渤海湾盆地北部奥陶纪岩相古地理   总被引：8，自引：0，他引：8  

金振奎  邹元荣  由伟丰  蒋春雷 《沉积学报》2002,20(1):13-19

渤海湾盆地北部主要包括黄骅坳陷、沧县隆起、冀中坳陷和下辽河坳陷,区内奥陶系厚 6 0 0～ 80 0m,主要由石灰岩和白云岩组成。下奥陶统分为冶里组和亮甲山组,中奥陶统分为下马家沟组、上马家沟组和峰峰组,上统缺失。其中下马家沟组、上马家沟组和峰峰组又进一步划分为下段和上段。早奥陶世冶里期和亮甲山期,本区以局限海环境为主,其内散布着一些潮坪和滩。中奥陶世,本区岩相古地理面貌变化旋回极为明显,下马家沟期早期潮坪广布,晚期以局限海为主;上马家沟期早期又是潮坪广布,晚期以开阔海为主;峰峰期早期潮坪广布,晚期又以开阔海为主。在奥陶纪,本区经历了 4个大的海侵-海退旋回,其中上马家沟期晚期是本区乃至整个华北地台的最大海侵期。  相似文献   

秦岭若干重要类型金矿床成矿地质条件研究新进展   总被引：6，自引：0，他引：6  

韦龙明  吴列善  黄建军  李福东  朱华平  邹湘华  张万业  任小华 《矿产与地质》2002,16(2):65-69

通过秦岭金矿区域成矿地质条件研究取得的进展 :八卦庙矿区发育有条带状的热水沉积岩 ,金矿床类型属于热水沉积韧性剪切带改造型 ,矿化类型为细脉浸染型 ;马鞍桥金矿的成矿大地构造环境属于华北板块南缘 ,含矿岩系为早古生代的深水斜坡浊积岩相 ,矿区的“浅色岩相”系变质成因 ;煎茶岭金矿属构造蚀变岩型金矿 ,而非超基性岩浆热液型金矿。以上研究为秦岭地区金矿找矿指出了新方向和新类型  相似文献   

Momentum transport of wave zero during March: A possible predictor for the Indian summer monsoon     

S. M. Bawiskar  V. R. Mujumdar  S. S. Singh 《Journal of Earth System Science》2002,111(2):153-157

Analysis of monthly momentum transport of zonal waves at 850 hPa for the period 1979 to 1993, between ‡S and ‡N for January to April, using zonal (u) and meridional (v) components of wind taken from the ECMWF reanalysis field, shows a positive correlation (.1% level of significance) between the Indian summer monsoon rainfall (June through September) and the momentum transport of wave zero TM(0) over latitudinal belt between 25‡S and 5‡N (LB) during March. Northward (Southward) TM(0) observed in March over LB subsequently leads to a good (drought) monsoon season over India which is found to be true even when the year is marked with the El-Nino event. Similarly a strong westerly zone in the Indian Ocean during March, indicates a good monsoon season for the country, even if the year is marked with El-Nino. The study thus suggests two predictors, TM(0) over LB and the strength of westerly zone in the Indian Ocean during March.  相似文献   

STRESS-METAMORPHISM AND ISOTOPIC AGE OF SHEAR ZONE GRANITOID TECTONITES OF IRTYSH SHEAR ZONE (ALTAI REGION)   总被引：1，自引：0，他引：1  

B.M.Chikov  V.A.Ponomachuk  S.V.Zinoviev  B.N.Lapin  A.T.Titov  A.V.Travin  S.V.Palessky 《大地构造与成矿学(英文版)》2002,26(1):36-51

The Irtysh shear zone (ISZ) of Altai region is the lineament structure of the collision-suture type, where granites of Kalba complex and granodiorites of Zmeinogorsk complex are exposed to regional gneiss-formation and stress-metamorphic alterations. This study is based on detailed structural observations at special grounds using optical and electron microscopy, and on the behavior analysis of isotopic systems from altered granitoids.Within the ISZ area we have established the continuous rows of granitoid stress-metamorphism from initial recrystallization of protolite, its cataclasis and mechanical flaring up to complete recrystallization with alteration of mineral composition and formation of the streaky complexes of granite tectonites of blastomylonite and blastocataclasite types. The directed alteration of rocks has several impulse and is expressed by a change in morphology of mineral grains and their relations, magnification of deformation component in the rock structure, and formation of new mineral phases on the basis of initial ones without surface fluidization. At transformation of isotopic systems from granitoid, their feldspars,biotite and hornblende, we can observe “rejuvenation“ of the rock substrate from 270- 290 Ma for Kalba granitoids to 220-235 Ma for their tectonites, and for Rudny Altai granodiorites, their ages changes from 285-317 Ma to 232-257 Ma for their tectonites.  相似文献   

新疆伽师及邻近地区现今地壳形变的GPS监测与研究   总被引：8，自引：2，他引：8       下载免费PDF全文

王晓强  王琪  程瑞忠  乔学军  李杰  张永岗  海力 《地震工程学报》2002,24(3):199-207

利用高精度数据软件对伽师及邻近地区的GPS监测网观测数据进行计算分析(基线精度达到了 10 - 8～ 10 - 9) ,获得了该地区的现今地壳形变速率图 .结果表明 ,伽师及邻近地区在印度板块的推挤作用下 ,地壳正快速缩短变形 ,主压应力为近南北方向 .各地块运动速率不同 ,平均应变率为 0 .0 4× 10 - 6 /a .  相似文献   

四川省房屋建筑易损性研究   总被引：3，自引：0，他引：3  

何玉林  黎大虎  范开红  刘盛利 《中国地震》2002,18(1):52-58

研究房屋建筑易损性特征是防震减灾工作必不可少的环节之一，本文通过对多年工作的系统总结，得出四川省不同地区的房屋建筑易损性矩阵，全省房屋建筑抗震性能总体水平不高，这是造成地震灾害加重的主要原因之一，随着经济发展实力的提高，适当提高全省房屋建筑抗震设防水平可大大减轻特别是中强地震所造成的经济损失。  相似文献   

华北近十年来水平运动动态与地震活动危险区的讨论     

周晓燕  杨国华  韩月萍 《华北地震科学》2002,20(4):28-33

根据华北地区1999年和2001年两期高精度GPS观测结果，通过与1992，1995，1996年和1999年这几期资料的比较，发现近两年的运动与前有所不同，主要表现为：（1）阴山单元和鄂尔多斯单元之间显示为压性运动的性质，但比较微弱，它们之间的边界带上似乎有左旋走滑运动，但从整体上看并不显著。（2）晋冀鲁单元和燕山单元的整体活动性不如以前，各单元内部存在着较明显的差异运动，并山单元和晋冀鲁单元的北部存在着比较显著的东西向挤压，北京地区则表现为南北向挤压。（3）晋冀鲁单元南部与胶辽鲁苏单元的南部的趋势活动呈张性，优势运动方向为东南，这样的结果可能表明，华北目前存在着应力扰动行为，大同与天津之间的区域是受其影响最大的地区，该区有可能成为未来几年中强地震活动的一个主体地区。  相似文献   

African monsoon variability during the previous interglacial maximum     

E.J. Rohling  T.R. CaneS. Cooke  M. SprovieriI. Bouloubassi  K.C. EmeisR. Schiebel  D. KroonF.J. Jorissen  A. LorreA.E.S. Kemp 《Earth and Planetary Science Letters》2002,202(1):61-75

Little is known about centennial- to millennial-scale climate variability during interglacial times, other than the Holocene. We here present high-resolution evidence from anoxic (unbioturbated) sediments in the eastern Mediterranean Sea that demonstrates a sustained ∼800-yr climate disturbance in the monsoonal latitudes during the Eemian interglacial maximum (∼125 ka BP). Results imply that before and after this event, the Intertropical Convergence Zone (ITCZ) penetrated sufficiently beyond the central Saharan watershed (∼21°N) during the summer monsoon to fuel flooding into the Mediterranean along the wider North African margin, through fossil river/wadi systems that to date have been considered only within a Holocene context. Relaxation in the ITCZ penetration during the intra-Eemian event curtailed this flux, but flow from the Nile - with its vast catchment area - was not affected. Previous work suggests a concomitant Eurasian cooling event, with intensified impact of the higher-latitude climate on the Mediterranean basin. The combined signals are very similar to those described for the Holocene cooling event around 8 ka BP. The apparent type of concurrent changes in the monsoon and higher-latitude climate may reflect a fundamental mechanism for variability in the transfer of energy (latent heat) between the tropics and higher latitudes.  相似文献   

城市震害高危害小区的研究和GIS的实现技术   总被引：3，自引：2，他引：3  

帅向华  成小平  袁一凡 《地震》2002,22(3):113-119

论述了在城市地震灾害中如何考虑诸方面因素来评价城市的灾害轻重分布情况。中建立坑危害小区分析模型，设想将城市划分等面积网格，给每个单元网格赋予灾害指数，以确定城市中受灾较为严重的区域，为求灾指挥提供决策信息。同时，将高危害小区的模型研究结果转化为计算机技术可以实现的GIS模型。该研究结果已应用于泰安市防震减灾示范研究项目中。  相似文献   

Shallow seismicity, stress distribution and crustal deformation pattern in the Andaman-West Sunda arc and Andaman Sea, northeastern Indian Ocean     

M. Radha Krishna  T.D. Sanu 《Journal of Seismology》2002,6(1):25-41

Shallow seismicity and available source mechanisms in the Andaman–westSunda arc and Andaman sea region suggest distinct variation in stressdistribution pattern both along and across the arc in the overriding plate.Seismotectonic regionalisation indicates that the region could be dividedinto eight broad seismogenic sources of relatively homogeneousdeformation. Crustal deformation rates have been determined for each oneof these sources based on the summation of moment tensors. The analysisshowed that the entire fore arc region is dominated by compressive stresseswith compression in a mean direction of N23^°, and the rates ofseismic deformation velocities in this belt decrease northward from 5.2± 0.65 mm/yr near Nias island off Sumatra and 1.12 ±0.13 mm/yr near Great Nicobar islands to as much as 0.4 ±0.04 mm/yr north of 8^°N along Andaman–Nicobar islandsregion. The deformation velocities indicate, extension of 0.83 ±0.05 mm/yr along N343^° and compression of 0.19 ±0.01 mm/yr along N73^° in the Andaman back arc spreadingregion, extension of 0.18 ± 0.01 mm/yr along N125^° andcompression of 0.16 ± 0.01 mm/yr along N35^° in NicobarDeep and west Andaman fault zone, compression of 0.84 ±0.12 mm/yr N341^° and extension of 0.77 ± 0.11 mm/yralong N72^° within the transverse tectonic zone in the Andamantrench, N-S compression of 3.19 ± 0.29 mm/yr and an E-Wextension of 1.24 ± 0.11 mm/yr in the Semangko fault zone ofnorth Sumatra. The vertical deformation suggests crustal thinning in theAndaman sea and crustal thickening in the fore arc and Semangko faultzones. The apparent stresses calculated for all major events range between0.1–10 bars and the values increase with increasing seismic moment.However, the apparent stress estimates neither indicate any significantvariation with faulting type nor display any variation across the arc, incontrast to the general observation that the fore arc thrust events showhigher stress levels in the shallow subduction zones. It is inferred that theoblique plate convergence, partial subduction of 90^°E Ridge innorth below the Andaman trench and the active back arc spreading are themain contributing factors for the observed stress field within the overridingplate in this region.  相似文献