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81.
以泗水县为研究区,选取区域地貌、地质构造、地层岩性及人类工程活动等9个评价因子,基于GIS数据分析功能,运用信息量法及层次分析法确定各评价因子信息量及权重,进行地质灾害易发性评价。研究表明: 区域地貌低山区,坡度28°~65°,坡向西和西北,较坚硬的中厚层状碎屑岩、页岩、砂岩夹灰岩岩组,降雨量700~730 mm 及地震加速度0.10 g的区域内信息量最大; 各评价因子权重从大到小依次为区域地貌(0.21)、降水(0.16)、坡度(0.14)、地层岩性及人类工程活动(0.10)、坡向(0.09)、地质构造及地震(0.07)、水系(0.06); 研究区高易发区面积为294.26 km2,面积占比26.30%,灾害点数量占比84.62%,中易发区面积为66.28 km2,面积占比5.92%,灾害点数量占比15.38%,低易发区面积为758.42 km2,面积占比67.78%。对易发性评价过程的合理性进行检验,3个构造矩阵的随机一致性比率CR分别为0.000、0.013、0.020,均小于0.1,表明易发性研究结果具有合理性,能够为研究区地质灾害防治、土地利用规划及地质环境保护提供基础依据。 相似文献
82.
YUAN Liming;TIAN Fenglin;XU Suqin;ZHOU Chun;CHEN Jie 《海洋湖沼学报(英文)》2021,39(6):2153-2166
The Kuroshio Extension (KE) is one of the most eddy-energetic regions in the global ocean. However, most mesoscale eddy studies in the region are focused on surface eddies and the structure and characteristics of three-dimensional (3-D) eddies require additional research. In this study, we proposed a 3-D eddy identification and tracking algorithm based on pressure anomalies, similar to sea level anomalies (SLAs) for surface eddy identification. We applied this scheme to a 5-year (2008–2012) high-resolution numerical product to develop a 3-D eddy dataset in the KE. The reliability of the numerical product was verified by the 5-year temperature/salinity hydrological characteristics and surface eddy distribution. According to the 3-D eddy tracking dataset, the number of eddies decreased dramatically as the eddy existence-time increased and more anticyclonic eddies (AEs) had an existence-time longer than 1 week than cyclonic eddies (CEs). We presented daily variations in the 3-D structure of two 3-D eddy-tracking trajectories that exhibit a certain jump in depth and a shift toward the west and equator. In addition to the bowl, lens, and cone eddies that have been discovered by previous researchers, we found that there is a cylindrical eddy, and its eddy radii are almost consistent across all layers. CEs cause significant negative temperature anomalies, \"negative-positive\" salinity anomalies, and sinking current fields in the KE region, while AEs cause positive temperature anomalies, \"positive-negative\" salinity anomalies, and upward current fields. The four types of eddies have different effects on the temperature/salinity anomalies and current field distribution which are related to their structure. 相似文献
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在海洋油气勘探这一过程中,震源设计是关键环节,其性能的优劣直接影响采集信号的质量。气枪以其质量可靠、组合灵活、安全环保等优势成为海洋勘探领域应用最广泛的激发震源,然而,随着勘探环境的复杂化,平面阵列的激发子波难以满足高分辨率勘探需求。因此,在立体阵列的基础上,分析不同容量气枪子波信号与时间关系,通过优化沉放深度,使不同容量单枪激发产生的振幅在接收时同相叠加,达到拓宽频带和压制陷波效应,进而改进震源的性能。将优化的立体阵列与常规阵列进行属性对比,证明宽频立体气枪阵列拥有更强的振幅能量和更宽的有效频带,可明显压制陷波效应,对复杂地质目标有较好的识别效果。 相似文献
85.
本文提出了一种基于Dempster-Shafer证据理论的风暴潮灾害损失评估方法。鉴于风暴潮致灾过程中的不确定性, 选择合适的具有代表性指标(包括最大风暴潮增水、最大有效波高和防灾减灾能力)产生灾害损失评估的证据, 并根据所选指标和风暴潮直接经济损失之间的相关性大小确定证据权重, 最后采用改进的Murphy证据融合算法进行证据融合, 从而判断灾害损失等级。通过实证分析发现, 本文所提出的方法在判断风暴潮灾害损失等级上的正确率达到93.1%, 优于朴素贝叶斯、支持向量机、神经网络和决策树等常用方法, 同时本文方法计算简便, 且随着训练集样本量的增加, 损失评估结果可进一步精细化。 相似文献
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PDC钻头在石油钻井和地质钻探中,在中等硬度和部分硬地层中钻进时,取得了很好的钻进效果,得到了满意的技术经济指标,生产单位也比较欢迎。但是,在复杂地层,如深孔软硬互层、裂隙互层和研磨性地层中钻进时,机械钻速变慢,钻头进尺降低,成了推广使用的“拦路虎”。俄罗斯钻探工作者针对上述地层钻探中存在的问题,设计出了加长型防斜减振钻头,经过实验室和野外试验证明,这种钻头是有效的,取得了很好的技术经济效果。 相似文献
88.
为揭示罗布泊盐湖第四系潜在物源区及凹陷阶段性演化过程,本文对罗布泊第一口钾盐科探深钻LDK01孔更新统不同深度样品进行碎屑锆石U-Pb微区定年分析。Th/U比值显示,钻孔碎屑锆石类型主要为岩浆锆石,少量为变质成因锆石。锆石年龄主要集中在209~240Ma、265~304Ma、320~385Ma、406~446Ma、705~880Ma及2376~2405Ma几个区间。综合分析潜在物源区的岩石属性和年龄构成,初步认为罗布泊地区前寒武纪年龄来自北部山前库鲁克塔格地区,加里东期碎屑锆石可能来源于阿尔金造山带和(或)南天山构造带。276Ma的峰值记录了塔里木盆地二叠纪大火成岩省事件,南天山最有可能为主导物源区。印支期和新生代碎屑锆石年龄暗示了北山地块和东天山,甚至较远的帕米尔-西昆仑山等地可能也提供了物源。凹陷周缘富钾岩体广泛出露,经风化、淋滤搬运至罗布泊,为凹陷第四纪成钾提供了有利的物质来源。塔里木盆地内部流域带来的碎屑组分是主要的物质来源,近源地区造山带岩体提供的物源有限。碎屑锆石年龄纵向变化特征显示,罗布泊北部地区在中更新世发生一次明显的构造抬升,可能是导致罗北凹地形成的重要原因。 相似文献
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Ultra-high pressure(UHP)eclogites that derive from subducted oceanic crust are rarely found at the Earth’s surface because they need to be enclosed in a buoyant host rock such as serpentinites that facilitate exhumation(Hermann et al.,2000;Guillot et al.,2001).Under normal subduction geotherms,serpentinites break down just before UHP conditions are reached and therefore most of the exhumed eclogites representing subducted oceanic crust formed under fore-arc conditions.We investigated eclogite blocks enclosed into serpentinites that occur in the southwestern Tianshan oceanic subduction,China.A previous study proved that the serpentinites derive from altered oceanic crust and experienced UHP metamorphism at low temperatures of 510-530°C(Shen et al.,2015).Three relatively fresh eclogite samples were studied in detail.Sample 129-7 shows the retrograde mineral assemblage of amphibole+biotite+albite+chlorite+minor titanite and peak metamorphic relics of omphacite+garnet±chlorite.Sample C107-23 is mainly composed of amphibole+albite+chlorite+zoisite+muscovite+minor titanite as a retrograde assemblage and garnet+phengite as the peak metamorphic relics with omphacite only found as inclusions in garnet.Similar to sample C107-23,sample C11066 preserves large-grained euhedral to subhedral garnet relics with omphacite inclusions,and epidote,diopside,amphibole,muscovite,chlorite,albite and biotite are in the matrix belong to the retrograde assemblage.These three retrograde eclogite samples were modelled using thermodynamic calculations in the Mn NCKFMSHO(Mn O-Na_2O-Ca O-K_2O-FeO-Mg O-Al_2O_3-SiO_2-H_2O-Fe_2O_3)system.Based on the peak assemblage of omphacite+garnet and the crossing of the grossular and pyrope isopleths in garnet,peak P-T conditions of~460-470oC,28-29 kbar(129-7),450-500oC,28-35 kbar(C107-23),~475-505oC,26-29 kbar(C11066)were calculated.The retrograde assemblages indicate near isothermal decompression resulting in a clockwise P-T evolution of these eclogites.The peak metamorphic pressures at 500°C are well within UHP conditions(coesite stability field)and are within error the same as peak conditions of the host serpentinites(Shen et al.,2015).This provides evidence that eclogites and serpentinites shared the same evolution.We infer that the subducted low-density serpentinites were assembled with the high-density eclogites during subdution and helped the latter to exhume back to the surface.The studied eclogites thus represent rare examples of relics of oceanic crust that was subducted to sub-arc depth. 相似文献