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为实现防灾、减灾的社会,在进一步促进平日防灾对策的同时,从推进具体的战略、根据灾害特性采取各种对策的观点,中央防灾会议2007年6月21日决定,2008年度实施以以下8个项目为重点的防灾对策。1树立减轻大规模灾害的战略思路(1)首都直下型地震以及大规模地震的不断准备。(2)推动大规模水灾对策。为了把任何时间任何地方发生的大地震所造成的灾害控制在最低限度,在正确抓住地震防灾战略进展情况的同时,要加强实现以减灾为目标的各种对策。其中,为确保国家中枢机能的连续性,特别是需要对首都直下型地震采取对策,要推进中央省厅、企业等制定业务… 相似文献
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武汉月湖水生植被重建过程中浮游植物的动态变化 总被引：3，自引：0，他引：3
2004年12月-2005年5月武汉市月湖水生植被重建过程中,对浮游植物进行逐月调查.结果表明,在营养盐浓度较高的条件下,浮游植物仍保持较低的生物量和密度,浮游植物的生长与温度保持一定的相关性,但与湖水营养盐浓度并不存在相关关系.菹草和伊乐藻能使水体的透明度保持较高的状态.浮游植物主要由隐藻和硅藻组成,能形成水华的一些常见种类并未随温度升高而出现,可能与这两种沉水植物的存在改变了浮游植物的群落结构有关.因此,在水温较低的冬季和春季进行水生植被重建是富营养化湖泊治理的有效途径. 相似文献
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铜绿微囊藻在竞争生长条件下对氧化还原电位降低的响应 总被引：10，自引：1，他引：9
在室内研究了有、无伊乐藻存在条件下,不同水平的氮及氮磷比(N/P)对实验体系中附着藻类和浮游藻类生长的影响,结果表明:1)在有沉水植物的体系中,当氮浓度较高时(5 mg/L),浮游藻类对N/P的变化比附着藻类更为敏感;而当氮浓度较低时(2 mg/L),浮游藻类与附着藻类对N/P的响应则没有显著的差异;2)在有沉水植物的体系中,当N/P为15时,随水体中氮浓度的升高,附着藻类的生物量显著增加,但浮游藻类的变化不显著.当N/P为25时,随水体中氮浓度的升高,浮游藻类及附着藻类的生物量均显著升高;3)附着藻类的生物量在无沉水植物(伊乐藻)存在的情况下要比有沉水植物(伊乐藻)存在时高得多,且随氮浓度升高,其生物量的增加量也远高于后者.而对浮游藻类而言,情况则完全相反. 相似文献
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大凉山地区新生代地壳缩短及其构造意义 总被引：6，自引：2，他引：4
大凉山地区位于青藏高原的东南边缘,具体指鲜水河-小江断裂带中段安宁河断裂带和则木河断裂带以东的菱形地区.新生代以来大凉山地区的新构造运动不仅表现为沿区内大凉山断裂带的左旋走滑和逆冲2种分量的断层运动,还表现为轴向近SN的褶皱缩短.利用平衡剖面方法结合误差分析得出研究区的地壳平均缩短量为 (10.9±1.6)km,缩短率为 (17.8±2.2)%.研究区发生缩短变形的时间段主要集中在中新世和上新世(12～3.4Ma BP),结合地壳缩短量计算出的研究区地壳缩短速率为 (1.3±0.2)mm/a.对比沿大凉山断裂带的左旋滑动量,可以看出这种褶皱形式的地壳缩短在沿鲜水河-小江断裂带向SE方向传递左旋位移的过程中起着重要的作用. 相似文献
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《水文科学杂志》2013,58(1):192-205
Abstract Considering the geological conditions of the southwest of Boroujerd and northwest of Doroud, Iran, karst development is analysed with respect to the hydrodynamic behaviour of the main draining springs of the units and the karstic aquifers are classified as either those developed in Cretaceous limestone or those developed in Oligomiocene limestone. For this purpose, the yields of the main karstic springs of the region—Absardeh and Zoorabad (Cretaceous karstic limestone aquifer), Kalamsooz and Azizabad (Oligomiocene karstic limestone aquifer)—were measured and analysed. Analysis of the recession curve is used for hydrodynamical analysis and to construct the conceptual model for estimation of karst development in the selected aquifers. Based on the results, the dynamic storage capacity of the saturated zone in Cretaceous limestone is evaluated as low to medium and that in Oligomiocene limestone as medium to high. The dynamic storage capacity of the unsaturated zone in Cretaceous limestone is evaluated as high and that in Oligomiocene limestone as low to medium. Moreover, the contribution of quickflow in karstic aquifers developed in the Cretaceous limestone drained by the Absardeh and Zoorabad springs is 23.5 and 82.2%, respectively, and that for the Kalamsooz and Azizabad springs (Oligomiocene limestone) is 5.7 and 22.5%, respectively. Flow in the Cretaceous limestone aquifer drained by the Zoorabad Spring is of concentrated type and the main flow occurs in the well-developed karstic conduits. The main flow in the Oligomiocene limestone aquifer, drained by the Kalamsooz Spring, occurs in a network of joints and fractures and the contribution of concentrated flow is very low. The transmissivity of the saturated zone in the karstic aquifer drained by the Zoorabad and Absardeh springs is medium to high and that for the Kalamsooz and Azizabad springs is found to be low. 相似文献
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PCCP（预应力钢筒混凝土管）因其优良性能被广泛应用于我国水利水电及市政给排水等生命线工程的建设中。现有研究多为静力分析,少有学者对PCCP管内流体的动力相互作用开展研究。本文利用ABAQUS对PCCP结构及其管内流体在地震荷载下的双向流固耦合作用进行分析,开展了考虑流固耦合与未耦合条件下管道各个结构层的动力响应。进一步计算了考虑内水压力、地震荷载大小和管内水流速度等条件变化对管道受力变形特性的影响。结果表明:流固耦合模型能更加真实地还原和模拟在役PCCP的工作状态;内水压力显著影响管道的受力状态,PCCP结构随着输水压力的增大逐步由受压状态向受拉过渡,且受拉区域和拉应力峰值逐渐增大;管内水流速对应力场影响很微弱。 相似文献
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Distribution of Natural and Synthetic Estrogenic Steroid Hormones in Water Samples from Southern and Middle Germany Natural and synthetic hormones can reach surface waters via domestic sewage effluents. For drinking water production, bank filtration of river waters is a common procedure and hormone contaminations can potentially reach groundwater levels and drinking water sources. In order to analyse steroid hormones in the different aquatic compartments (raw sewage and effluent, surface water, groundwater, raw and drinking water) of South and Middle Germany, a sensitive analytical method was developed and employed to detect the natural steroid hormones estradiol (E2) and estrone and the synthetic estrogen ethinylestradiol (EE2). Samples which were taken in two subsequent series were subjected to clean‐up and enrichment procedure and subsequently analysed by HPLC‐MS. The limit of quantitation for the method was determined to be 0.05 to 0.5 ng/L, depending on the matrix. By treating the samples with glucuronidases/arylsulfatases, conjugates were amenable to analysis and the sum of conjugates and unconjugated steroids was calculated. In raw sewage, the median of the concentrations of the unconjugated steroids was 7 ng/L for EE2, 1.5 ng/L for E2, and 5.5 ng/L for estrone. After cleavage of conjugates, the medians of total steroids were 9.5 ng/L (EE2), 3 ng/L (E2), and 13 ng/l (estrone). Conjugates therefore contributed up to 50 % of the total steroid concentration in raw sewage. In treated effluents, the concentrations of steroids were much lower than in the raw sewage. The medians of free steroids were determined to be 0.3 ng/L for EE2, 0.2 ng/L for E2, and 2.5 ng/L for estrone. Overall the medians in the effluent were thus less than 10% of those in the influent. Conjugates still contributed significantly (40% and more) to the steroid concentrations (medians: EE2: 0.5 ng/L, E2: 0.8 ng/L, and estrone: 8 ng/L). 相似文献
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The paper gives relationships for predicting reservoir circulation generated by radial and tangential jets. These relationships show the importance of the reservoir's aspect-ratio, and the Reynolds number of the jet.Details are also given of concentration-experiments using the conductivity and fluorimetric methods, and incorporating various inlet and outlet arrangements. Peripheral and radial dispersion-coefficients were obtained, and found to be of the same order of magnitude. These coefficients were dependent on the size of the model and on the local Reynolds numbers. The values of dispersion coefficients for reservoirs are similar to those for one-dimensional open channel flow. 相似文献
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对流层延迟是卫星导航定位的主要误差源,气象观测的数值预报资料可用来计算对流层延迟改正量.本文通过分布于亚洲地区的49个GPS台站一年的实测ZTD资料,对利用欧洲中尺度天气预报中心(ECMWF)分析资料、美国国家环境预报中心(NCEP)再分析资料和NCEP预报资料,计算对流层天顶延迟(ZTD)改正的有效性和可能达到的精度进行了评估,分析了ECMWF和NCEP在亚洲地区的适用程度和其分辨率对计算ZTD精度的影响.研究结果表明:(1)相对于 GPS实测ZTD,用ECMWF资料计算ZTD的bias和rms分别为-1.0 cm 和2.7 cm,优于NCEP再分析资料,可用于高精度ZTD研究和应用;NCEP预报数据计算ZTD的bias和rms分别为2.4 cm 和 6.8 cm,足以满足广大GNSS实时导航定位用户对流层延迟改正的需要.(2)bias和rms呈现明显的季节性变化,总体上夏季大,冬季小;在空间分布上随着纬度的变化不明显,但随高度的增加rms总体上有递减趋势.另外还发现,亚洲东部地区夏季日平均bias和rms和南部热带地区冬季的日平均bias和rms变化相对较大.(3)ECMWF2.5°和0.5°的资料进行了对比分析,发现0.5°分辨率资料的rms比2.5°减小1~5 mm.这些结果,为在亚洲地区的空间大地测量、导航定位和INSAR等工作中,应用ECMWF/NCEP的资料进行对流层大气延迟改正的有效性和可能达到的精度提供了重要参考. 相似文献
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在对郯庐断裂带南段３条韧性剪切带中糜棱岩及围岩进行矿物组合、结构构造观察研究的基础上,对长石矿物进行了多项分析测试,发现长石成分及其结构状态参数的变化与构造应力场的构造作用存在明显的对应关系：随剪切变形作用的加强,长石矿物的结构状态参数呈增大趋势,矿物单位晶胞的体积和斜长石中Ｓｉ／Ａｌ比值随之减小;长石的变形指数（Ｉｓｓ）和斜长石中的钙长石分子（Ａｎ）与岩石的变形强度呈明显的正相关关系。这些研究结果为探讨构造变形场中矿物岩石的变形 变质作用提供了一种简捷有效的手段 相似文献
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DISCUSSION ON THE SEISMOGENIC STRUCTURE OF ZHAN-JIANG BAY AREA FROM THE VIEW OF DEEP FAULT SYSTEM INTERPRETED BASED ON THE GRAVITY DATA 
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下载免费PDF全文 The neotectonics in Zhanjiang Bay area is almost the inferred faults and there are not any active faults seen on the ground surface. So it is difficult for research on the seismogenic structure. This paper analyzes and interpretes the gravity data that can reflect the feature of deep faults and then discusses the seismogenic structure of Zhanjiang Bay area in combination with its geology and earthquake activity. There is a huge NEE-trending high gravity gradient belt lying in the coastal region among Guangdong, Guangxi, and Hainan, and Zhanjiang Bay is located in this gravity gradient belt. We analyzed and interpreted more than eighty images obtained with many different methods one by one, then, got the result that Zhanjiang Bay area is embraced by two giant fault belts trending in the NEE and NW direction respectively, and its interior is crossed over by the NE-trending fault belt. These three fault belts are well shown in the gravity images, especially the NEE-trending fault belt and NW one. The gravity isolines and gradient belts or the thick black stripes of the NEE-and NW-trending fault belts are displayed apparently. Also, these gravity structures are good in continuity, extend vastly and cut deeply. What is more, the NEE-trending fault belt plays a leading and region-controlling part. It shows good continuity, and cuts off the NW-and NE-trending faults frequently and intensively. The NW-trending fault belt also is good in continuity and cuts the NEE-and NE-trending faults relatively frequently and strongly, but it is restricted by the NEE-trending one. Last, the continuity of the NE-trending fault is worse and the strength cutting off NE-and NW-trending faults is significantly weak, just in some segments and in the shallow positions. According to the characteristics above and combined with the analyses of geological structure and earthquake activity, the conclusion can be drawn that the NEE-trending fault is the controlling structure and the main seismogenic structure in Zhanjiang Bay area, and the NW-trending fault is the second one. They conjugate and act together. Therefore, Zhanjiang Bay has the tectonic condition for generating MS=6.5 earthquakes. 相似文献
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Gaku Kimura Yasuyuki Nakamura Kazuya Shiraishi Gou Fujie Shuichi Kodaira Asuka Yamaguchi Rina Fukuchi Yoshitaka Hashimoto 《Island Arc》2021,30(1):e12402
The Nankai Trough, Japan, is a subduction zone characterized by the recurrence of disastrous earthquakes and tsunamis. Slow earthquakes and associated tremor also occur intermittently and locally in the Nankai Trough and the causal relationship between slow earthquakes and large earthquakes is important to understanding subduction zone dynamics. The Nankai Trough off Muroto, Shikoku Island, near the southeast margin of the rupture segment of the 1946 Nankai earthquake, is one of three regions where slow earthquakes and tremor cluster in the Nankai Trough. On the Philippine Sea plate, the rifting of the central domain of the Shikoku Basin was aborted at ~15 Ma and underthrust the Nankai forearc off Muroto. Here, the Tosa-Bae seamount and other high-relief features, which are northern extension of the Kinan Seamount chain, have collided with and indented the forearc wedge. In this study, we analyzed seismic reflection profiles around the deformation front of accretionary wedge and stratigraphically correlated them to drilling sites off Muroto. Our results show that the previously aborted horst-and-graben structures, which were formed around the spreading center of the Shikoku Basin at ~15 Ma, were rejuvenated locally at ~6 Ma and more regionally at ~3.3 Ma and have remained active since. The reactivated normal faulting has enhanced seafloor roughness and appears to affect the locations of slow earthquakes and tremors. Rejuvenated normal faulting is not limited to areas near the Nankai Trough, and extends more than 200 km into the Shikoku Basin to the south. This extension might be due to extensional forces applied to the Philippine Sea plate, which appear to be driven by slab-pull in the Ryukyu and Philippine trenches along the western margin of the Philippine Sea plate. 相似文献
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WEN Xiang ZHOU Bin SHI Shui-ping QIN Jian LI Jia-ning HE Yan YAN Chun-heng LUO Yuan-peng 《地震地质》2019,41(4):927-943
Northwest Guangxi is located in the Youjiang fold belt and the Hunan-Guangxi fold belt of secondary structure unit of South China fold system. The South China fold was miogeosyncline in the early Paleozoic, the Caledonian fold returned and transformed into the standard platform, and the Indosinian movement ended the Marine sedimentary history, which laid the basic structural framework of this area. Since the neotectonic period, large areas have been uplifted intermittently in the region and Quaternary denudation and planation planes and some faulted basins have been developed. Affected by the strong uplift of Yunnan-Guizhou plateau, the topography of the region subsides from northwest to southeast, with strong terrain cutting and deep valley incision. Paleozoic carbonate rocks and Mesozoic clastic rocks are mainly exposed on the earth's surface, and its geomorphology is dominated by corrosion and erosion landforms. The dating results show that most of the structures in northwest Guangxi are middle Pleistocene active faults, and the movement mode is mainly stick-slip. According to the seismogeological research results of the eastern part of the Chinese mainland, the active faults of the middle Pleistocene have the structural conditions for generating earthquakes of about magnitude 6. In the northwest Guangxi, the crustal dynamic environment and geological structure are closely related to Sichuan and Yunnan regions. Under the situation that magnitude 6 earthquakes occurred successively in Sichuan and Yunnan region and magnitude 7 earthquakes are poised to happen, the risk of moderately strong earthquakes in the northwest Guangxi region cannot be ignored. Based on the analysis of deep structure and geophysical field characteristics, it is concluded that the Tian'e-Nandan-Huanjiang area in the northwestern Guangxi is not only the area with strong variation of the Moho surface isobath, but also the ML3.0 seismic gap since September 2015, and the abnormal low b value area along the main fault. Regions with these deep structural features often have the conditions for moderately strong earthquakes. The paper systematically analyzes the spatial and temporal distribution features and mechanism of regional gravitational field and horizontal crust movement and further studies and discusses the changes of regional gravitational field, crustal horizontal deformation and interaction between geologic structure and seismic activity based on 2014-2018 mobile gravity measurements and 2015-2017 GPS observation data in the northwestern Guangxi. The results show that:1)On July 15, 2017, a MS4.0 earthquake in Nandan happened near the center of four quadrants of changes of gravity difference, and the center of abnormal area is located at the intersection of the Mulun-Donglang-Luolou Fault, the Hechi-Nandan Fault and the Hechi-Yizhou Fault. The dynamic graph of differential scale gravitational field reflects the gravity changes at the epicenter before and after the Nandan earthquake, which is a process of system evolution of "local gravity anomaly to abnormal four-quadrant distribution features → to earthquake occurring at the turning point of gravity gradient zone and the zero line to backward recovery variation after earthquake". Meanwhile, according to the interpretation of focal mechanism of the Nandan earthquake, seismogram and analysis of seismic survey results, the paper thinks that the four-quadrant distribution of positive and negative gravity, which is consistent with the effect of strike-slip type seismogenic fault before Nandan earthquake, demonstrates the existence of dextral strike-slip faulting; 2)The pattern of spatial distribution of gravitational field change in northwestern Guangxi is closely related to active fault. The isoline of cumulative gravity generally distributes along Nandan-Hechi Fault and Hechi-Yizhou Fault. The gravity on both sides of the fault zone is different greatly, and gradient zone has influences on a broad area; the spatial distribution of deformation field is generally featured by horizontal nonuniformity. Tian'e-Nandan-Huanjiang area is located at the high gradient zone of gravity changes and the horizontal deformation surface compressional transition zone, as well as near the intersection of Hechi-Yizhou Fault, Hechi-Nandan Fault and Du'an-Mashan Fault; 3)The geometric shape of gravitational field in northwestern Guangxi corresponds to the spatial distribution of horizontal crustal movement, which proves the exchange and dynamic action of material and energy in the region that cause the change and structural deformation of fault materials and the corresponding gravity change on earth's surface. The recent analysis of abnormal crustal deformation in northwestern Guangxi shows that Tian'e-Nandan-Huanjiang is a gradient zone of abnormal gravity change and also a horizontal deformation surface compressional transition zone. It locates at the section of significant change of Moho isobaths, the seismicity gap formed by ML3.0 earthquakes and the abnormal low b-value zone. According to comprehensive analysis, the region has the risk of moderately strong earthquake. 相似文献