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高山峡谷区是滑坡灾害频发地区,随着气候变化和人类活动加剧,滑坡呈多发、频发态势。本文选择坐落于横断山高山峡谷区的西藏江达县作为研究区,利用野外调查获取的85个滑坡数据,选取坡度、河流密度、地貌类型、降水量、距断层距离、道路密度、地震动峰值加速度、岩性等8个稳定性影响因素,运用地理探测器对滑坡稳定性的影响因素进行了探测。结果表明:(1)按滑坡体体积划分等级,江达县滑坡主要以中、小型滑坡为主;按其稳定性划分,50%以上的滑坡处于稳定状态;按危险等级划分,以Ⅲ级、Ⅳ级为主;江达县滑坡主要沿河流与道路分布,全县地面调查发现85处滑坡全部分布于河流附近,其中71.76%的滑坡分布于道路两侧。(2)江达县滑坡稳定性的主要影响因子为地貌类型、河流密度、道路密度和距断层距离,其贡献率分别为0.501,0.477,0.465,0.332;当影响因子两两相互作用时,因子解释力总是大于单个因子对滑坡稳定性的解释力,即当两种影响因子相互作用时,对于滑坡的失稳具有促进作用。 相似文献
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临界起沙阈值可表征地表土壤的可蚀性,是风蚀起沙研究中非常重要的物理量之一。基于微气象学方法,将沙尘浓度和垂直沙尘通量均开始增加且至少持续0.5 h所对应的摩擦速度(或风速)确定为临界起沙摩擦速度u*t(或临界起沙风速Ut)。利用内蒙古科尔沁沙地地区2010-2013年春季大气环境综合观测资料,分析了不同沙尘天气过程(扬沙、沙尘暴和强沙尘暴)起沙阶段沙尘浓度和垂直沙尘通量随摩擦速度的演变特征,精细确定了该地区临界起沙摩擦速度(u*t)和临界起沙风速(Ut)的范围分别为0.45±0.20和6.5±3.0 m/s,同时讨论了不同起沙判据对确定临界起沙阈值产生的影响。相比而言,采用的起沙判据尽可能地排除了沙尘输送和沉降过程的影响,适用于不同的沙尘天气类型,使沙尘粒子进入大气的起沙结果更趋于合理,其结果可为建立统一、合理的起沙判据提供参考。 相似文献
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Neogene Paleoseismic Events and the Shanwang Biota’s Burial in the Linqu Area, Shandong Province, China 总被引:2,自引:0,他引:2
Several paleoseismic events are recorded in the Neogene Linqu Group, exposed in the Linqu area, Shandong Province, China. The events were interpreted on the basis of fieldwork and laboratory analysis, which showed the presence of seismites with plastically deformed soft-sediment deformation structures in the Shanwang Formation, and of seismic volcanic rocks in the Yaoshan Formation which show brittle deformation. The earthquake-triggered soft-sediment deformations in the seismites include load structures, ball-and-pillow structures, flame structures, pillow-like beds, boudinage structures, slump folds, syn-depositional faults, veins of liquefied sand, and dikes of liquefied sandy lime-mud. The seismic activity is also reflected in what might be called ‘brittle seismites'; these originated when, under the influence of seismic vibrations, semi-consolidated conglomerate was shattered. Moreover, volcanic activity is related to intense earthquakes that affected basalts intercalated with sand layers; these successions are known as ‘seismic volcanic rocks', which are characterized by veins of liquefied sand intruding the basalts. All above traces of paleoseismic activity were left from one single time span of 4 Ma with active seismicity that took place 14–10 Ma. This time span is known as ‘the Linqu Neogene Paleoseismic Active Period', which is divided into four paleoseismic episodes, which were responses to tectonic extension and basin rifting in this area. It even includes the activity of the Yishu Fault Zone during the Miocene and the Neogene. The ratios of trace elements in the seismites, w(La)/w(Sc) and w(La)/w(Th) are higher than the average value of the upper crust, but w(Th)/w(Sc) is lower; this is geochemical evidence for the basin rifting that resulted in a high sedimentation rate. The intense and frequent paleo-earthquakes are held responsible for the rapid burial of the Shanwang Biota. Secondary earthquake-induced processes(e.g. slumping of a lake shore and the strongly increased lacustrine sedimentation rate) contributed to the rapid burial of the biota. 相似文献
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为应对河道洪峰流量增大和漫溃堤长历时相伴发生的洪灾现象,借鉴全二维气相色谱理论提出全二维水动力模型概念,建立了模拟河道和灌区洪水演进的漫溃堤洪水联算全二维水动力模型,并采用Roe格式的近似Riemann解对界面通量进行数值求解。模型内通过漫溃堤堰流公式成功实现河道与灌区的耦联,考虑溃口展宽变化,加密处理河道网格,采用热启动与干湿水深理论对模型进行优化,并利用加大糙率法对村庄较为密集的地形进行优化处理,尽可能反应地面真实情况。将该模型应用于黄河宁蒙段河道与左右岸灌区的漫溃堤洪水演进模拟,计算结果合理可靠,流场分布均匀光滑,初步验证了模型的精度及可靠性,研究成果对河道溃决洪水的精细仿真模拟和该地区洪水风险分析决策具有重要意义。 相似文献
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基于对流参数的雷暴潜势预报研究 总被引:14,自引:1,他引:14
为提高雷暴天气的潜势预报能力,在统计分析安徽省雷暴形成天气条件的基础上,利用2003-2004年T213资料,选取与雷暴相关性好的对流参数作为预报因子。并在考虑因子季节变化特征的基础上,分别用判别分析法和指标叠加法制作雷暴潜势预报,结果表明指标叠加法优于判别分析法。最后用指标叠加法试报了2005年3—8月的雷暴,临界成功指数CSJ=69.4%,命中率POD=89.5%,虚假报警率FAR=24.4%,分区预报准确率也较高。另外,试报期间的区域性冰雹、雷雨大风全部命中,可见该方法对冰雹、雷雨大风也有较好的指示意义。 相似文献
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The Southern Yellow Sea Cold Water Mass(YSCWM) is closely related to the modern circulation system of the east China shelf seas, which has significantly influenced regional marine environmental changes. The study of the Holocene evolution of the YSCWM will greatly improve our understanding of the mechanisms of regional environmental change. Benthic foraminifera are sensitive to bottom water environmental changes and can serve as useful indicators in bottom water environmental reconstruction. In this study, benthic foraminifera were analyzed in core N02 from the northwestern margin of the southern Yellow Sea Mud to decipher the phase evolution of the YSCWM during the last 7 kyr. Benthic foraminifera census counts and Q-mode factor analysis indicate that the Holocene sedimentary environment can be divided into three stages: From6.9–5.0 ka, the fauna was dominated by Ammonia ketienziensis, indicating that the YSCWM was at its strongest during the last 7 kyr, while the Yellow Sea Coastal Current(YSCC) had a weak influence on the bottom water of the study area. From 5.0–2.9 ka,the relative abundance of Hanzawaia nipponica remarkably increased while the abundance of A. ketienziensis decreased significantly, reflecting that the strength of the YSCWM was relatively weak and the range of the YSCWM might have contracted. The influence of the YSCC on the bottom water might have slightly increased, although its influence was still weak during this time. A notable increase in low-temperature and low-salinity species, such as Protelphidium tuberculatum and Buccella spp. has occurred since 2.9 ka, indicating that the YSCC has had a strong influence on bottom water during this period,while the strength of the YSCWM has been at its weakest during the last 7 kyr. Generally, the influence of the YSCWM and the YSCC on the bottom water properties of the study area show an obvious seesaw pattern, with one's influence increasing while the other's influence decreases and vice versa. The fluctuations in the strength of YSCWM during the Holocene may be caused by the different effect allocations of regional climatic factors(i.e. El Ni?o Southern Oscillation, East Asian Winter Monsoon,summer insolation in the northern hemisphere, etc.) acting on the circulation system during different periods. 相似文献
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