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791.
Seismic ground motion relationship in southern China based on stochastic finite-fault model 总被引:1,自引:0,他引:1
The characteristics of seismic ground motions in southern China are difficult to determine statistically due to a lack of strong ground motion data. In this study, a stochastic finite-fault ground motion model was adopted to simulate the seismic ground motions at bedrock for southern China, based on parameters derived from small and medium earthquakes that have occurred in the region. From these, the response spectra was estimated. A set of ground motion attenuation relations hipswas then developed based on simulated peak ground motions and response spectral parameters through regression, which would be applicable for use in engineering practice. Through comparisons, it was demonstrated that the proposed ground motion relationships are generally consistent with those obtained from other reported ground motion attenuation models for southern China. 相似文献
792.
Corundum-rich garnetite occurs as an isolated lens in a garnet peridotite body in the Donghai area of the Sulu ultrahigh-pressure (UHP) terrane. This rock consists of garnet and corundum, along with minor crack-related zoisite, pargasite, Mg-staurolite, Mg-chloritoid, sapphirine and chlorite. Pyropic garnet (Prp54–63Grs26–36Alm10–12) exhibits a sinusoidal REE pattern, positive Ta, Pb, and negative Nb, Ti anomalies due to metasomatism. Reddish corundum contains 1.1–1.7 wt% Cr2O3, and shows three oriented sets of exsolved rutile needles. Both garnet and corundum contain inclusions of apatite, Mg-allanite (MgO>4 wt%), and Ni-Fe sulfides formed as trapped Ni-Fe-S melt. The protolith of the corundum-rich garnetite could have been spinel websterite formed in the upper mantle. Both the websterite and the host garnet peridotite were subjected to subduction-zone UHP metamorphism at 800 °C and >4 GPa. Crack-related hydrous phases were formed by fluid infiltration during exhumation.Editorial responsibility: T.L. Grove 相似文献
793.
Jianping?Zheng W.?L.?GriffinEmail author Suzanne?Y.?O’Reilly Fengxiang?Lu Chunmei?Yu Ming?Zhang Huimin?Li 《Contributions to Mineralogy and Petrology》2004,148(1):79-103
Mafic xenoliths from the Paleozoic Fuxian kimberlites in the North China craton include garnet granulite, and minor pyroxene amphibolite, metagabbro, anorthosite and pyroxenite. The formation conditions of the amphibolites are estimated at 745–820 °C and 7.6–8.8 Kb (25–30 km); the granulites probably are derived from greater depths in the lower crust. LAM-ICPMS U–Pb dating of zircons from four granulites reveals multiple age populations, recording episodes of magmatic intrusion and metamorphic recrystallisation. Concordant ages and upper intercept ages, interpreted as minimum estimates for the time of magmatic crystallisation, range from 2,620 to 2,430 Ma in three granulites, two amphibolites and two metagabbros. Lower intercept ages, represented by near-concordant zircons, are interpreted as reflecting metamorphic recrystallisation, and range from 1,927 to 1,852 Ma. One granulite contains two metamorphic zircon populations, dated at 1,927±55 Ma and 600–700 Ma. Separated minerals from one granulite and one amphibolite yield Sm–Nd isochron ages of 1,619±48 Ma (143Nd/144Nd)i=0.51078), and 1,716±120 Ma (143Nd/144Nd)i=0.51006), respectively. These ages are interpreted as recording cooling following metamorphic resetting; model ages for both samples are in the range 2.40–2.66 Ga. LAM-MC-ICPMS analyses of zircon show a range in 176Hf/177Hf from 0.28116 to 0.28214, corresponding to a range of Hf from –34 to +12. The relationships between 207Pb/206Pb age and Hf show that: (1) the granulites, amphibolites and metagabbro were derived from a depleted mantle source at 2.6–2.75 Ga; (2) zircons in most samples underwent recrystallisation and Pb loss for 100–200 Ma after magmatic crystallisation, consistent with a residence in the lower crust; (3) metamorphic zircons in several samples represent new zircon growth, incorporating Hf liberated from breakdown of silicates with high Lu/Hf; (4) in other samples metamorphic and magmatic zircons have identical 176Hf/177Hf, and the younger ages reflect complete resetting of U–Pb systems in older zircons. The Fuxian mafic xenoliths are interpreted as the products of basaltic underplating, derived from a depleted mantle source in Neoarchean time, an important period of continental growth in the North China craton. Paleoproterozoic metamorphic ages indicate an important tectonic thermal event in the lower crust at 1.8–1.9 Ga, corresponding to the timing of collision between the Eastern and Western Blocks that led to the final assembly of the North China craton. The growth of metamorphic zircon at 600–700 Ma may record an asthenospheric upwelling in Neoproterozoic time, related to uplift and a regional disconformity in the North China craton. 相似文献
794.
Preliminary study on PAH degradation by bacteria from contaminated sediments in Xiamen Western Sea,Fujian, China 总被引:1,自引:0,他引:1
In order to estimate the biodegradation of three polycyclic aromatic hydrocarbons (PAHs) compounds, bacterial strains were isolated from marine sediments in three heavily contaminated sites (Yuandang Lake, Dongdu Port and Aquacultural zones in Maluan Bay) in Xiamen Western Sea. The results show three bacterial strains, which used pyrene as the sole carbon source, were identified as strains of Aureobacterium sp.,Arthrobacter sp., Rhodococcus sp. The PAH-degrading bacteria isolated had a strong ability to degrade phenanhrene, fluoranthene and pyrene at different degradation rates. The highest degradation rate was observed when three PAH compounds were mixed with an individual strain in the medium. The three PAHs were degraded after one week with a degradation rate of 89.94 % for phenanthrene and 93.4 % for both of fluoranthene and pyrene.In addition, after 25 days of incubation, the degradation rate was 99.98 % for phenanthrene and 99.97 % for both of fluoranthene and pyrene. Optical density was measured to estimate bacterial growth during the degradation of PAHs. Highest levels of bacterial growth were observed with a three PAH mixture in the culture, suggesting that the concentration of PAHs influenced bacterial growth and the highest levels of degradation for most series were detected after one week of incubation. 相似文献
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798.
利用HJ-1A/1B卫星CCD数据进行黄河凌汛监测,提出了基于主成分分析和决策树的冰凌提取方法。实验结果显示,利用HJ-1A/1B卫星CCD数据能有效地提取出黄河的冰凌范围,对黄河凌汛监测具有较大的应用潜力。 相似文献
799.
GPS信噪比观测值的土壤湿度变化趋势反演 总被引:1,自引:0,他引:1
土壤湿度变化趋势是某一个位置或区域内水资源循环的重要指标.多路径误差作为一种在导航、定位中的重要测量误差,由于其较弱的空间相关性,难以采用全球甚至区域性模型或差分的方法予以消除.在讨论和研究了多路径误差反射模型的基础上,实现了利用 GPS信噪比 SNR(Signal - to - NoiseRatio)观测值中的多路径反射分量对土壤湿度变化趋势的模拟.结合实测 GPS数据和土壤湿度计观测数据的对比和分析表明,该方法能反映土壤湿度变化趋势.同时,在计算过程中如何选择合适卫星、对反演结果质量进行评价以及如何实现两种观测结果之间的同化等是进一步需要研究的问题. 相似文献
800.
乌镇旅游发展模式解析 总被引:2,自引:0,他引:2
我国古镇旅游在快速发展的同时也在开发和经营中遇到了诸多问题,乌镇二期则走出了一条创新发展的路径,实现了古镇旅游的提升和转型.在分析古镇旅游发展模式的基础上,从产权、产品、经营和社区参与度4个维度上系统地解析了乌镇旅游发展模式,并针对目前古镇旅游发展中所产生的问题提出了今后的发展方向和建议,为其他古镇的合理开发、发展模式创新和可持续发展提供借鉴. 相似文献