青海德令哈巴音郭勒河断裂带的新活动特征   总被引：3，自引：0，他引：3       下载免费PDF全文

刘小龙  袁道阳 《地震工程学报》2004,26(4):303-308

在青海德令哈巴音郭勒河北侧山前冲洪积扇上新发现了一条长约60km的逆断裂带,属于本区NNW-NWW向的柴达木盆地北缘活动断裂系内的一条次级挤压构造。断裂在地貌上表现为明显的挤压逆冲断层陡坎,晚更新世晚期以来的平均垂直滑动速率为0.41±0.27mm/a。探槽剖面确定了三次古地震事件,其年代分别为距今约32.7±1.45ka、15.54±1.32ka和3.2±0.33ka。  相似文献   

SMBR中污染物处理效率随污泥浓度变化的数学模型     

陈兆波  任南琪  呼冬雪  王爱杰 《地球科学进展》2004,(Z1)

以一体式膜生物反应器(SMBR)对生活污水进行处理,研究不同水力停留时间(HRT)条件下污泥浓度对有机物去除率的影响,并对所得试验数据进行曲线拟合,建立有机物去除率与污泥浓度的数学模型。试验结果表明:在溶解氧(DO)浓度为2.0～3.0mg/L的条件下,HRT为3h、2h和1h时,有机物去除率(η)随着污泥浓度的增大而增大,但当污泥浓度增大到6000mg/L时,η增大趋势逐渐减小,并趋于稳定。有机物去除率与污泥浓度的数学模型表明:有机物去除率(η)与水力停留时间(τ)、进水COD浓度(S_o)和污泥负荷率(N_s)等主要运行参数有关,并可以通过调节运行参数τ、S_o和N_s来达到所需要的COD去除率。  相似文献   

江西赣州西北部蛤湖地区拆离伸展构造体系     

汪雄武袁正新  王晓地张建超 《地质通报》2004,23(4):367-373

在江西赣州西北部蛤湖地区发现1条韧性拆离断层，宽1～3km，倾向南东。该断层以震旦系砂页岩的构造片岩化和中酸性火山岩的糜棱岩化为特征。其上盘由5～6条铲式正断层组成，正断层的倾向与拆离断层一致，其中最上部的1条正断层控制了箕状断陷盆地的形成和分布；下盘为笔架山穹隆状复式花岗岩杂岩体及其外接触带的震旦系浅变质地层。这些构造构成了一个在成因上与拆离断层形成有关的伸展构造体系。该体系的形成与区域北东向地垒式隆起局部地段的强烈隆升有关，发生于侏罗纪至晚白垩世，其活动对内生成矿起着重要的控制作用。  相似文献   

Rock magnetism and paleomagnetic stratigraphy of forearc sediments of the Japan Trench, ODP Sites 1150 and 1151     

Toshiya Kanamatsu  Nobuaki Niitsuma 《Island Arc》2004,13(1):180-190

Abstract Magnetic measurements were carried out to investigate rock magnetic properties and paleomagnetic directions of late and middle Miocene sediments recovered from the land side of the Japan Trench during the Ocean Drilling Program Leg 186. Because the low coercive component in natural remanent magnetization (NRM) normalized by anhysteretic remanent magnetization shows that the drilling‐induced magnetization is severe in the sections obtained by the advanced hydraulic piston coring method, careful analyses of demagnetization of NRM using the ‘demagnetization plane’ were carried out to decompose the direction and intensity. Magnetostratigraphic correlation down to the upper Miocene, supplemented by biostratigraphic data, revealed that the sedimentation rates are characterized by drastic changes, with the early Pliocene having the highest rate. This high sedimentation rate is related to the subsidence of the southern deep‐sea terrace of the Japan Trench.  相似文献   

The pelagic community of a gravel pit lake: Significance of Coleps hirtus viridis (Prostomatida) and its role as a scavenger     

Brigitte Auer  Elvira Czioska  Hartmut Arndt   《Limnologica》2004,34(3):187-198

Coleps hirtus viridis was the dominant species of the planktonic ciliate community of Lake Fühlinger See (Germany) during the study in 1999 and 2000. Total ciliate densities ranged from 120 to 42,000 ind. l⁻¹ in 1999 and up to 8,000 ind. l⁻¹ in 2000. Coleps contributed up to 98% to both total ciliate abundance and biomass and made up an average of 64% of the total ciliate biomass. Oligotrichs (Rimostrombidium, Strobilidium) dominated the epilimnetic zone, whereas peritrich ciliates (Pelagovorticella, Vorticella) were predominantly located in the hypolimnion. The population maximum of Coleps changed locations from the epilimnion in early summer to the hypolimnion (up to 40,000 ind. l⁻¹) during stratification. High growth rates in the hypolimnion, presence of endosymbiontic algae and the ability to ingest detritus seem to be important for the success.Growth rates of Coleps in June were determined by Landry-Hassett dilution experiments in both the epilimnion and the hypolimnion. The instantaneous growth rates were similar in both layers (0.6 d⁻¹), but a distinctly higher instantaneous mortality was estimated for the epilimnion. These high loss rates may be due to grazing pressure by cladocerans.The significance of the histophagous feeding of Coleps was evaluated through an experiment using killed zooplankton. Parts of Daphnia magna were incorporated at rates of about 1,100 μm³ ind.⁻¹ h⁻¹ by Coleps without endosymbiotic algae and at rates of 500 μm³ ind.⁻¹ h⁻¹ by Coleps with endosymbionts. These high feeding rates support the conclusion that Coleps can use dead organic matter as an additional food source.  相似文献   

Seismic reflection imaging of an oceanic detachment fault: Atlantis megamullion (Mid-Atlantic Ridge, 30°10′N)     

J.P. Canales  B.E. Tucholke  J.A. Collins 《Earth and Planetary Science Letters》2004,222(2):543-560

We present multichannel seismic reflection data collected over the Atlantis megamullion, at the eastern ridge-transform intersection of Atlantis fracture zone on the northern Mid-Atlantic Ridge, and over its conjugate crust. These data image for the first time the internal structure of a young, well-developed megamullion dome formed by tectonic extension across a long-lived oceanic detachment fault. The exposed, corrugated detachment-fault surface exhibits a sharp, coherent reflection that contrasts with less organized reflectivity of surrounding basaltic seafloor. At the termination of the megamullion the fault is imaged ∼13 km along-strike beneath a volcanic hanging-wall block at a sub-seafloor depth of 0.2-0.5 s two-way travel time, reaching north as far as 30°19′N. The eastward dipping of the fault beneath the hanging-wall block is estimated to be ∼6-14°. The corrugated fault surface is underlain by a continuous, strong, and relatively smooth reflection (D) at 0.2-0.25 s sub-bottom below the central axis of the dome. This reflection deepens up to 0.6 s sub-bottom beneath the western slope and it appears to intersect the seafloor on the eastern slope. We suggest that Atlantis massif formed by sequential slip on two different detachment faults that merged at depth, with breakaways as little as ∼2 km apart. The initial detachment is represented by reflection D, and the second corresponds to the presently exposed fault surface. In this interpretation, much of the sliver between the faults is interpreted to be strongly serpentinized peridotite with reduced seismic velocity; it lies in contact with less altered, higher-velocity mantle below the first detachment, resulting in the strong, smooth character of reflection D. Mantle rocks exposed in the megamullion indicate that the feature formed during a period of extreme tectonic extension and probably limited magmatism. In conjugate crust corresponding to termination of the megamullion, observed sub-bottom reflections are interpreted as base of seismic layer 2A. This layer is as thick as or thicker (∼570-900 m) than layer 2A in normal Atlantic crust, and it suggests that relatively normal crustal accretion occurred by the time the megamullion stopped forming.  相似文献   

Blown‐sand transport rate     

Jinren Ni  Zhenshan Li  Cesar Mendoza 《地球表面变化过程与地形》2004,29(1):1-14

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Average recurrence intervals of strong earthquakes and potential risky segments along the Taiyuan-Linfen portion of the Shanxi graben system   总被引：1，自引：0，他引：1  

易桂喜  闻学泽  徐锡伟 《地震学报(英文版)》2004,17(4):426-437

Introduction In AD 1303, the great Hongtong, Shanxi, earthquake of magnitude 8 caused a very serious disaster, which killed over one hundred thousands people at least (Department of Earthquake Dis- *aster Prevention, State Seismological Bureau, 1995). On the occasion of commemorating this ca-tastrophe having occurred for 700 years, we have important problems that need to be answered: How long the average recurrence interval of the grea…  相似文献   

中国新疆博斯腾湖全新世沉积环境年代学特征   总被引：18，自引：1，他引：18  

张成君  曹洁  类延斌  尚华明 《沉积学报》2004,22(3):494-499

通过对博斯腾湖沉积物湖芯样品进行137Cs,14C-AMS测年分析,湖芯剖面上有明显的1986年的切尔诺贝利核事故蓄积峰,以及1975年和1963年次蓄积峰,这些137Cs蓄积峰对博斯腾湖现代沉积有明显的时标意义。通过质量深度与年代分析,博斯腾湖的沉积速率相对稳定,平均沉积速率为0.13±0.01g/cm2.a。与14C年代获得的中全新世以来的平均沉积速率0.13±0.03cm/a和0.12±0.05cm/a相似,表明博斯腾湖中全新世以来的沉积环境较稳定,并且也说明14C-AMS测年分析所得的结果较为可靠,可以利用博斯腾湖沉积物样品测定的14C年代进行线性回归作年代校正,由于湖泊沉积物中老碳效应的影响,博斯腾湖沉积物有机质14C测年偏老约650a左右。  相似文献   

Seismic tests on reinforced concrete and steel frames retrofitted with dissipative braces     

F. J. Molina  S. Sorace  G. Terenzi  G. Magonette  B. Viaccoz 《地震工程与结构动力学》2004,33(15):1373-1394

Seismic tests have been conducted on two 3‐storey structures protected with pressurized fluid‐viscous spring damper devices. One of the structures was a reinforced concrete frame with clay elements in the slabs, while the other one was a steel frame with steel/concrete composite slabs. The spring dampers were installed through K bracing in between the floors. The tests were performed by means of the pseudodynamic method, which allowed the use of large and full‐size specimens, and by implementing a specific compensation strategy for the strain‐rate effect at the devices. The test results allowed the verification of the adequacy of the attachment system as well as the comparison of the behaviour of the unprotected buildings with several protected configurations, showing the benefits of the application of the devices and the characteristics of their performance. The response of the protected structures was always safer than that of the unprotected ones mainly due to a significant increase of equivalent damping. The increase in the damping ratio depends on the level of deformation. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献