基于钻探的芦花台隐伏断层晚第四纪活动特征

芦花台断层是银川盆地内一条重要的隐伏构造。在浅层地震勘探成果的基础上,开展了钻孔联合剖面探测和钻孔样品测试,获得了断层上断点埋深、最新活动时代、晚第四纪累计位移和滑动速率等数据。结果表明:芦花台隐伏断层北段和南段的活动性不同,南段为中更新世末活动断层,北段为全新世活动断层;在北段内,断层活动强度在空间上表现为由北向南增强,在时间上表现为晚更新世活动强于全新世。     

银川市活断层探测进展概述

本文介绍了对银川市城区两条隐伏断层所做的多层次、多手段综合探测,包括在同一个试验场点进行的三个层次的浅层人工地震勘探、钻孔联合剖面探测和槽探,从深到浅,逐层捕获隐伏目标,直到明确锁定目标断层在试验场点的准确位置、产状和上断点埋深等情况。通过对银川市活断层探测中目标断层的追踪探测,查明了市区银川隐伏断层和芦花台隐伏断层的平面展布,特别是在市区的延伸位置。通过岩芯样品的绝对年龄测定,得到了银川隐伏断层北段晚全新世活动,南段晚更新世活动,芦花台断层晚更新世以来不活动的结论。     

利用井间地震层析成像方法探测隐伏断层

针对目前隐伏断层探测中存在的技术难题,提出了在地面反射地震勘探初步确定的断点附近,用井间地震层析成像方法探测隐伏断层及其上断点的埋深。首先介绍井间地震技术的应用现状和井间地震层析成像的基本原理,并结合实例讨论了井间初至走时层析成像的野外数据采集和室内资料处理方法。芦花台隐伏断层的井间地震层析成像结果表明,采用弯曲射线追踪方法反演得到的跨芦花台隐伏断层的井间纵波速度结构图像与钻孔联合剖面揭示的断层特征相吻合。      

浅层人工地震和地质雷达在城市活动断层探测中的联合应用?以鹤壁市汤东断裂为例

浅层人工地震勘探是探查城市隐伏活动断层最有效的手段之一,然而受近地表探测盲区和探测分辨率的限制,该方法难以获取活动断层超浅层上断点的准确埋深位置。地质雷达探测方法在一定程度上可弥补浅层人工地震勘探的不足。为探索浅层人工地震勘探和地质雷达探测的联合应用效果,分析其在城市隐伏活动断层探测中的应用潜力,选取河南省鹤壁市汤东断裂西支为研究对象,并在冯屯村和前交卸村分别开展联合探测,获取高信噪比的浅层人工地震反射剖面和地质雷达剖面。浅层人工地震勘探揭示的冯屯村处汤东断裂西支上断点埋深为60～70 m,地质雷达探测揭示的上断点埋深约为2.5 m,结合平均沉积速率推测汤东断裂西支在冯屯村的最新活动时代约为25 ka。浅层人工地震勘探揭示的前交卸村处汤东断裂西支上断点埋深为50～60 m,地质雷达探测揭示出汤东断裂西支在前交卸村处未造成近地表约10 m以内的地层断错。研究结果表明,在城市隐伏活动断层探测中,采用浅层人工地震勘探和地质雷达探测相结合的方法,不但可有效确定活动断层的位置,且可进一步约束活动断层上断点的准确埋深,有利于指导后期地震地质勘探中的探槽和钻孔布设。     

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     

隐伏活动断层的多层次综合探测——以银川隐伏活动断层为例

以银川活动断层试验探测为例,介绍了第四纪巨厚沉积区隐伏断层多手段、多层次探测的步骤与方法。在对前人资料综合分析的基础上,选择银川市兴庆区新渠梢村为综合探测试验场。首先,分层次布施道间距10m、5m和1m的浅层人工地震勘探,由深至浅将银川隐伏断层主断层逐步控制在可以布施浅钻勘探的程度。然后,实施钻孔联合剖面探测,确定了断层的准确位置和倾角,获得了由钻探资料可分辨的断层上断点埋深8.3m的信息。最后,通过大型探槽开挖,查明了断层实际上断点埋深1.5m和5期古地震活动事件。结合地层年龄的初步测定,得出了银川隐伏断层主断层中—晚全新世活动的结论     

第四纪沉积区断层及其上断点探测的地震方法技术——以银川隐伏活动断层为例

地震勘探方法是隐伏断层探测的一种有效的地球物理探测手段,而地震勘探的探测参数是影响探测效果和断层定位精度的主要因素.本文以银川市活断层探测的浅层地震勘探资料为例,并结合石油地震勘探剖面结果和钻孔地质资料,阐述了在第四纪覆盖层较厚的地区,由深至浅追踪目标断层形态和确定断层上断点空间位置的方法技术.结果表明,采用高分辨率地震勘探和钻孔地质剖面相结合的探测方法是确定隐伏断层位置、判定断层活动性的有效方法.     

3维反射地震方法在活断层探测中的应用试验——以芦花台断层为例

为了试验3维反射地震方法在活断层探测中的应用效果,采用8线10炮的束状观测系统在银川盆地进行浅层3维反射地震试验,得到了反映芦花台断层3维空间结构的数据体。精细处理和综合解释的结果显示,芦花台断层由2条相向倾斜的隐伏正断层组成,主断层倾向SE,次断层倾向NW,二者在平面上的距离由北向南逐渐加大,在深度780~800m次断层归并到主断层上。主断层的上断点埋深自北向南逐渐加深,在试验区的北部上断点埋深为25~30m,而在试验区的南部上断点埋深为35~40m。试验结果表明,3维地震资料具有数据量大、信息丰富、偏移归位准确和断层成像精度高的特点,可以从不同方面反映地层、断层的3维空间展布形态,有利于复杂构造和断层的成像。     

城市活动断层探测中的浅层地震勘探数据库建设——以石嘴山市活动断层探测为例

浅层人工地震勘探是城市活断层探测工程中的重要部分。浅层地震勘探数据库记录测点位置、测线分布图、断点位置等详细信息。本文以宁夏石嘴山市活动断层探测为例,重点介绍了针对石嘴山市内四条隐伏断裂所布设的33条浅层地震勘探测线数据库建设的数据库模型、技术方法、操作技巧及注意事项,为城市活断层探测中基于 ArcGIS等平台系统建立浅层地震勘探数据库提供借鉴。     

西秦岭北缘断裂漳县盆地段浅层人工地震及钻孔联合探测

在地质调查与盆地区浅层人工地震初步勘探基础上,在西秦岭北缘断裂带漳县盆地隐伏段的盆地内布设了3条浅层人工地震详勘测线,用于精确定位该断层的空间展布,判定其浅地表活动特征。在此基础上,用钻孔联合剖面方法对人工地震探测结果进行验证,同时确定了各地震测线处断层上断点的位置和埋深,通过钻孔揭露断层错断地层的特点,认为西秦岭北缘断裂漳县盆地隐伏段错断全新统,指示该断层全新世以来活动性较强。     

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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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.