynamics (SPH) are the latest generation of methods in the field of computational fluid dynamics that attracts lots of attention in modeling applications where large interfacial deformations and fragmentations exist. Due to their mesh-free nature, these methods are capable of simulating any kind of boundary/interface deformation and fragmentations. This study aims to develop a new mesh-free particle model based on the weakly compressible MPS (WC-MPS) formulation for modeling of a dam break over a mobile bed, which is a highly erosive and transient flow problem. A multiphase model, capable of handling the density and viscosity discontinuity and in which the solid (sediment) phase is treated as a non-Newtonian fluid, is introduced. The resulting model is first validated using a two-phase dam break problem and is then applied to the mobile-bed dam break problem with different conditions, comparing the results to those obtained from some experimental works.     

Two-dimensional numerical modeling of dam-break flows over natural terrain using a central explicit scheme

A two-dimensional (2D) numerical model has been developed to solve shallow water equations for simulation of dam-break flows. The spatial derivatives are discretized using a well-balanced explicit central upwind conservative scheme. The scheme is Riemann solver free and guarantees the positivity of the flow depth over complex topography if the Courant number is kept less than 0.25. The time integration is performed by Euler’s scheme. The model is verified against analytical results for water surface elevation and discharge for three benchmark test cases. A good agreement between analytical solutions and computed results is observed. The property of well-balancing in still water over an uneven bottom is also confirmed. The model is then validated by simulating a laboratory experiment in which a dam break flow propagates over a triangular obstacle. The model performance was found to be satisfactory. A dam break laboratory experimental test case on a frictionless horizontal bottom is also simulated for 2D validation of the model, and good agreement between simulation and the experimental data is observed. The suitability of the proposed model for real life applications is demonstrated by simulating the Malpasset dam-break event, which occurred in 1959 in France. The computed arrival time of the flood wave front and the maximum flow depths at various observation points matched well with the measurements on a 1/400 scale physical model. The overall performance indicates that this model can be applied for simulation of dam-break waves in real life cases.     

A two dimensional hydrodynamic and sediment transport model for dam break based on finite volume method with quadtree grid

This study aims to develop a robust, accurate and computationally efficient hydrodynamic and sediment transport model for dam break flows. The two dimensional shallow water equations are resolved based on the finite volume method with an unstructured quadtree mesh. The sediment transport and bed evolution modules are coupled with hydrodynamic module to predict simultaneously the hydrodynamics, sediment concentrations and morphological changes. The interface flux is computed by the HLL approximate Riemann solver with second order accuracy. The effects of pressure and gravity are included in source term in this model, which can simplify the computation and eliminate numerical imbalance between source and flux terms. For dam break flows occurring in complicated geometries, the quadtree rectangular mesh is used to refine the interesting area and important part. The model is first verified against results from laboratory experiments, existing numerical models and real life case. It is then used to simulate dam break flows over a mobile bed to investigate the bed evolution. The results are compared with experimental data and field data with good agreement. The method is simple, efficient, and conservative. It shows promise for handling hydrodynamic simulation and sediment transport for a wide range of dam break flows.     

Topographic characteristics of laboratory induced shear fractures

The topography of laboratory induced shear fracture surfaces of Westerly granite was studied. Three types of fracture surfaces were examined: (1) a fresh fracture from the shear failure of an intact sample under polyaxial loading (₂ = 40 MPa > ₃ = 15 MPa); (2) a shear fracture subjected to frictional sliding of 100 m under polyaxial loading; (3) a shear fracture subjected to frictional sliding of 800 m under conventional triaxial loading (₁ > ₂ = ₃ = 40 MPa). Both sliding distances are within the range of the grain size of Westerly granite. The results are represented by a power spectral method.Similar to the power spectra from natural rock surfaces, the power spectra of the induced shear fracture surfaces fall off about 2 orders of magnitude per decade increase in spatial frequency. No corner frequency exists in the power spectra over a spatial frequency range from that corresponding to the profile length to the Nyquist frequency. A slope break in the power spectrum was identified, however. It separates a steeper low frequency segment from a less steep high frequency segment. The spatial frequency at the slope break corresponds to a wavelength of several hundred microns which is on the scale of the microcracking and contact breaking on the fractures. Upon re-examining power spectra of natural fault traces and fault surfaces obtained in previous studies, we noted similar slope breaks. We suggest that this slope break may have significant implications in the scaling problem. Both the induced fracture surfaces and natural faults exhibit topographic characteristics different from those of sawcut surfaces, which have been widely used in laboratory rock friction experiments. In the present study, we observed that even a small amount of sliding (less than a grain size) already results in significant mismatches between the paired sliding surfaces in the direction normal to sliding.     

井间地震初至波分析

在模拟对比不同模型条件下初至波的基础上,分析了造成初至不清晰两种可能的原因,一种是初至波为续至波所干扰,另一种初至波在垂直方向上的投影很小甚至为零。并指出可以综合利用水平分量和垂直分量记录来提高初至时间拾取的精度。     

Transport of suspended sediment under the dam‐break flow on an inclined plane bed of arbitrary slope

The problem of transport of suspended sediment after the break of a dam on an inclined bed is considered. To that end we use the shallow‐water approximation for arbitrary, constant slopes of the bottom, taking into consideration the effect of friction. The numerical technique and the frictional model are validated by comparison with available experimental data and asymptotic analytical solutions, with special attention to the numerical solution near the wetting front. The transport of suspended sediment down the inclined bed is obtained and discussed as a function of the slope of the bed for different values of the parameters characterizing the sediment and its transport properties. For sufficiently large times we always find the formation of roll waves near the water front, which affects the transport of sediments significantly. These strong oscillations are accurately computed with the numerical method used. The relative importance of the bed load (to the suspended load) sediment transport is also discussed as a function of the size of the sediment particles and the slope of the bed for different models on the initiation of sediment suspension from bed load. We also check the dilute sediment approach and characterize the conditions for its failure. Finally, the results of the present simplified model are intended to be used as tests of more complex numerical models. Copyright © 2007 John Wiley & Sons, Ltd.     

The application of integrated urban inundation model in Republic of Korea

In urban areas with a high building density, features such as roads, buildings and river dykes significantly affect flow dynamics and flood propagation. This should therefore be accounted for in the model set‐up. While 2D hydraulic models of densely urban areas are at the forefront of current research into flood inundation mechanisms, these models are constrained by inadequate parameters of topography and insufficient data. In order to solve these problems, topographic information obtained from digital elevation model (DEM) is directly programmed into the urban inundation model for a densely urban area, without exchanging the input data. In this paper, the extraction of building area is described using a tight coupling approach within a GIS environment, and its influence on the extent of flood inundation with a high building density is estimated. Copyright © 2009 John Wiley & Sons, Ltd.