Distribution and structural characteristics of the Xi'an Section of the Weihe Fault     

师亚芹  冯希杰  戴王强  任隽  李晓妮  韩恒悦 《地震学报(英文版)》2008,21(6):636-651

The results of seismic deep reflection,high resolution refraction and shallow artificial seismic exploration indicate that the fault on the northern bank of the Weihe river is composed of two faults,one is the Yaodian-Zhangjiawan fault and the other is the Chuanzhang-Zuitou fault.The 22 km long Yaodian-Zhangjiawan fault of EW-striking starts from Chenjiagou via Yaodian town,Qianpai village,Bili village,Wujia town and Zhangjiawan to Jiajiatan.The 15 km long Chuanzhang-Zuitou fault striking near EW starts from Chuanzhang via Mabei to Zuitou.The Weihe fault offset the basement and upper crust,the reflecting layers of TQ,TN,TE and Tg are ruptured at depth of about 15 km.In the deep part,the Weihe fault and the secondary fault form a Y-shaped structure or a synthetic low angle intersection.The Weihe fault is a listric normal fault.The fault has obvious structural characteristics of a reversed-drag normal fault and a normal drag normal fault with the depth of 1 000 m,and also has the characteris-tics of syngenetic sediment.The Weihe fault is one of the faults which control the basin sediment,and it is the boundary fault of Xi’an depression and Xianyang salient.The depth of the fault decreases from the west to east gradually,the deep part intersects with the Lintong-Chang’an fault at the intersection part of Weihe River,Jinghe River and Bahe River and the shallow part connects with the Weinan-Jingyang fault.The seismic exploration re-sults indicate that no fault exists on southern bank of the Weihe River.  相似文献   

Erosion and terrace failure due to agricultural land abandonment in a semi‐arid environment     

J. P. Lesschen  L. H. Cammeraat  T. Nieman 《地球表面变化过程与地形》2008,33(10):1574-1584

Agricultural land abandonment is currently widely spread in Mediterranean countries and a further increase is expected. Previous research has shown that abandoned fields in semi‐arid areas are more vulnerable to gully erosion. The absence of ploughing and slow vegetation recovery cause the formation of soil crusts with low infiltration rates, resulting in increased runoff and gully erosion risk. The objective of our study was to assess the extent and causes of erosion and terrace failure on abandoned fields and to discuss options for mitigation. The study was carried out in the Carcavo basin, a semi‐arid catchment in southeast Spain. At catchment scale all abandoned fields were surveyed and characteristics of each field were described. Additionally we surveyed abandoned and cultivated terraces and used statistical analyses to determine the factors that induce terrace failure. At field scale we constructed a detailed digital elevation model (DEM) for an abandoned terrace field in order to calculate sediment losses since time of abandonment. The results revealed that more than half the abandoned fields had moderate to severe erosion and the statistical analysis showed that these fields had significantly steeper slopes, were terraced and had cereals as previous land use. Factors that increase the risk of terrace failure were land abandonment, steeper terrace slope, loam texture, valley‐bottom position and shrubs on the terrace wall. The reconstructed erosion rate (87 ton ha^?1 year^?1) confirmed the importance of gully erosion on these abandoned terrace fields. Potential soil and water conservation practices to mitigate soil erosion after abandonment are: (1) maintenance of terrace walls, as a result more water is retained, which increases vegetation cover and consequently decreases erosion. (2) Revegetation with indigenous grass species on spots with concentrated flow, especially near terrace walls. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

气候变化对渭河上游径流量和输沙量的影响   总被引：17，自引：2，他引：15  

邓振镛  张强  李栋梁  朱拥军  董安祥  张毅 《中国沙漠》2006,26(6):982-985

利用渭河上游北道水文站的径流量和输沙量资料和渭河上游流域16个气象站的气象资料,分析了1951—2000年期间气候变化对渭河上游径流量和输沙量的影响。结果表明:渭河上游径流量变化总体呈下降趋势,跃变点发生在1967年,20世纪60年代径流量最大,90年代以后径流量最小。径流量的变化主要取决于流域降水量的变化。葫芦河支流流域的降水量对径流量变化的影响最为敏感,其次是榜沙河支流流域的降水量。输沙量的多少主要取决于上游降水量的多少和大雨的次数,其次是风速大小和大风次数的多少。  相似文献   

潍河口水文特征分析     

董礼先  苏纪兰  陈琪  陈耕心 《海洋学报》2000,22(2):9-15

根据1997年和1998年两次潍河河口水文调查资料分析了潍河河口的水文特征及建闸截流的影响。结果说明,潍河是一个M₂潮占主导地位的不规则半日潮弱潮河口。上游建闸截流使得河口5、6月份的水温降低而盐度增高,并减少了口门内重力环流的出现机率。  相似文献   

利用地理信息系统进行海岸阶地确定与对比──以辽东半岛大连东北海岸为例   总被引：2，自引：2，他引：0  

邬伦  刘岳峰  韩慕康 《海洋学报》2000,22(2):71-78

海岸阶地的确定与划分对比对区域研究与应用有重要意义,然而传统的野外测绘方法劳动强度大、耗时多、效率低,而且有许多局限性。结合地貌原理,利用地理信息系统技术,建立了阶地分析模型方法与处理流程,并以辽东半岛大连附近地区为实验区进行了试验分析与机助制图。对比结果表明,该新方法具有节省人力和物力、精度和效率高、可视化效果直观、全面等特点,能使阶地研究达到新的深度。  相似文献   

The role of neotectonics and glaciation on terrace formation along the Nysa K odzka River in the Sudeten Mountains (southwestern Poland)     

Dariusz Krzyszkowski  Bogus aw Przybylski  Janusz Badura 《Geomorphology》2000,33(3-4)

The Nysa K odzka river drainage basin in the Sudeten Mts., SW Poland, preserves a complex late Cainozoic succession that includes eight fluvial series or terraces and deposits from two glacial episodes as well as local volcanic rocks, slope deposits and loess. Fluvial sedimentation took place during the Late Pliocene and from the early Middle Pleistocene (Cromerian), with a long erosion phase (gap) during the Early Pleistocene. Fluvial series are dated to the Late Pliocene, Cromerian, Holsteinian, late Saalian/Eemian, Weichselian, and the Holocene. Glacial deposits represent the early Elsterian and early Saalian stages. Almost all these stratigraphic units have been observed in all geomorphic zones of the river: the mountainous K odzko Basin, the Bardo Mts. (Bardo gorge) and in the mountain foreland. The main phase of tectonic uplift and strong erosion was during the Early Pleistocene. Minor uplift is documented also during the post-early Saalian and probably the post-Elsterian. The post-early Saalian and post-Elstrian uplift phases are probably due to glacio-isostatic rebound. The Quaternary terrace sequence was formed due to base-level changes, epigenetic erosion after glaciations and neotectonic movements. The Cromerian fluvial deposits/terraces do not indicate tectonic influence at all. All other Quaternary terraces indicate clear divergence, and the post-early Saalian terraces also show fault scarps. The fluvial pattern remained stable, once formed during the Pliocene, with only minor changes along the uplifted block along the Bardo gorge, inferring an antecedent origin for the Bardo gorge. Only during the post-glacial times, have epigenetic incisions slightly modified the valley.  相似文献   

渭河谷地晚新生代地表环境巨变的孢粉记录   总被引：3，自引：0，他引：3  

童国榜  吴锡浩 《地质力学学报》2000,6(4):11-18

本文在总结渭河谷地２０多个孢粉剖面的基础上,依据古地磁资料确定其时代,并在空间和时间上进行孢粉组合对比,从而建立了１０个区域孢粉组合带。由此提出３．５ＭａＢＰ以来孢粉植物群的演化经历了５个阶段：由阔叶林－－针叶林－－森林草原与草原－－森林草原与茺漠草原－－草原－－森林草原与草原。这５个阶段标志着地表环境系统发生巨大变革,变革时间为２．５ＭａＢＰ,２．０ＭａＢＰ,１．４／１．６ＭａＢＰ和０．８ＭａＢ  相似文献   

青海黄河贵德段河流阶地及新构造运动研究     

苗琦  李丽松  钱方  赵志中 《地质与资源》2012,21(5):493-496

贵德盆地作为青藏高原东北部的一个构造地貌单元,盆地中河流阶地发育,但是阶地的形成时代仍存在很大争议.选择阶地作为研究对象,并从龙羊峡至松坝峡共采集阶地样品10个,进行ESR测年,对测试结果进行了分析研究,建立了T0-T4阶地的海拔、河拔高度序列,分析了贵德盆地新构造运动规律具有间歇性、差异性、不对称性特征.  相似文献   

渭河断裂咸阳段活动性研究   总被引：1，自引：0，他引：1  

田勤虎  段蕊  李晓妮  卞菊梅  魏青珂 《地震研究》2015,38(2):250-256,333

通过地貌追踪、浅层地震、钻孔联合剖面勘探及探槽开挖等,查明了渭河断裂咸阳段(杨家村—窑店)的展布和最新活动时代。结果表明,渭河断裂咸阳段从咸阳市北侧渭河阶地前缘陡坎通过,考虑到断裂在金家庄、东耳村一带存在一个左阶斜裂区,阶区宽约1 km,可将断裂分为东、西两段,即:杨家村—金家庄段和东耳村—窑店段。断裂总体走向NE,倾向S,倾角65°~75°,为同生正断层。程家村探槽显示断裂错断全新统黑垆土底界15 cm,该层底界14C测年结果为2 255 BP,顶界光释光(OSL)年龄测年结果为(3.7±0.41)ka,说明断裂在全新世有活动。渭河断裂咸阳段自晚更新世以来活动性逐渐减弱,全新世平均活动速率为0.04~0.12mm/a。  相似文献   

基于MOD16数据的渭河流域地表实际蒸散发时空特征   总被引：4，自引：0，他引：4  

位贺杰  张艳芳  朱妮  王鹏涛  喻元 《中国沙漠》2015,35(2):414-422

基于流域水量平衡法,利用水文数据和气象数据对渭河流域MOD16-ET(实际蒸散发)数据进行精度验证; 利用2000-2012年MOD16-ET数据和GIS技术定量分析了渭河流域(分为干流、泾河、北洛河3个子流域)地表实际蒸散发年际和年内的时空变化特征。结果表明:(1) 3个子流域的实测降水空间插值结果与MOD16-ET估算结果比较,相对误差平均值为8.36%,渭河干流误差较小,其他2个子流域误差相对较大; (2) 3个子流域上游至下游的ET剖面线变化不同,明显受地表覆盖类型影响; (3) ET值年内分布大致呈单峰型格局,季节变化特征为夏季(177.14 mm)> 秋季(105.22 mm)> 春季(92.97 mm)> 冬季(77.50 mm); (4) 基于栅格尺度的ET值年际变化特征空间分布,各子流域下游以降低趋势为主,渭河中游和上游以升高趋势为主,北洛河、泾河中游和上游以基本不变趋势为主,具体影响因素的定量分析仍需MODIS资料的时间累积。  相似文献