1969年渤海7．4级地震区地质构造和发震构造的初步研究

根据石油地质勘探资料和地震学等研究的成果,对1969年渤海7.4级地震的构造条件作了具体而较深入的分析,填补了华北渤海大震区地震构造研究的空白.震区位于渤海湾新生代裂陷盆地的东部,地处北北东向营潍断裂带与北西向北京-蓬莱断裂带交汇的地区.早第三纪断陷阶段,该区于地壳上部主要发育北北东、北西和东西向3组断裂,呈铲状和平面状形态,正断性质,多属断陷主断裂.晚第三纪以来的拗陷阶段,先存断裂有不同程度的活动;同时还新发育一条北东向黄河口-庙西北断裂带.7.4级地震的震源断层走向为北东45°,倾向南东,近于直立,呈右旋走滑性质,埋藏于15～34km的深度范围.大震的发震断裂不是营潍断裂带,而是黄河口-庙西北新生断裂带.     

营口潍坊断裂带新生代活动的特征

营潍断裂带以北西向北京 蓬莱断裂带与之交汇的部位为界分南北两段,北段由辫状交织的两条断裂组成;南段为并列的东西两支断裂,但被黄北、莱北和潍北等北东东向断裂横切成4节。断裂带北段早第三纪水平拉张和垂直差异活动强烈,控制了断陷盆地的发育,晚第三纪—第四纪右旋走滑活动显著。南段本身活动甚弱,但黄北等横向断裂早第三纪水平拉张和垂直差异活动强烈,相应形成了黄北等几个断陷盆地;晚第三纪—第四纪横向断裂仍有活动。断裂带活动具明显的分段性,南段是受横向断裂强烈分割、改造而被“废弃”的一段。断裂带新生代活动具由南部和北部统一向中部迁移的特点,北段还有向东侧迁移的趋势。断裂带地震活动微弱,渤海中部斜穿断裂带分布的北东向地震带,可能是黄河口聊城新生地震构造带向海区延伸的部分     

基于GPS资料分析银川盆地地壳运动特征

利用银川盆地及周边地区1999—2007年的GPS数据,研究了该区域现今地壳水平速度场特征,根据区域地壳主应变率、面膨胀率及最大剪应变率的空间变化以及小震分布特征,结合该地区的地质构造背景,对黄河断裂的南北段差异特征及盆地构造动力和地震危险性分析研究,结果表明:研究区内GPS测站主要运移方向为E-SE向。贺兰山东麓断裂和黄河断裂北段以拉张兼走滑运动为主,而黄河断裂南段以走滑运动为主,盆地整体处于剪切拉分断陷环境;银川盆地比周围块体的主应变率大,最大主应变方向为NW向,以张应变为主,结合面膨胀率和最大剪应变率也都显示盆地内存在较强的拉张和剪切变形,盆地内地震主要分布在南部地区;主应变率、面膨胀率、最大剪应变率和小震活动性均说明黄河断裂南段比北段活动性强;银川盆地地壳变形程度高,而周边稳定块体变形弱,黄河断裂和贺兰山东麓断裂分别位于应变强弱变化的东、西边界上,断裂具有较强的应变积累,表现出较高程度的地震危险性。     

山西断陷带地震活动的新构造背景

鄂尔多斯块体东缘的山西断陷带,是块体周缘形成最晚、地震活动强度最大,频度最高的断陷带.地震活动与控制断陷盆地的主干断裂、盆地的沉降中心、盆地的发育历史、盆地新构造的复杂程度、盆地的北北东走向段等密切相关.盆地间与盆地内的北西向断裂对地震活动也有一定的控制作用.文章还讨论了断陷盆地是一种地震构造类型及晋陕断陷带等问题.     

山西地堑系的现代构造活动特征

山西地堑系近二十多年来地壳垂直活动较为强烈,山区上升幅度为30—50毫米,盆地下降幅度为20—40毫米。主要断裂垂直位移速率小于1毫米/年,有些断裂水平位移速率约1.5—2.0毫米/年。本区现代构造活动,主要受北东—北东东向挤压作用,致使地堑系出现了北北东向不连续的剪切破裂带,两侧块体作相对右旋扭动,再加上北西向的拉张作用,区内形成了一系列的断陷盆地。     

张家口-蓬莱断裂带地震构造特征的初步探讨

北西向张家口－蓬莱断裂带由近２０条北西至北西西向断裂组成,是一条对新生代区域地质构造发育起到重要控制作用的地壳构造带。断裂带新生代活动由中部向西北和东南部发展,总体表现左旋走滑性质。断裂带有山西断陷盆地带等几条北东向活动构造带与之交汇,形成北西和北东向两组断裂相互交切的构造组合,出现５个复杂的构造交接段。６级以上强震和大多数中小地震群集于这些地段,其中北西和北东向断裂都可能发生地震,显示共轭破裂错动特征,但北东向断裂发生的地震强度较大。张北－尚义６．２级地震发生于断裂带与山西断陷盆地带交接段的西缘,是断裂带向西北扩展的结果     

兰州-民和断陷盆地地热地质条件分析及热储概念模型

研究了兰州—民和盆地的地热地质条件，认为盆地位于中祁连隆起带的东段，为地壳厚度陡变带部位，发育的NWW向和NNW向深大断裂成为深部热源的上升通道并控制地温分布．导热断裂与低热导率岩层组合容易形成地热异常，形成层状热储和带状热储．均为低温地热资源．提出该断陷盆地的热储概念模型是地壳深部供热—深大断裂导热—低热导率岩层聚热一侧向地下径流补水．     

1966年邢台7.2级地震的构造背景和发震构造

本文根据石油地质勘探的最新资料和元-济人工地震地壳测深剖面相应地段重新解释的结果,分析了邢台7.2级地震的构造背景和发震断裂。研究结果表明,7.2级地震震中位于束鹿断陷盆地南部次凹的东缘,该次凹发育在由新河断裂等4条缓倾铲形正断裂分制围限地台盖层而成的“斛”状构造块体上,块体之下的地壳中存在两条倾向相反的高角度断裂;地震与断陷主断裂及其控制的断陷盆地并非是简单的对应关系,7.2级地震的发震断裂不是单一的缓倾铲形新河断裂或其下方的高角度的F_3断裂和深部的东断裂,而是它们的组合,且高角度断裂是发震断裂的主要部分     

渤海盆地现代构造应力场与强震活动

渤海位于北华北新生代裂陷盆地的东部，是一个晚第四纪形成的内陆海盆. 渤海盆地活动断裂发育，地震活动强烈，交会于渤海中部的NE向营口——潍坊断裂带北段、庙西北——黄河口——临邑断裂带及NW向北京——蓬莱断裂带是主要的活动构造带，将海区分成4个次级新构造区，成为现代应力场作用的构造基础. 综合研究38个震源机制解和75个井区应力场等资料，以及构造应力场二维数值模拟计算结果表明，渤海及其邻区现代构造应力场的压应力方向为NE60～90，张应力为SN——NW30；以水平和近水平应力作用为主；不同构造区主应力方向存在一定的差异. 现今渤海地区地壳发育以NNE——NE和NW——WNW走向的共轭剪切破裂为特征，是控制地震活动的主要构造.      

江汉盆地构造模式和演化及其与中强地震关系研究

本文通过对江汉盆地地震物探的剖析,结合该地区大地构造环境特点,指出盆地主要有三个发展阶段组成:前陆盆地阶段(中三叠-晚侏罗纪),主要受秦岭大别逆冲推覆,前缘挠曲形成前陆盆地,同期形成NW向和NEE-EW向两组断裂,从而奠定了盆地棋盘格网构造体系;断陷盆地阶段(白垩纪-老第三纪),断裂由原逆冲或逆走滑转变为正断性质,且控制盆地沉积中心,同时盆地发生顺时针旋转,岩浆活动强烈;新第三纪以来盆地阶段,盆地以坳陷为主,整体下降,表现为断裂对盆地沉积控制明显减弱,岩浆活动停止. 根据石油物探剖面建立了盆地的构造格架,即盆地内两组断裂及其形成的狭窄低凸起/地垒条带将盆地分为4个NNW向展布和3个NEE向展布凹陷带. 盆地地壳结构和小震分布及震源机制解显示地震集中在沉降最大的潜江-沔阳凹陷带附近,震源深度优势分布在15 km左右,即盆地基底附近.     

INTERNATIONAL RESEARCH AND TRAINING CENTER ON EROSION AND SEDIMENTATION(IRTCES)

正Director:Shangfu Kuang,China Vice-directors:Chunhong Hu,China Duihu Ning,China Guangquan Liu,China The International Research and Training Center on Erosion and Sedimentation(IRTCES)was jointly set up by the Government of China and UNESCO on July 21,1984.It aims at the promotion of international exchange of knowledge and cooperation in the studies of erosion and     

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Information for authors

正SCIENCE CHINA Earth Sciences,an academic journal cosponsored by the Chinese Academy of Sciences and the National Natural Science Foundation of China,and published by Science China Press and Springer,is committed to publishing high-quality,original results in both basic and applied research.     

Dynamic process-response model of river channel development

Feedback mechanisms, which operate upstream through drawdown and backwater effects and downstream through sediment discharge are responsible for channel evolution. By combining these mechanisms with channel processes it euables a dynamic process-response model to be developed to simulate the initial evolution of straight gravel-bed channels. When erosion commences on a land surface, sediment entrained in the headwater reach by hydraulic action is selectively transported, deposited and reworked. This produces a damped oscillation between degradation and aggradation as the channel and valley respond to spatial and temporal variations in sediment calibre and hydraulic conditions. The initial cut and fill phases are responsible for valley incision and floodplain development while secondary and subsequent activity can produce river terraces. Eventually sediment entrainment in the headwaters declines as slopes are reduced. Subsequent channel evolution is relatively insignificant because it is dependent on local weathering activity producing material that can be transported on declining slopes. Therefore landforms produced during the initial phase of development, when local weathering was non-limiting, dominate the landscape.     

Discussion on the Precise Relocation and Seismo-Tectonics of the Jiujiang-Ruichang Earthquake

Based on relocating the Jiujiang-Ruichang earthquake sequence which occurred on November 26, 2005 in Jiangxi Province with the double-difference （DD） algorithm and master event technique, the paper discusses the focal mechanism of the main shock （MsS.7） and the probable seismo-tectonics. The precise relocation results indicate that the average horizontal error is 0.31kin in a EW direction and 0.40kin in a NS direction, and the average depth error is 0.48kin. The focal depths vary from 8kin to 14kin, with the predominant distribution at 10kin - 12kin. The epicenter of the main shock is relocated to be 29.69^oN, 115.74^oE and the focal depth is about 10.Skin. Combining the predominant distribution of the earthquake sequence, the focal mechanism of the main shock and the tectonic conditions of N-E- and NW-strike faults growth in the seismic region, we infer that the main shock of the earthquake sequence was caused by a NW striking buried fault in the Rnichang basin. The nature of seismic faults needs to be further explored.     

Hydrochemical and bacteriological features of the groundwater: southern border of the Rharb basin (Morocco) / Caractérisation hydrochimique et bactériologique des eaux souterraines: bordure méridionale du bassin du Rharb (Maroc)

Abstract

The western reservoirs represent the principal groundwater system in Morocco. Demographic, industrial and agricultural developments during the last decade have markedly altered groundwater quality. The Mamora coastal aquifer system is among the Atlantic systems which are most heavily threatened by pollution. Agricultural and industrial activities, and rapid urban growth contribute to the pollution of the groundwater. Contamination transport is facilitated by a high permeability of the aquifer formations. In order to assess the actual groundwater quality of the Mamora aquifer and to understand the influence of the factors generating the pollution, an extensive multidisciplinary research programme is in progress, with hydrochemistry and microbiology playing essential roles. The present paper concerns the spatial distribution of physico-chemical parameters in the groundwater, subjected to domestic, industrial and agricultural pollution. Fifty-seven samples were analysed for several parameters (Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^?, SO₄ ^2?, HCO₃ ^?, NO₃ ^?, pH, electrical conductivity and temperature). The microbiological analysis of 143 samples reveals the presence of four kinds of indicator bacteria in the groundwater resources: faecal Streptococci, faecal coliform, Escherichia coli and Clostridium. The physico-chemical results and bacteriological monitoring show that the nitrate and bacteria concentrations exceed the maximum admissible levels, notably around pumping stations in the sectors of Sidi Taibi, Sidi Ahmed Taleb and Aïn Sbaâ. Contamination is generated by uncontrolled anthropogenic activities and accentuated by the high intrinsic vulnerability of the aquifer system. Several parameters appeared to exceed admissibility standards. Measures are recommended to prevent groundwater pollution in the region.     

Zink in der Umwelt

Zinc in the Environment. In 1990 the world production of zinc ammounted to 7 Mio. metric tons. The main areas of application were: galvanization, alloys like brass and zinc metal. The content in the earth crust varies between 10–300 ppm zinc with a mean of 70 ppm. Uncontaminated surface waters contain less than 10 mg/m³ zinc. Apart from civilization air contains 1–10 ng zinc per m³. These background concentrations are exceeded by orders of magnitude in zinc deposit areas and where anthropogenic influences predominate. Accumulation can occur in sediments and sewage sludge. Molluscs and Algae also accumulate zinc. Zinc is essential for live. With normal food the zinc supply of man is just sufficient. Bioaccumulation of zinc towards man or chronic oversupply of man is not known. Zinc has no teratogenic or mutagenic effects, a suspicion on a carcinogenic effect proved wrong. In stockbreeding and plant cultivation a minimum supply of zinc is necessary. Plants are relatively less sensitive against higher soil contents of zinc. Considering the toxicological and ecotoxicological effects of zinc in the environment, the critical organismens are marine invertebratae like tubifex, daphnia, gammarus and algae. But normally only a minor part of the total zinc contest is biologically available, depending on salt content and pH of the waters.