Deep structural characteristics and seismogenesis of the M≥8.0 earthquakes in North China

Introduction North China is a seismically active area in the eastern part of China, where four M8.0 earthquakes have been recorded in the historical documents and confirmed by the researchers. The first is the M=8.0 earthquake occurred in A.D. 1303 in Hongtong, Shanxi Province. It was the ear-liest M=8.0 earthquake recorded in the historical document in China. The second is the M=8.0 earthquake occurred in A.D. 1556 in Huaxian County, Shaanxi Province. The other two are the M=8.5 earth…     

洛阳市水资源可持续开发利用对策研究

洛阳市是一个水资源总量偏少的地区。按可供水资源量、现状尚可维持．预计2005年和2010年全区将缺水0．75亿m^3／a和2．43亿m^3／a。为了保证洛阳市经济快速、持续的发展，水资源的可持续开发利用已成为关键性因素之一。对于本市来讲，依法治水、科学用水、节约用水、污水资源化是实现市域水资源开发利用和保护良性循环的重要举措，核心是抓好农业节水和城镇用水。本文对域内水资源可持续开发利用，进行了可行性研究。     

O(T2)精度下椭球界面Dirichlet边值问题的积分解

研究了边界是参考椭球面的Laplace方程Dirichlet边值问题的求解，在O(ε4·T)精 度下给出了参考椭球界面上扰动重力位Dirichlet外问题的积分解式. 该结果理论上优于目 前常用的球近似下的积分解式，从而为研究物理大地测量中边值问题的求解提供了新的依据     

Numerical Modeling of Water Wave Interaction with A Soft Mud Bed

A vertical 2-D numerical model is presented for simulating the interaction between water waves and a soft mud bed. Taking into aceotmt nonlinear theology, a semi-empirical theological model is applied to this water-mud model, reflecting the combined visco-elasto-plastic properties of soft mud under such oscillatory external forces as water waves. In order to increase the resolution of the flow in the neighborhood of both sides of the inter-surface, a logarithmic grid in the vertical direction is employed for numerical treatment. Model verifications are given through comparisons between the calculated and the measured mud mass transport velocities as well as wave height changes.     

Deep seismic sounding data reveal the crustal structures beneath Zoigê basin and its surrounding folded orogenic belts

Songpan-Garze massif is located at the turning position of tectonics from the nearly west-east direction to the nearly north-south direction in the northeastern margin of Tibetan Plateau,with Zoigê basin in the centre of the massif.In this paper,we build a crustal structure model of Zoigê basin and its surrounding folded orogenic belts using the deep seismic sounding data in this region.We also discuss structures and properties of the basement in Zoigê basin,tectonic relations between Zoigê upland basin and its surrounding folded orogenic belts,crustal deformation and thickening in the northeastern margin of Tibetan Plateau,and decoupling and relaxing processes in the crust.The results indicate that a special "Mesozoic basement" is formed of Triassic rocks with high density (2.65-2.75 g/cm3) and high velocity (5.6 km/s) in Zoigê basin.Songpan-Garze tectonic massif was transformed into two types of tectonic units with different crustal structures,i.e.,relatively stable Zoigê upland basin and active folded orogenic belts around the basin,in the course of the crustal material of Tibetan Plateau flowing eastward and obstructed by surrounding stable blocks.The thickening of the crust in the northeastern margin of Tibetan Plateau mainly occurred in the mid and lower crust,and the structure characterized by low velocities and multiple reflectors obviously appears in the folded orogenic belts around Zoigê basin.It implies that the mid and lower crust underwent a strong tectonic deformation in the folded orogenic areas.The thickness of the crust is about 50 km in Zoigê basin and the folded orogenic belts at the both southern and northern sides of Zoigê basin.The "Mountain root" cannot be identified.It is inferred that during the later orogenic period the eastwards flowing deep materials moved clockwise along the relatively relaxing southern side around the eastern tectonic knot under the obstructing of surrounding rigid massifs,and it resulted in the strong stretching action of the folded orogenic belts around Zoigê basin.     

Crustal structure of northeastern Tibetan plateau and Ordos block:Waveform interpretation of the Maqen-Jingbian seismic refraction profile

The Maqen-Jingbian wide-angle seismic reflection and refraction experiment was carried out in 1998,which aims at determining detailed structure in the crust and top of the upper mantle and understanding structural relation between the northeastern Tibetan plateau and the Ordos block. The 1-D crustal models inferred by waveform inversion show strong variations in crustal structure,which can be classified into four different types:1 an Ordos platform with the Proterozoic crust and two high-velocity layers in ...     

The Crust-Mantle Structure in Zhangbei-Shangyi Earthquake Area

The seismic data obtained from the wide angle reflection and refraction profiles that pass through Zhangjiakou area of Hebei Province were interpreted. Some conclusions drawn from the result are as follows: (1) The nearly EW-trending Zhangbei-Chongli crustal fault zone and WNW-trending Zhangjiakou-Bohai Sea deep crustal fault zone meet in the Zhangbei earthquake (Ms = 6.2) area; (2) At the intersection, the two deep crustal fault zones that stretch to the Moho and the discontinuities of interfaces within the crust form the path for large area basalt eruption in Hannuoba; (3) In the earthquake area, the local velocity reversal in the middle-upper crust and abnormal low velocity zone in the lower crust imply that the magmatic activity there is still fairly violent; and (4) The recent activity of Zhangjiakou-Bohai Sea deep crustal fault zone may be the main cause of the Zhangbei earthquake.     

持续发展的环境战略与地下水环境

面对地下水环境日益恶化的现状,必须高瞻远瞩,从持续发展的战略高度,立足于永续利用的观点,探讨如何为后代留下一个较好的赖以生存的地下水环境问题.为此,应对地下水环境的特点、演化、容量、负载等问题进行深入研究;在此基础上,对不同自然和经济区域地下水环境的脆弱程度作出论证和评价;在兼顾经济、社会、生态效益的基础上,提出地下水环境功能保护区划,作为地下水科学管理的依据.     

1947年青海达日7(3/4)级地震构造的遥感影像特征

通过对陆地卫星MSS磁带做不同计算处理表明:比值负变换—比值增强—彩色级上色所产生的图像对研究1947年青海达日7(3/4)级地震构造具有良好效果。不同时相陆地卫星影像均确定了该区北西西向线性构造的主导作用,同时计算结果明显地反映出达日县桑日麻盆地存在近东西向隐覆断裂;结合航磁资料分析,平顶山环形影象为一巨大隐伏岩浆岩体的反映,据此推断出达日地震构造及宏观震中位置,并得到实地考察的验证。     

固体潮对测站位移影响的理论研究

重新推导了IERS2 0 0 0中关于固体潮对测站位移影响的所有公式 ,指出 :在时间域内二阶和三阶引潮力位对测站位移影响的公式中 ,理论上应以测站地心距代替地球赤道半径。利用最新的精密引潮位展开代替IERS2 0 0 0采用的Cartwright&Tayler(1971)潮汐展开 ,重新计算了田谐潮波和带谐潮波的相对频率特性的改正。计算表明 ,以上两种修正在亚毫米量级上与IERS2 0 0 0存在差异 ,这在目前的空间大地测量技术中是必须考虑的。