渭河断裂西段活动差异性分析   总被引：17，自引：0，他引：17  

冯希杰田勤俭  申旭辉 《地质论评》2003,49(3):233-238

渭河断裂是一条纵贯渭河盆地中部的大断裂，对渭河盆地的形成和发展乃至盆地内的地震活动都具有控制作用。本文将宝鸡峡口以东，西安市草滩镇以西的渭河断裂西段作为研究区。从渭河断裂北侧黄土台源地貌存在的分级现象、自西向东渭河断裂新近系错距大小非均匀变化、渭河断裂西段断坎地貌差异等方面的分析，讨论了渭河断裂西段存在的活动差异性，认为以千河断裂、岐山-马召断裂和泾河推测断裂为分界点，渭河断裂西段可分为三个亚段，各个亚段在断裂活动时间、活动强度等方面均有明显的差异。通过对渭河断裂西段所处新构造环境的分析，认为第四纪以来渭河盆地西部地壳的向东掀斜拾升运动是造成渭河断裂西段出现差异性活动的根本原因。  相似文献   

Magnetic activity inside the auroral zones and field-aligned currents     

Jean-Louis Le Mouël  Pierre-Noël Mayaud  Peter Shebalin 《Comptes Rendus Geoscience》2003,335(13):935-941

Big perturbations of the magnetic field (amplitudes larger than 250 nT) are simply detected by subtracting the values of a model from the measurements of CHAMP satellite. Taking a full year of CHAMP data and organizing them in four subsets of three months length (spring, summer, autumn, winter), it is found that: (a) the two domains where such big perturbations mainly exist are limited, in both hemispheres, by a parallel of high latitude of the corrected geomagnetic coordinates system; (b) a conspicuous seasonal (annual) variation affects the density of the perturbations and is opposite in the two hemispheres. We hold that these perturbations are linked to the midday magnetic activity within the auroral zone, long ago described by one of us (Mayaud, 1956). The source of the perturbations observed at the satellite altitude would be field-aligned currents resulting from the penetration of the solar wind into the magnetospheric cusps. To cite this article: J.-L. Le Mouël et al., C. R. Geoscience 335 (2003).  相似文献   

Predictive GIS-Based Model of Rockfall Activity in Mountain Cliffs   总被引：6，自引：1，他引：6  

Marquínez  J.  Menéndez Duarte  R.  Farias  P.  JiméNez Sánchez  M. 《Natural Hazards》2003,30(3):341-360

Rockfall susceptibility has been analysed in mountain cliffs of the Cantabrian Range, North Spain. The main aim of this analysis has been to build a predictive model of rockfall activity from a low number of environmental and geological variables. The rockfall activity has been quantified in a GIS. The cartographic information used shows the spatial distribution of all the recent talus screes as well as their associated source areas in the rock-slopes. The area relation At/Ar (recent talus scree polygon/source basins) in the rock slopes has been used as the rockfall activity indicator. This relation has been validated in 50 pilot rock-slopes and compared with the relation number of recent rock fragments/source basin, obtained from field work. The environmental factors causing rockfall depend on the rock slope situation, and these are: altitude and sun radiation on the rock cliff. The geological factors considered are: lithology, relative position of the main discontinuities with respect to the topographic surface and two morphologic parameters: the roughness and slope gradient. A logistic regression analysis has been applied to a population of 442 limestone and quartzite rock cliffs. The dependent variable is the rockfall activity indicator, which allows the definition of two classes of rock cliff units: low and high activity. The independent variables are altitude, sun radiation (equinox radiation, summer solstice radiation, winter solstice radiation), slope roughness, slope gradient,anisotropy and lithology. Results suggest that it is possible tobuild a valid cartographic predictive model for rockfall activity in mountain rock cliffs from a limited number of easily obtainable variables. The method is especially applicable in massive rock slopes or in regions with uniform rock mass characteristics.  相似文献   

全球增暖的另一可能原因初探   总被引：14，自引：1，他引：14       下载免费PDF全文

李崇银  翁衡毅  高晓清  钟敏 《大气科学》2003,27(5):789-797

太阳是地球流体(大气和海洋等)运动的最终能量源,地球环境,尤其是气候的变化不能不与太阳活动有关.目前,普遍将全球增暖归结为温室气体含量增加所导致的温室效应的加剧,这无疑是有一定依据和有道理的.但从科学上来讲,人类活动所引起温室气体增加的影响,并非是唯一原因.基于已有的一些研究结果,从太阳活动的观点所进行的初步分析表明,太阳活动也可能是引起近世纪全球增暖的另一个重要原因.太阳活动的影响主要包括太阳辐射的直接影响和引发地磁场变化的间接影响两个方面,地球磁场的变化将可通过动力过程和热力过程而影响大气环流和气候的变化.  相似文献   

浅述五大连池火山区浅层气体钍、氡与断裂构造和火山活动的关系     

孙如波  高清武  潘玉林  杨森林 《东北地震研究》2003,19(4):9-17

在五大连池火山区流体化学研究原有工作的基础上，对火山群的重要区段开展了野外踏勘、气体普查，特别是用放射性气体测量方法对火烧山、老黑山、笔架山、药泉山等火山区进行了Tn、Rn测量。通过大量实测资料，分析和研究了Tn、Rn等气体和火山、火山活动、断裂构造、断裂活动性及其他地质条件的关系，初步查明了五大连池火山区的气体组成特征、分布和形成规律，对地下主要气体的成因、气体和火山构造活动及其它地质条件的关系进行了初步探讨，并提出了对五大连池火山区气体观测的初步设想和建议。  相似文献   

昆仑山口西8.1级地震前青藏块体边界断层异常活动   总被引：5，自引：0，他引：5  

范燕  车兆宏 《地震》2003,23(2):121-126

系统分析了青藏块体边界断层的形变资料，研究了断层活动的动态过程及空间分布。结果表明，昆仑山口西8．1级地震前孕震影响范围达到青藏块体的周边地区；发震断层所在的构造带震前断层活动最为剧烈；加强对构造块体断层整体活动的宏观动态比较和分析，有助于判定未来强震发生的危险地段；震后应力将转移并集中到西秦岭构造带及其邻近地区。  相似文献   

青藏及邻区新生代火山活动及构造演化   总被引：12，自引：0，他引：12       下载免费PDF全文

邓万明 《地震地质》2003,25(Z1):51-61

青藏高原是现今地球动力学和地质演化研究的一个热点。该区火山活动受中 -新生代以来高原深部地球物理 -化学反应的控制 ,是多种因素相互作用所表现的形式和结果。本区既有富钾质的 (主导 ) ,也有富钠质的火山岩 (次要 ) ;既有喷发熔岩流 (主导 ) ,也有一些浅源上侵的次火山岩体 ;火山活动发育在古近纪、新近纪与第四纪 ,而最强烈的发生在中新世期间。本区钠质和钾质两类火山岩在形成环境和时代上有很大的差异 :前者一般发育在古新世—始新世 (6 0～ 4 0MaBP) ,而后者主要形成在渐新世—中新世 (30～ 10MaBP) ;存在着钠质—钾质—酸性次火山岩的演化过程 ;大体上可划分为西羌塘、北羌塘、可可西里、中昆仑、西昆仑等 5个火山岩省。本文对比了青藏高原及邻区甘肃礼县和云南三岩区 (金沙江北段、腾冲和滇东南地区 )新生代火山岩的岩石组合、同位素年代学以及地球化学特征 ,大量的证据表明 ,这些火山岩形成在原始地幔、或“壳 -幔过渡带”或陆壳基底等源区。在实际考察和综合研究的基础上 ,探讨了岩石圈的区域构造特征及其与高原隆升的关系等  相似文献   

泰国三塔断裂活动性及其板缘动力学意义     

张建国  乔森  周瑞琦  胡耀雄  Wanchai Silpon 《地震研究》2003,26(1):6-13

通过对位于印度板块与欧亚板块碰撞带缅甸弧附近三塔断裂带活动性的野外考察研究，探讨了位于缅甸弧东侧的滇缅泰板缘地区现代构造与地震活动动力来源和空间不均匀性。指出印度板块与欧亚板块沿兴都库什弧的正面碰撞和青藏高原隆起导致的侧向挤出作用对滇缅泰板缘地区现代构造与地震活动的影响可能大于印度板块与欧亚板块沿缅甸弧的碰撞对上述地区的影响。  相似文献   

长江巨洪的强信号探讨     

冯利华 《地球物理学进展》2003,18(4):772-775

分析了1900年以来长江3次巨洪的3个强信号：(1)太阳黑子活动，(2)厄尔尼诺事件，(3)青藏高原南部大震，它们对大气环流异常的影响分别称为日气作用、海气作用、地气作用，依据长江巨洪和3个强信号的基本事实，讨论了长江发生巨洪的统计规律，指出当3个强信号的出现时间互相重叠时，长江很可能发生巨洪，如果再叠加其它信号，长江发生巨洪的量级更大，这对长江巨洪的超长期预期具有重要的指示作用。  相似文献   

Variability of NO₂ in different environments at a moderately polluted island over the southwestern Indian Ocean     

Chatrapatty Bhugwant  Jean-Luc Hoareau 《Atmospheric Research》2003,66(4):241-259

This work presents the temporal evolution and spatial distribution of nitrogen dioxide (NO₂) measured with the help of passive diffusion tubes in different environments: rural, sub-urban, urban, at La Réunion Island in December 1997 and November 2000 (austral spring), respectively. NO₂ concentration exhibits notable enhancement from 1997 to 2000. For instance, its mean concentration was 16 and 20 μg/m³ in December 1997 and November 2000, respectively, at La Réunion Island, especially in inhabited regions due to increase of local anthropogenic activities, mainly traffic circulation, in the absence of house heating and biomass burning. We also observe a net increase of pollutant levels by a factor two in rural/remote areas within 3 years, which is tied to the extension of inhabited areas and air-flows from enhanced local sources. The increase of atmospheric pollutants is mainly due to enhancement of anthropogenic activities (traffic) since the 1990s at La Réunion Island, which results from a constant increase of population and consequently, from a higher number of vehicles in circulation. Importantly, in cities like Saint-Denis, where traffic network has been subject to notable improvement (e.g. single to double lanes, etc.), pollutant levels exhibit little variability as in temperate continental latitudes. Semi-continuous NO₂ concentration measured in parallel with ozone in November 2000 also showed that daytime photochemical ozone production is influenced by pollutant and precursor (NO₂) levels at Saint-Denis, while nighttime ozone increase is mainly tied to dynamical processes. The November 2000 ozone diurnal pattern is notably different from that observed in September 1995, during which a daytime ozone loss was observed, pointing out that atmospheric conditions have been subject to notable changes, i.e., clean to moderately polluted, within a few years at La Réunion Island. The results presented here point out that the ‘source enhancement effect’ is superimposed on dynamical and photochemical processes to influence pollutants variability and hence atmospheric chemistry, in a quite ‘pristine’ tropical oceanic region.  相似文献