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991.
根据某大坝右岸围堰爆破,对爆破地震波三维空间的频谱、加速度、速度、动力放大倍数进行了研究,得到爆破地震波在砼重力坝的不同高度、不同方向、不同介质中的反应特性。  相似文献   
992.
Glacial lakes and glaciers are sensitive indicators of recent climate change. In the Poiqu River basin of southern Tibet, 60–100 km NW of Mt. Everest, Landsat imagery defines post-1986 changes in the size and distribution of both glacial lakes and glaciers. Total area of glaciers in the 229-km2 drainage area has decreased by 20%. The number of glacial lakes with areas in excess of 0.020 km2 has increased by 11%, and the total area of glacial lakes has increased by 47%. The areas of typical large glacial lakes of the area (Galongco, Gangxico, and Cirenmaco) have increased by 104, 118, and 156%, respectively, and these increases are confirmed by field investigations.Comparing the 1986 data, the area of glaciers in the basin headwaters has decreased by 46.18 km2 to a present total area of 183.12 km2, an annual rate of change of 3.30 km2/year. Trends indicate that the total area of glaciers will continue to decrease and that both the numbers and areas of glacial lakes will continue to increase. Accompanying these trends will be an increased risk of debris flows, formed by entrainment of sediment in glacial-outburst floods and in surges from both failure and avalanche- and landslide-induced overtopping of moraine dams. Based on both the local and world-wide history of catastrophes from flows of these origins, disaster mitigation must be planned and appropriate engineering countermeasures put in place as soon as possible.  相似文献   
993.
Studies of interseismic strain accumulation are crucial to our understanding of continental deformation, the earthquake cycle and seismic hazard. By mapping small amounts of ground deformation over large spatial areas, InSAR has the potential to produce continental-scale maps of strain accumulation on active faults. However, most InSAR studies to date have focused on areas where the coherence is relatively good (e.g. California, Tibet and Turkey) and most analysis techniques (stacking, small baseline subset algorithm, permanent scatterers, etc.) only include information from pixels which are coherent throughout the time-span of the study. In some areas, such as Alaska, where the deformation rate is small and coherence very variable, it is necessary to include information from pixels which are coherent in some but not all interferograms. We use a three-stage iterative algorithm based on distributed scatterer interferometry. We validate our method using synthetic data created using realistic parameters from a test site on the Denali Fault, Alaska, and present a preliminary result of  10.5 ± 5.0  mm yr−1 for the slip rate on the Denali Fault based on a single track of radar data from ERS1/2.  相似文献   
994.
The Jinbaoshan ultramafic intrusion is a sheet-like body with a thick wehrlite unit in the center and thin pyroxenite units at the margins. PGE are enriched in several disseminated sulfide zones in the intrusion. Olivine from the intrusion has low Fo and depleted Ni contents compared to olivine from coeval Emeishan picrites. Whole rock major and trace element concentrations suggest that the Jinbaoshan wehrlites originally contained <30% trapped liquid. The total amount of sulfide in the rocks exceeds that which could have been dissolved in the trapped liquid. The Jinbaoshan wehrlites are interpreted to represent residual assemblages formed by dissolution of plagioclase by passing magma. No clear evidence of crustal contamination is indicated by S, Nd and Os isotopes. We envision that sulfide saturation occurred at depth due to olivine and chromite crystallization. Immiscible sulfide droplets were transported to the Jinbaoshan conduit where they accumulated and reacted with magma successively passing through the conduit to achieve high PGE concentrations.  相似文献   
995.
Using the model data for surface mass changes of the atmosphere, ocean, soil moisture and snow depth, the vertical crustal displacements of 25 ficual stations in China were calculated according to the ...  相似文献   
996.
利用热带降雨测量卫星(TRMM)的微波成像仪(TMI)和星载测雨雷达(PR)资料,从台风Acre(2004)接近台湾岛的观测资料中选取3个时次的数据,采用4种不同方法进行TMI反演降水试验。结果表明,常用的仅用高频通道反演降水方法的效果并不理想,多通道直接组合法的反演结果虽然稳定性很好,但始终无法达到最佳,多通道直接对数组合法的反演结果虽然有时较好,但反演结果不稳定,而多通道间接对数组合法既可以较好地表征弱降水区的范围和强度分布,又能描绘强降水区的位置,且反演效果稳定,是由微波亮温资料反演洋面降水的一种较为理想的方法。结果对于利用我国自行发射的气象卫星遥感资料反演降水具有一定的参考价值。  相似文献   
997.
Starting with the research status of bio-metallogenesis of TI deposits and their geology, this work deals with the geological background of TI enrichment and mineralization and the mechanism of bio-metallogenesis of TI deposits, as exemplified by TI deposits in the low-temperature minerogenetic province. This research on the bio-metallogenesis of TI deposits is focused on the correlations between bio-enrichment and TI, the enrichment of TI in micro-paleo-animals in rocks and ores, bio-fossil casts in TI-rich ores, the involvement of bio-sulfur in minerogenesis and the enrichment of bio-genetic organic carbon in TI ores. Thallium deposits have experienced two ore-forming stages: syngenetic bio-enrichment and epigenetic hydrothermal reworking (or transformation). Owing to the intense epigenetic hydrothermal reworking, almost no bio-residues remain in syngenetically bio-enriched TI ores, thereby the TI deposits display the characteristics of hydrothermally reoworked deposits. Supported by the National Natural Science Foundation of China (Grant No. 40372047)  相似文献   
998.
简要地介绍了斑点全息术的原理,分析了存在于实际数据中的各种噪声对功率谱造成的严重影响,讨论了消除噪声偏差的方法,最后报导了用斑点全息术对两双星的高分辨率象复原结果。  相似文献   
999.
西藏地震台网检测能力与定位能力评估   总被引:4,自引:3,他引:1  
根据西藏自治区地震台网的记录,对现有台站的检测能力和定位能力进行了评估,再把“十五”计划增加的台站加入西藏地震台网,估算了该区新台网的检测能力和定位能力。  相似文献   
1000.
The SHRIMP U-Pb ages of detrital zircon from the oldest Mesozoic strata, the Fanghushan Fomation, in the Hefei Basin range from 200 Ma to ca. 2500 Ma, which indicates that the Dabie Orogen as the early Jurassic sedimentary provenance was complex. The composition of the Dabie Orogen includes: the Triassic high pressure-ultrahigh pressure metamorphic rocks, of which the detrital zircon ages are from 234 Ma to 200 Ma; the rocks possibly related to the Qinling and Erlangping Groups representing the southern margin of the Sino-Korean craton in the Qinling and Dabie area, of which the detrital zircon has an age of 481-378 Ma; the Neo-proterozoic rocks originated from the Yangtze croton, of which the detrital zircon ages are 799-721 Ma old; and the rocks with the detrital zircon ages of ca. 2000 Ma and ca. 2500 Ma, which could be the old basement of the Yangtze craton.  相似文献   
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