EFFECTS OF EXISTENCE OF SEDIMENT PARTICLES ON THE ENERGY LOSS OF FLOW

ＥＦＦＥＣＴＯＦＥＸＩＳＴＥＮＣＥＯＦＳＥＤＩＭＥＮＴＰＡＲＴＩＣＬＥＳＯＮＴＨＥＥＮＥＲＧＹＬＯＳＳＯＦＦＬＯＷ￥ＬＩＵＱｉｎｇｑｕａｎ;ＣＨＥＮＬｉａｎｄＬＩＵＤａｙｏｕ（Ａｓｓｏｃ．ＲｅｓｅａｒｃｈＦｅｌｌｏｗ,ＩｎｓｔｉｔｕｔｅｏｆＭｅｃｈａ...     

青藏高原东北部地壳浅部块体物质运动的基本特征及其与南北地震带(北段)关系之研究

本文根据青藏高原东北部震源深度、震源机制及其周边断裂晚更新世晚期以来的运动特征等大量资料分析,讨论了本区地壳浅部块体物质运动的基本特征、西秦岭北缘断裂带构造地貌滞后效应现象及其原因,同时探讨了大闸口内强震成因,成带等问题。     

HORIZONTAL MOVEMENT CHARACTERISTICS OF THE ACTIVE SANWEISHAN FAULT AND ITS MECHANISM: CONSTRAINTS ON THE GROWTH OF THE NORTHERN QINGHAI-TIBETAN PLATEAU

The northern margin of the Qinghai-Tibet Plateau is currently the leading edge of uplift and expansion of the plateau. Over the years, a lot of research has been carried out on the deformation and evolution of the northeastern margin of the Qinghai-Tibet Plateau, and many ideas have been put forward, but there are also many disputes. The Altyn Tagh Fault constitutes the northern boundary of the Qinghai-Tibet Plateau, and there are two active faults on the north side of the Altyn Tagh Fault, named Sanweishan Fault with NEE strike and Nanjieshan Fault with EW strike. Especially, studies on the geometric and kinematic parameters of Sanweishan Fault since the Late Quaternary, which is nearly parallel with the Altyn Tagn Fault, are of great significance for understanding the deformation transfer and distribution in the northwestward extension of the Qinghai-Tibet Plateau. Therefore, interpretation of the fault landforms and statistical analysis of the horizontal displacement on the Sanweishan Fault and its newly discovered western extension are carried out in this paper. We believe that the Sanweishan Fault is an important branch of the eastern section of the Altyn Tagh fault zone. It is located at the front edge of the northwestern Qinghai-Tibet Plateau and is a left-lateral strike-slip and thrust active fault. Based on the interpretation of satellite imagery and microgeomorphology field investigation of Sanweishan main fault and its western segments, it's been found that the Sanweishan main fault constitutes the contact boundary between the Sanweishan Mountain and the alluvial fans. In the bedrock interior and on the north side of the Mogao Grottoes, there are also some branch faults distributed nearly parallel to the main fault. The main fault is about 150km long, striking 65°, mainly dipping SE with dip angles from 50° to 70°. The main fault can be divided into three segments in the spatial geometric distribution:the western segment(Xizhuigou-Dongshuigou, I), which is about 35km long, the middle segment(Dongshuigou-Shigongkouzi, Ⅱ), about 65km long, and the east segment(Shigongkouzi-Shuangta, Ⅲ), about 50km long. The above three segments are arranged in the left or right stepovers. In the west of Mingshashan, it's been found that the fault scarps are distributed near Danghe Reservoir and Yangguan Town in the west of Minshashan Mountain, and we thought those scarps are the westward extension of the main Sanweishan Fault. Along the main fault and its western extension, the different levels of water system(including gullies and rills)and ridges have been offset synchronously, forming a series of fault micro-geomorphology. The scale of the offset water system is proportional to the horizontal displacement. The frequency statistical analysis of the horizontal displacement shows that the displacement has obvious grouping characteristics, which are divided into 6 groups, and the corresponding peaks are 3.4m, 6.7m, 11.4m, 15m, 22m and 26m, respectively. Among them, 3.4m represents the coseismic displacement of the latest ancient earthquake event, and the larger displacement peak represents the accumulation of coseismic displacements of multi-paleoearthquake events. This kind of displacement characterized by approximately equal interval increase indicates that the Sanweishan Fault has experienced multiple characteristic earthquakes since the Late Quaternary and has the possibility of occurrence of earthquakes greater than magnitude 7. The distribution of displacement and structural transformation of the end of the fault indicate that Sanweishan Fault is an "Altyn Tagh Fault"in its infancy. The activities of Sanweishan Fault and its accompanying mountain uplift are the result of the transpression of the northern margin of the Qinghai-Tibet Plateau, representing one of the growth patterns of the northern margin of the plateau.     

里海沿岸地壳和上地幔弹性参数的3D模型分析

为了解决应力和应变三维模拟问题,研讨了建立里海沿岸地壳和上地幔弹性参数信息数据库的结果及里海沿岸盆地的地球动力学模型。创建了研究区资料信息数据库,得到了研制地壳应力应变状态的计算法。     

地震与活动断裂空间关系的三维可视化建模

在回顾国内学者利用2D GIS空间分析功能研究地震与活动断裂关系的基础上,认为利用3D GIS更能准确地分析地震与活动断裂之间的三维空间关系.采用中国地震活动断层探测技术系统设计的数据结构,在ArcGIS下构建了三维断层模型,尝试性地提出了基于三维断层模型的三维空间缓冲区模型;并利用向量判别法实现了三维缓冲区的空间分析,进而实现了地震与活动断裂三维空间关系的分析方法,基于该模型对太原市区内主要断裂与地震的空间分布关系进行了初步定量分析研究.     

利用共轭梯度方法的电阻率三维反演若干问题研究

利用共轭梯度方法的电阻率三维反演是近几年才发展起来的 ,尚有诸多问题有待探讨。主要讨论了拉格朗日因子λ、共轭梯度迭代次数对三维反演结果的影响 ,以便获得良好的三维反演效果     

ArcGIS三维可视技术在山区水库库盘选址中的应用

介绍了利用ArcGIS系统的三维分析模块实现山区水库项目选址的三维可视化。基于GIS、航测、水工设计等基础资料,通过多个软件工具处理数据,在ArcGIS系统下整合与分析。最终实现了库区的三维地形漫游、水库蓄水、淹没等三维动态过程,为论证工程规模与工程选址提供决策依据。     

海原断裂高湾子地点三维探槽的开挖与古地震研究

对海原断裂高湾子地点进行大比例尺地质地貌填图和三维探槽开挖，揭示出７次古地震事件，除１９２０年地震外，它们的年龄分别为距今（１０００４±３１９６），（６６８９±１６９），（６１２０±５０５），（４２０８±５７７），（２７６３±３７２）和（１００５±４６５）ａ；重复间隔分别为（３３１５±３２００），（５６１±５３２），（１９２０±７６６），（１４２５±６８６），（１５７８±５９５）和（９８０±４６５）ａ。事件Ⅲ，Ⅳ，Ⅴ，Ⅵ，Ⅶ的水平位移量分别为（５．６±２．３），（１．５±１．１），（１．５±１．１），（２±１）和（７±０．５）ｍ。显示出重复间隔时间的分段性和特征行为的分级性。两次类似１９２０年强度的地震间隔期间，有３次位移量为１～２ｍ的地震发生     

NUMERICAL STUDY ON THE MIXING OF UNSORTED SEDIMENT PARTICLES DISCHARGED INTO A CROSS-FLOW BY MULTIPHASE PARTICLE-IN-CELL （MP-PIC） METHOD

The mixing characteristics of dredged sediments of variable size discharged into cross-flow are studied by an Eulerian-Lagrangian method. A three-dimensional (3D) numerical model has been developed by using the modified k-ε parameterization for the turbulence in fluid phase/water and a Lagrangian method for the solid phase/sediments. In the model the wake turbulence induced by sediments has been included as additional source and sink terms in the k-ε model; and the trajectories of the sediments are tracked by the Lagrangian method in which the sediment drift velocities in cross-flow are computed by a multiphase particle-in-cell (MP-PIC) method and the diffusion process is approximated by a random walk model. The hydrodynamic behavior of dumped sediment cloud is governed by the total buoyancy on the cloud, the drag force on each particle and velocity of cross-flow. The cross-flow destroys more or less the double vortices occurred in stagnant ambience and dominates the longitudinal movement of sediment cloud. The computed results suggest satisfactory agreement by comparison with the experimental results of laboratory.     

APPLICATION OF 3D HIGH PRECISION GRAVITY METHOD TO THE EXPLORATION OF DEEP BURIED HILL

Due to the influence of volcanic rock or weathering crust coverage, the quality of deep seismic data is often not reliable and it is difficult to identify small deep buried hill structure beneath the cover. However, the gravity exploration technology can use the remarkable density differences between the object and the overlying strata to identify this special geological reservoir. Although recently several rounds of seismic exploration have been carried out in Raoyang depression, Huabei Oilfield, North China to determine the existence of Hu 8 north deep buried hill, whether the buried hill really exists or not as well as its scale is still in controversial. In this paper, based on the information of seismic data and formation density, deep processing of 3D high precision ground gravity data has been carried out for 3D forward and inversion computation. The dimensional gravity forward calculation results show that the density of the deep anomaly body forms a relatively low gravity anomaly in the earth's surface. By using the potential processing method of vertical second derivative, and sliding filtering, the residual anomaly is separated from regional or background field, which illustrates the existence of a local high gravity anomaly at Hu 8 north area. According to the amplitude of residual gravity anomaly and formation density difference modeling, through a number of 3D forward calculations and 3D inversion of gravity data, the existence of Hu 8 north buried hill and its possible scale are basically determined. The results prove that the 3D high precision gravity method is effective in determining the deep buried hill structure in case that seismic data is not reliable.     

北祁连-河西走廊地区垂直形变与构造应力场关系的初步研究--三维有限元拟合结果分析

根据已知的地震地质资料对北祁连 -河西走廊及相邻区进行了三维有限单元剖分 ,在线弹性条件下 ,拟合了其 2 0a来垂直运动的总体趋势。计算表明 ,北祁连 -河西走廊地区垂直形变的拟合结果 ,与背景应力场的约束形式和变化特征密切相关 ,其中采用构造应力场增强作为加载条件以及稳定地块作为位移约束条件得出的拟合结果与该区域 2 0a来垂直运动的整体分布特点相一致。在此基础上 ,进一步得到其背景应力场增强的量值估算 ,其中SN方向的压力变化为 +0 .11MPa(压为正 ) ,EW方向的压力变化为 +0 .0 4MPa(压为正 ) ,EW方向的压力变化量是SN方向的 3倍左右。此外 ,根据计算得到的 10～ 15km深处剪应力增量Δγxy的分布情况 ,对比中强地震震源分布可以看出 ,剪应力增量与震源在空间分布上有一定的关联性。震源往往分布在剪应力增量变化较剧烈处 ,从而证实了拟合得出的构造应力场具有一定的合理性     

APPLYING 3D INVERSION OF SINGLE-PROFILE MAGNETOTELLURIC DATA TO IDENTIFY THE SHADE AND YUNONGXI FAULTS

Many synthetic model studies suggested that the best way to obtain good 3D interpretation results is to distribute the MT sites at a 2D grid array with regular site spacing over the target area. However, MT 3D inversion was very difficult about 10 years ago. A lot of MT data were collected along one profile and then interpreted with 2D inversion. How to apply the state-of-the-art 3D inversion technique to interpret the accumulated mass MT profiles data is an important topic. Some studies on 3D inversion of measured MT profile data suggested that 2D inversions usually had higher resolution for the subsurface than 3D inversions. Meanwhile, they often made their interpretation based on 2D inversion results, and 3D inversion results were only used to evaluate whether the overall resistivity structures were correct. Some researchers thought that 3D inversions could not resolute the local structure well, while 2D inversion results could agree with the surface geologic features much well and interpret the geologic structures easily. But in the present paper, we find that the result of 3D inversion is better than that of 2D inversion in identifying the location of the two local faults, the Shade Fault(SDF)and the Yunongxi Fault(YNXF), and the deep structures. In this paper, we first studied the electrical structure of SDF and YNXF based on a measured magnetotelluric(MT) profile data. Besides, from the point of identifying active faults, we compared the capacity of identifying deep existing faults between 2D inversion models and 3D models with different inversion parameters. The results show that both 2D and 3D inversion of the single-profile data could obtain reasonable and reliable electrical structures on a regional scale. Combining 2D and 3D models, and according to our present data, we find that both SDF and YNXF probably have cut completely the high resistivity layer in the upper crust and extended to the high conductivity layer in the middle crust. In terms of the deep geometry of the faults, at the profile's location, the SDF dips nearly vertically or dips southeast with high dip angle, and the YNXF dips southeast at depth. In addition, according to the results from our measured MT profile, we find that the 3D inversion of single-profile MT data has the capacity of identifying the location and deep geometry of local faults under present computing ability. Finally, this research suggests that appropriate cell size and reasonable smoothing parameters are important factors for the 3D inversion of single-profile MT data, more specifically, too coarse meshes or too large smoothing parameters on horizontal direction of 3D inversion may result in low resolution of 3D inversions that cannot identify the structure of faults. While, for vertical mesh size and data error thresholds, they have limited effect on identifying shallow tectonics as long as their changes are within a reasonable range. 3D inversion results also indicate that, to some extent, adding tippers to the 3D inversion of a MT profile can improve the model's constraint on the deep geometry of the outcropped faults.     

辽宁及邻区地壳构造应力场及其与地震活动关系的三维有限元数值模拟研究

依据最新的辽宁及其邻近地区地壳上地幔三维地震波速结构，并考虑地质构造、断裂以及地壳深部的构造环境等因素，建立研究区的三维地质模型；结合震源机制解与原地应力测量资料，分析区域现代地应力场特征，确定了研究区的边界约束和动力边界条件．在以上基础上，采用线弹性介质模型进行研究区三维构造应力场的有限元数值模拟，探讨研究区地壳应力场的基本特征．对比分析表明，本区地壳内应力场的三维有限元数值模拟结果与已发生的地震有着较好的对应关系，并指出了值得注意的有潜在发震可能的地震危险区．      

通过InSAR与GPS数据融合获取汶川地震同震三维形变场

针对In SAR与GPS两类独立的观测数据,利用广义测量平差理论中方差分量估计法,合理分配权重,有效地融合了这两类观测数据,从而估算出了地表在三维方向上的形变场。以四川汶川地震为例,利用In SAR干涉测量结果和一定数量的GPS观测值,通过该方法获取了地震断层两侧高相干区域上三维形变场,清晰地显示了汶川地震的逆冲和右旋走滑分量的位置分布整体特征。结果表明,在EW、SN和UD方向上地表形变量与GPS结果能够很好地吻合,融合结果在三维方向上的均方根误差均不超过5cm,证明了该方法能够得到精度较高的地震同震三维形变场,也揭示了利用方差分量估计法对相互独立数据之间有效融合的可行性。