印尼8.7级地震对辽宁地区的影响

2004年12月26日印度尼西亚苏门答腊岛附近海域发生8．7级强烈地震，震后对辽宁省的数字化前兆观测和辽宁省及其周边地区的小震活动进行了清理研究，结果显示：①震后一个月内在东北地区小震活动明显有一个增强过程，可能与该地震的触发有关。②地下流体和形变观测都记录到清晰的同震震波、同震阶跃和震后震荡现象，出现了显著的前兆同震响应。表明尽管前兆观测不能像地震波那样可较充分地展示关于地震震源的信息，但仍可能反映地震波传播过程中的地壳介质的某些变化特征。     

岷县—漳县6.6级地震洞体应变异常特征

对宕昌地震台洞体应变观测资料异常变化进行分析,认为EW分量记录到岷县—漳县6.6级地震地形变过程,即震间形变→震前形变(包括加速变化期和失稳期)→同震形变→震后形变(包括震后滑动和震后调整)→震间形变。长时间的震后滑动记录在中国较为少见,此观测资料为地震孕育过程的研究提供了宝贵资料。     

天山北部强震活动对区域应力扰动的分析以2012年伊犁M6.6地震和2017年精河M6.6地震为例

天山地区为典型地震活跃区, 为定量分析该构造活跃区强震对周边构造变形和地震活动的影响, 本文基于地震位错理论和岩石圈分层模型计算了天山北部近期发生的2012年伊犁和2017年精河两次M6.6地震对周围地壳形变和应力的影响。 计算结果显示伊犁地震和精河M6.6地震引起震中附近地表同震位移达数厘米, 地表同震应变量级约为10^-7; 对比天山北部地区年平均构造形变特征, M6.6强震释放了震中附近近十年的构造主压应变积累; 地震引起震中附近(80 km内)同震库仑应力变化大于1 kPa, 而距震中较远区域活动断层上库仑应力变化微弱。 结合天山北部现今地壳变形特征及区域地震分布, 初步推测两次M6.6地震的发生对震后余震有显著的触发作用, 而对区域后续微震活动的影响微弱。     

日本9.0级地震震后体应变驰豫效应

2011年3月l1日日本发生MW 9.0强烈地震,泰安地震台地震前兆体应变记录到显著震后异常,即震后弛豫效应,结合GPS数据,探讨地壳应力新平衡状态调整过程及地形变调整机理,为数据跟踪分析提供地球物理事件识别及判定依据。     

地表动态大地测量资料反映的孕震断层变形机制研究

正构造地震孕育、发生、震后调整过程中应力应变积累、释放必然伴随有相应的地壳形变发生。利用大地测量动态资料研究与地震过程密切关联的地壳形变时空动态特征是地震预测研究的重要途径之一。由于构造地震发生在活动断层上(通常在10km以下的深部),因此,如何建立逼近真实的地表形变动态变化与孕震断层深浅部应力应变状态的关系,以揭示孕震     

特大远震引起的形变观测变化图像

利用定点长水管倾斜仪、石英伸缩仪、金属摆倾斜仪、石英摆倾斜仪连续观测资料对特大远震引起的震时和震后形变效应进行了分析.分析结果表明定点连续形变观测台网能记录到不同方位地震的震时脉冲信号,其持续时间半小时到4小时;同时还能记录到一些地震的阶跃信号.水平摆倾斜仪（金属摆、石英摆）观测值的震后效应表现为大幅漂移,持续时间几天到一个月.对由特大远震引起的形变观测变化图像出现差异的原因进行了讨论.另外对震时阶跃变化图像、定点形变观测仪器长趋势的漂移项、观测台站所处的地质构造三者之间的关系进行了讨论.     

MS8.0汶川地震对MS7.0芦山地震成核失稳的影响

依据速率-状态依赖性摩擦本构关系,并结合中下地壳和上地幔的黏弹性松弛效应,以震后库仑破裂应力变化和同震动态库仑破裂应力变化的计算为基础,模拟了两种应力变化对芦山地震断层的失稳发震时间的影响,研究了2008年M_S8.0汶川地震与2013年M_S7.0芦山地震之间的触发关系.计算得到,汶川地震在芦山地震震源断层面上产生的动态应力变化的峰值为0.127 MPa;此外,经过近5年中下地壳和上地幔的黏弹性松弛效应,芦山地震震源断层面上受到的震后应力变化值为0.025 MPa.结果表明,芦山地震的震源断层在应力积累逐渐接近临界状态的某一特定时期内,受到了汶川地震产生的动态应力变化、静态应力变化以及黏弹性松弛效应造成应力变化的共同触发作用,且动态应力的延迟触发作用可能更为显著.最后对芦山地震之后研究区域的应力变化场进行了初步探讨.     

M_s8.0汶川地震对M_s7.0芦山地震成核失稳的影响Mw

依据速率-状态依赖性摩擦本构关系,并结合中下地壳和上地幔的黏弹性松弛效应,以震后库仑破裂应力变化和同震动态库仑破裂应力变化的计算为基础,模拟了两种应力变化对芦山地震断层的失稳发震时间的影响,研究了2008年Ms8.0汶川地震与2013年Ms7.0芦山地震之间的触发关系.计算得到,汶川地震在芦山地震震源断层面上产生的动态应力变化的峰值为0.127 MPa;此外,经过近5年中下地壳和上地幔的黏弹性松弛效应,芦山地震震源断层面上受到的震后应力变化值为0.025 MPa.结果表明,芦山地震的震源断层在应力积累逐渐接近临界状态的某一特定时期内,受到了汶川地震产生的动态应力变化、静态应力变化以及黏弹性松弛效应造成应力变化的共同触发作用,且动态应力的延迟触发作用可能更为显著.最后对芦山地震之后研究区域的应力变化场进行了初步探讨.     

基于三维粘弹性有限元进行汶川地震对川滇地区震后影响研究

正国内外相关研究表明,一次大地震同震及震后形变场(介质粘弹性松弛效应引起)不仅与地壳介质纵向分层有关,也与地壳介质的横向不均匀性有关,特别是中下地壳粘滞系数较小的粘弹性层的存在,对震后形变场与应力场的时空分配具有重要的作用。另外,发震断层两侧同震形变的非对称性对相关区域震后形变场也具有重要的作用。因此,在研究由于地壳介质粘弹性松弛效应引起的震后变形场之前,首先应得到和实际观测同震形变场(特别是远场     

岩石圈结构对大地震震后形变的影响——以1976年唐山大地震和2001年昆仑山大地震为例

大地震发生之后通常会诱发一系列的余震序列，对比1976年M_S7.8唐山大地震和2001年M_S8.1昆仑山大地震周边区域的地震事件可以看出，唐山大地震余震活动时间要明显长于昆仑山大地震余震活动时间.余震序列往往与震后形变密切相关，而影响震后形变的因素不仅与地震发震断层和震级有关，同时与岩石圈的结构有关.考虑到唐山大地震的发震区华北地块和昆仑山大地震的发震区青藏高原有着较大的岩石圈结构差异，本文采用PSGRN/PSCMP软件计算了岩石圈分层模型的大地震同震和震后形变，分析了地壳弹性模量、弹性厚度以及黏滞性系数对同震和震后形变的影响，进而讨论了影响唐山地震和昆仑山地震余震序列差异的原因.计算结果显示，震后形变会在黏弹性效应的作用下逐渐调整，震后形变的持续时间与地壳弹性模量、地壳弹性厚度和下地壳黏滞性系数有关.上地壳和下地壳弹性模量越大，震后形变达到稳定值的时间越短，弹性模量对震后形变稳定值影响很小.地壳弹性厚度越大，震后形变达到稳定值的时间越短，当断层面底端深度小于地壳弹性厚度时，地壳弹性厚度的增加会引起震后形变稳定值的减小；下地壳厚度对震后形变达到稳定值的时间和稳定值基本无影响.下地壳黏滞性系数越大，震后形变达到稳定值的时间越长，反之亦然.结合唐山地震区的华北地块和昆仑山地震的青藏高原深部结构发现，两者之间的上地壳弹性模型差别不大，唐山地震区地壳弹性厚度略大于昆仑山地震区，但昆仑山地震区下地壳黏滞性系数明显低于唐山地震区.这些因素均决定了昆仑山地震的震后形变持续时间短（余震时间序列短）而唐山地震的震后形变持续时间长（余震时间序列长）.由此可见，岩石圈结构差异可能是导致唐山地震和昆仑山地震余震序列差异的主要因素之一.     

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     

Calendar of events

正~~     

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.