射线法模拟分析井间地震观测的波场特征   总被引：2，自引：1，他引：1       下载免费PDF全文

李桂花  朱光明 《地球物理学进展》2007,22(6):1847-1855

按照井间地震的观测系统,用改进的突变点加插值射线追踪方法,追踪每炮每道的射线路径,计算几种主要类型的波沿射线路径的波至时间和射线振幅,制作井间地震多炮多道水平分量和垂直分量的合成记录.并将合成记录选排为井间共炮点道集、共接收点道集、共偏移距道集和共中心深度点道集,系统地分析了不同道集内几种主要类型的地震波的传播特征.对野外观测的实际井间地震记录进行了模拟,从复杂的井间地震记录中,识别出井间地震实际观测到的不同类型的波场,为随后的井间地震资料处理和应用提供了依据.  相似文献   

干旱风沙区植被重建初期对土壤微生物群落结构的影响          下载免费PDF全文

张力斌  何明珠  张克存  安志山  王金国  惠迎新  贾小龙 《干旱区地理》2022,45(6):1916-1926

为揭示干旱风沙区植被重建对土壤微生物群落结构的影响,以乌海至玛沁高速公路腾格里沙漠段生态防护体系的植被重建区土壤为研究对象,以流动沙丘为对照,运用高通量测序技术研究植被重建区土壤微生物群落结构随植被恢复重建的变化特征。结果表明:植被重建区与流沙区土壤微生物群落组成相似,均以放线菌门(58.53%～67.85%)、变形细菌门(16.53%～19.68%)等为优势类群;优势菌属包括诺卡氏菌属、甲基柔膜菌属、微红微球菌属和微枝型杆菌属。与流沙区对照相比,植被重建区显著增加了土壤大部分菌门相对丰度和多样性。植被恢复重建后土壤pH、电导率及盐分含量降低;土壤微生物量磷(MBP)、土壤微生物量碳(MBC)与土壤微生物量碳氮比(MBC:MBN)在植被重建区浅层土壤(0～5 cm、5～10 cm和10～20 cm)显著高于流沙区。因此,对于沙漠公路生态防护体系而言,植被重建能显著改善其浅层土壤养分状况、微生物相对丰度和多样性水平,是改善沙漠生态环境的重要措施。  相似文献   

大量采沙对东江下游及东江三角洲河床地形和潮汐动力的影响     

贾良文  罗章仁  杨清书  欧素英  雷亚平 《地理学报(英文版)》2007,17(2):197-211

The sand dredging and its impacts on riverbed evolution and tidal dynamic change in the lower reaches and delta of the Dongjiang River are examined in this paper. The large amount of sand, totally 3.32 billion m^3 from 1980 to 2002, was mined from the riverbeds of the lower reaches and delta of the Dongjiang River. Increasing of the channel capacity, lowering of the average riverbed elevation, deepening of the water depth and decreasing of the longitudinal riverbed gradient are the main effects on the riverbed evolution brought by the large amount of sand dredging. Under the strong sand dredging and associated significant riverbed deformation, the notable changes of the tidal dynamic in the lower reaches and delta of the Dongjiang River occurred, including： （1）in the upper reaches of the Dongjiang River delta and lower reaches of the Dongjiang River, tidal level dropped apparently, tidal range widened, flood tidal duration became longer, amplitudes for major tidal components became bigger and tidal dynamics intensified; （2） tidal wave spread faster; and （3） the limits of the tidal level, tidal current and salt water moved upstream.  相似文献   

Field measurements of influence of sand transport rate on structure of wind-sand flow over coastal transverse ridge   总被引：2，自引：0，他引：2  

Yuxiang Dong  S. L. Namikas  P. A. Hesp  Jun Ma 《中国地理科学(英文版)》2008,18(3):255-261

The structure of wind-sand flow under different total sand transport rates was measured with field vertical anemometer and sand trap on the crest of typical coastal transverse ridge in Changli Gold Coast of Hebei Province, which is one of the most typical coastal aeolian distribution regions in China and famous for the tall and typical coastal transverse ridges. The measurement results show that, on the conditions of approximate wind velocities and same surface materials and environments, some changes happen to the structure of wind-sand flow with the increase of total sand transport rate on the crest of coastal transverse ridge. First, the sand transport rates of layers at different heights in the wind-sand flow increase, with the maximum increase at the height layer of 4-8cm. Second, the ratios of sand transport rates of layers at different heights to total sand transport rate decrease at the low height layer （0-4cm）, but increase at the high height layer （4-60cm）. Third, the distribution of the sand transport rate in the wind-sand flow can be expressed by an exponential function at the height layer of 0-40cm, but it changes from power function model to exponential function model in the whole height layer （0-60cm） and changes into polynomial function model at the height layer of 40-60cm with the increase of total sand transport rate. Those changes have a close relationship with the limit of sand grain size of wind flow transporting and composition of sand grain size in the wind-sand flow.  相似文献   

黄河中新世未进入渤海湾盆地：来自碎屑锆石U-Pb年龄的约束     

林旭  刘海金  刘静  陈济鑫  李玲玲 《地质学报》2022,96(7):2506-2518

黄河是中国北方最大河流,其发育和形成对中国北部三大地势阶梯的建立具有重要指示意义。但到目前为止,有关黄河的形成时代存在较大争议。基于此,本文对鲁中山区的河流进行碎屑锆石U-Pb年龄分析(n=240),与流入渤海湾盆地的辽河、滦河、永定河、滹沱河、漳河和黄河的锆石U-Pb年龄进行对比,从而确定黄河因具有显著的新元古代峰值年龄(1000～700 Ma)成为渤海湾盆地的特征河流。本文将黄河下游的碎屑锆石U-Pb峰值年龄与渤海湾盆地中新统钻孔的锆石U-Pb峰值年龄进行对比,结合多维判别图(MDS),结果表明黄河在中新世未进入渤海湾盆地。  相似文献   

基于“3S”技术的南流江采砂点时空分布特征     

朱文轩  黎树式  冯炳斌  杨夏玲 《热带地理》2022,42(12):2076-2087

利用Landsat系列遥感数据,通过目视解译的方式分析了南流江近30年的采砂点的时空分布特征及其环境效应,并探讨其驱动因素。结果表明：南流江采砂点数量在1988—2008年快速上升,2018年的采砂点数量出现大幅下降;各时期均为下游采砂点最多,中游次之,上游最少。采砂点时空分布的主要驱动因素是流域的经济快速发展带来的城市化快速扩张,2018年采砂点数量下降的主要原因是相关部门加强对非法采砂活动的监管。采砂活动是南流江含沙量下降的重要原因之一,同时也是南流江水质下降的重要原因;采砂活动使得南流江采砂区域面积在1988—2018年总共减少了7.24 km²;目前河口三角洲岸线并没有因为采砂活动的加剧输沙量减少而发生明显的蚀退。  相似文献   

基于荧光素和图像追踪技术的冻融循环作用下土体水汽迁移量测装置系统研究     

程博远  张玉芝  王天亮  温安  尹赵爱 《冰川冻土》2021,43(1):322-330

寒区高铁路基中粗颗粒填料水汽迁移可能是路基冻胀变形的来源,直观追踪冻融循环作用下土体水汽迁移过程,有助于研究水分迁移规律,为冻胀机理提供理论依据.基于此,提出采用荧光素示踪和图像处理技术方法,直观观测土体中水汽迁移的规律.首先开展荧光素示踪、蒸发试验及图像处理技术的研究,证明示踪剂可实现冻结锋面及外界液态水迁移的追踪;...  相似文献   

古尔班通古特沙漠风沙土土壤蒸发特征   总被引：12，自引：2，他引：10  

翟翠霞  马健  李彦 《干旱区地理》2007,30(6):805-811

土壤表面蒸发是降水的无效损失,其大小直接决定着降水转化为有效土壤水的效率,从而间接决定了植物可利用水分的多寡。在降水稀少的沙漠区,定量认识土壤蒸发的大小和其所占降水的比例显得尤为重要。在2004年全生长期(5~9月)应用自制的微型蒸渗仪(Micro-Lysime-ter)测定了风沙土(有结皮覆盖的丘间低地和裸露沙丘顶部)和对照的荒漠盐碱土的土壤蒸发。结果表明:在相似的气象条件下,风沙土区的丘间低地和荒漠盐碱土的日平均蒸发量分别约是裸露沙丘(风沙土区)的2倍和3倍。整个生长期裸露沙丘的累积蒸发量为18.7mm,丘间低地为38.8mm,荒漠盐碱土为52.1mm。根据整个观测期的累积蒸发量和累积降雨量计算得出的蒸发降雨比分别为:裸露沙丘0.20,丘间低地0.42,荒漠盐碱土0.62,表明裸露沙丘由降水转化为土壤水而储存的比率最高。同时,从数据分析中可以看出:在风沙土区0~5cm土层的含水量对土壤蒸发起决定作用,而盐碱土区的土壤蒸发则受到更深层次土壤水分的影响。裸露沙丘低的土壤蒸发、高的降水转化效率,为植被恢复奠定了良好的基础。因此,裸露沙丘的低蒸发量可以视为植被状况对生态水文过程的一种良性反馈。  相似文献   

Effects of the anthropogenic activities on the morphological evolution of the Modaomen Estuary,Pearl River Delta,China   总被引：1，自引：0，他引：1  

贾良文  潘顺琪  吴超羽 《中国海洋工程》2013,27(6):795-808

Owing to the intensive human activities, the Modaomen Estuary has been significantly modified since 1950s, which has resulted in considerable changes of hydrodynamics and morphodynamics in the area. In this paper, the effects of the anthropogenic activities on the hydrodynamics and morphological evolution in the estuary at different stages are systematically assessed based on the detailed bathymetric data and field survey. The results show that the human activities have caused the channelization of the enclosed sea area in the Modamen Estuary;fast seaward movement of the mouth bar with high siltation;expansion of the channel volume due to channel deepening. The paper also highlights the main hydrodynamic changes in the estuary, including the rise of the water level;the distinguishing changes of tidal range before and after the 1990s （decrease and increase respectively）; as well as the increase of the divided flow ratio. It is found that reclamation is the main factor promoting the transition of nature of the estuary from runoff dominant to runoff and wave dominant, and sand mining activities are mainly to strengthen the tidal dynamic and to low the water level. The results provide useful guidance for better planning of the future developments in the estuary and further research in the area.  相似文献   

岛礁工程海水拌养珊瑚礁、砂混凝土修补与应用研究   总被引：1，自引：0，他引：1  

陈兆林  孙国峰  唐筱宁  柳玉良 《海岸工程》2008,27(4):60-69

对用海水拌养珊瑚礁、砂混凝土修补与抢修远离大陆的岛碾损坏工程进行应用研究和调研,对该种混凝土的原材料和物理力学性能进行检测,研究了修补界面剂的配合比与修补工艺以及操作方法,并进行了海水拌养珊瑚礁、砂混凝土与海水拌养普通混凝土修补的粘结强度对比测试和海水拌养快凝快强混凝土快速抢修的工程应用实践检验,为岛礁工程修补和抢修提供技术参考资料。  相似文献