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871.
872.
围绕区域发展潜力来源,建构了区域发展潜力影响要素分析框架,论述了外部环境、内部资源、内部能力的组成及其影响机理。得出:区域发展阶段不同,区域发展潜力影响因素的类型与质量存在分异。且不同发展阶段下发展潜力主导影响因素呈现:(1)处于农业经济主导和工业化初期的区域,受控于自然资源与条件、人口与劳动力;(2)处在工业化中、末期的区域,主导因素是区域经济基础、人力资本和发展战略;(3)处在后工业化和信息时代的区域,区域能力是其主导因素。 相似文献
873.
粘性土在不同温度下龟裂的发展及其机理讨论 总被引:5,自引:0,他引:5
通过试验,研究了粘性土在不同温度下龟裂的发生和发展规律,运用计算机图像处理和编程技术,对不同温度下获得的粘性土龟裂网络的几何结构和形态特征进行了定量分析。结果表明:龟裂的发展过程可分为四个阶段,温度效应十分明显。温度越高,龟裂形貌越简单,龟裂条纹越宽,而在较低的温度下,龟裂的形貌比较复杂,龟裂条纹纤细且间距较密,表面比较破碎;从粘土矿物双电层理论对龟裂的形成机理提出了一种新的解释;在试验中还发现了一个十分有趣的现象,即大部分龟裂都呈垂直或近似垂直相交,被龟裂分割出的区块形状多以四边形为主,其它多边形较少;最后提出了龟裂研究的下一步课题。 相似文献
874.
江苏里下河地区洪涝灾害演变趋势与成灾机理分析 总被引:4,自引:0,他引:4
江苏里下河地区是相对封闭的水网地区,洪涝频繁。研究该地区洪涝演变趋势和成灾机理对区域防洪减灾具有重要意义。里下河地区洪涝演变趋势表现在洪涝类型的多样性,高水位日益频繁、高水位发生机率加大,致灾暴雨频率增大等方面。在自然成因方面,流域暴雨是成灾的主要原因,锅底洼的形态是洪涝发生的地貌大背景,水系的复杂格局也加剧了洪涝的程度和频度。在人类活动方面,不合理的圩垸垦殖导致湖荡萎缩,减弱了水体调蓄能力;闸坝建设引起河道淤积、排涝能力降低致使洪水位趋高;城镇化改变下垫面性质的水文效应也是洪涝频繁的主要因素。 相似文献
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876.
The temporal and spatial distribution characteristics of earthquakes in the Ordos block are studied by using historical earthquake data,instrument data of the regional seismic network around the Ordos block and the historical felt earthquake data,and the relationship between seismicity in the Ordos block and seismicity around the Ordos block is discussed. The result shows that the Ordos block is a typical moderate-strong earthquake active region where many M_S≥5.0 destructive earthquakes have occurred. The temporal and spatial distribution of earthquakes in the Ordos block is asymmetrical. The temporal distribution of earthquakes shows a periodic characteristic and the activity of earthquakes in the southeastern Ordos block is higher than in the northwest Ordos block. The M_S≥5.0 moderate size earthquakes in the Ordos block are controlled by the M_S≥6.0 earthquake around the Ordos block. 相似文献
877.
The M8.0 Wenchuan earthquake occurred on the Longmenshan fault zone. Based on field investigation of the surface rupture and focal mechanism study of the aftershocks, we discuss the geological relationship of the main, secondary and triggered ruptures. The main rupture is about 200km long and can be divided into the south part and the north part. The south part consists of two parallel fault zones characterized by reverse faulting, with several parallel secondary ruptures on the hanging wall of the main fault, and the north part is a single main fault zone characterized by lateral strike-slip and reverse faulting. Compared to a 300km long aftershock distribution, the surface rupture only occupies 200km, and the remaining 100km on the northeast of the main rupture was triggered by aftershocks. Study on the ruptures of this earthquake will be useful for studying the earthquake risk evolution on the Longmenshan fault system. 相似文献
878.
879.
880.
Variability in rainfall threshold for debris flow after the Chi-Chi earthquake in central Taiwan, China 总被引:6,自引:0,他引:6
The purpose of this study is to analyze variability in rainfall threshold for debris flow (critical rainfall for debris flow triggering) after the ML 7.3 Chi-Chi earthquake in central Taiwan in 1999. Two study sites with different geological conditions were surveyed in the earthquake area. Streambed surveys were conducted to continuously monitor debris flows between 1999 and 2006. During the 7-year study period, every debris flow event was identified, and the streambed characterized. Results show that the rainfall threshold for debris flow was remarkably lower just after the Chi-Chi Earthquake, but gradually recovered. To date, this rainfall threshold is still lower than the original level prior to the earthquake. This variability in rainfall threshold is closely related to the mount of sediment material in the initiation area of debris flow, which increased rapidly due to landslides resulting from the earthquake. With the increase in sediment material, the rainfall threshold was lowered severely during the first year following the Chi-Chi earthquake. However, heavy rainfalls mobilized the sediment material, causing debris flows and transporting sediment downstream. With the decrease in sediment material, the rainfall threshold recovered gradually over time. Furthermore, debris flows occurred only in the subbasins that had sufficient sediment material to cause significant movement. Hence, these results confirm that the sediment material in the initiation area of debris flow is a crucial component of the rainfall threshold for debris flow. 相似文献