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991.
海丰梅陇地区在1971、1981和1991年间曾先后发生3次小震群活动,前后两次小震群活动相隔10年。根据该地区的基岩、震源体、断裂规模以及新构造运动等特征,指出该区具有每隔一定时段便会出现周期性小震活动的规律,但发生大于5.5级破坏性地震的可能性很小。 相似文献
992.
993.
Jing-Cheng Han Guo-He Huang Hua Zhang Zhong Li Yong-Ping Li 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(4):973-989
Uncertainty analysis in hydrological modeling would help to better implement decision-making related to water resources management, which relies heavily on hydrologic simulations. However, an important concern will be raised over the uncertainty associated with watershed subdivision broadly applied in distributed/semi-distributed hydrological models since scale issues would significantly affect model performance, and thus, lead to dramatic variations in simulations. To fully understand the uncertainty associated with watershed subdivision level, however, is still a tough work confronting researchers because of complex modeling processes and high computation requirements. In this study, we analyzed this uncertainty within a formal Bayesian framework using a Markov Chain Monte Carlo method based on Metropolis–Hastings algorithm. In a case study using the semi-distributed land use-based runoff processes hydrologic model in the Xiangxi River watershed, results showed that the variation in the simulated discharges due to parameter uncertainty was much smaller than that due to parameter and model uncertainty under different watershed subdivision levels defined using aggregated simulation areas (ASAs). However, the posterior probability distribution of model parameters varied in response to subdivision levels, and four parameters (i.e. maximum infiltration rate, retention constant for slow store, maximum capacity for slow store, and retention constant for fast store) were identified with smaller uncertainty. Although the uncertainty in the simulated discharge due to parameter and model uncertainty varied little across subdivisions, the simulation uncertainty only due to parameter uncertainty was found to be reduced through increasing the subdivisions. In addition, the coarsest subdivision level (7 ASAs) was not sufficient for obtaining satisfying simulations in the Xiangxi River watershed, but inappreciable improvement was achieved through increasing the level among finer subdivisions. Moreover, it was demonstrated that increasing subdivision level would have no advantage of improving the reliability of hydrological simulations beyond the threshold (45 ASAs). The findings of this research may shed light on the design of operational hydrological forecasting in the Three Gorges Reservoir region with profound socio-economic implications. 相似文献
994.
Zhong He Jie Zhou ZhongPing Lai LinHai Yang JianMin Liang Hao Long XianJiao Ou 《Quaternary Geochronology》2010,5(2-3):102-106
The Mu Us Desert, located in the northwestern fringe of the East Asian monsoon region, is sensitive to climate variability. The desert is characterized by mobile, semi-fixed and fixed sand dunes. Alternating units of dune sands and sandy palaeosols in the Mu Us Desert imply multiple episodes of dune building and stabilization, in response to the ebb and flow of the East Asian monsoon. Desert evolution and climatic change of high-resolution in the Mu Us Desert are still poorly understood due to limited numerical dating results. In the present study, 19 samples collected from five sand dune sections along a northwest–southeast transect in the Mu Us Desert were dated using quartz optically stimulated luminescence (OSL) and single aliquot regenerative-dose (SAR) protocol. Internal checks of the OSL dating indicate that the SAR protocol is appropriate for equivalent dose (De) determination for the samples under study. Combined with the lithologic stratigraphy and the luminescence chronology, the sand dune development in the Mu Us Desert during the Late Pleistocene is discussed. Our results indicate that the sand was mobilized approximately at 91 ka, 71 ka, 48–22 ka, 5 ka, 1 ka, and 0.44 ka; the sand was fixed approximately at 65 ka and Holocene Optimum period in the interior Mu Us Desert. The Mu Us Desert formed at least before ~144 ka, and has shown increasing aridity in the Late Pleistocene. 相似文献
995.
996.
997.
Tieguan Wang Dujie Hou Ningning Zhong Jianping Bao Guanghui Huang Linye Zhang Zhilin Chen Peizhen Li 《中国科学D辑(英文版)》1997,40(1):54-64
Taking both eastern Linqing Depression and North Jiangsu Basin as examples, based on geochemical features of immature oils
as well as source inputs of hydrocarbons and macerals, it is revealed that a mixed source input of alga bio-lipids and higher
plant waxes is a basic characteristic of source material for immature oils in non-marine brackish-saline lacustrine basins.
Project supported by the “85–102” Chinese National Key Science and Technology Project and the National Gas Geochemistry Key
Laboratory, Lanzhou Institute of Geology, Chinese Academy of Sciences. 相似文献
998.
阐述包头数字地震遥测台网空间布局、子台台址的选取原则和台基地质条件,对选取的子台进行背景噪声测试,对拟建台网的地震监控能力和合理性进行评估,为包头数字地震遥测台网建设提供科学、经济的规划方案,以期对国内其他地区地震遥测台网建设、改扩建提供参考。 相似文献
999.
We use the slowness-azimuth station correction (SASC) method to improve the location accuracy of the Wenchuan aftershocks recorded by the Nagqu and Hotan seismic arrays. The results show that the standard deviations of back-azimuth and slowness errors of Wenchuan aftershocks recorded by the Nagqu array decreased by 32% and 58% respectively after correction. The decrease is 38 % and 71% for the Hotan array. After the correction, the location accuracy of all Wenchuan aftershocks recorded by the Nagqu array is improved. For the Hotan array, the accuracy is improved in the slowness estimation for 78 % of aftershocks and in back-azimuth estimation for all aftershocks. 相似文献
1000.
赣北及邻区休宁组(莲沱组)与湖北宜昌、通山地区的莲沱组是华南新元古代中期的重要地层单元,但对其沉积大地构造背景和时代归属一直存在不同认识。本文在详细的沉积学调查和区域对比研究基础上,对采自通山石门塘剖面莲沱组底部含砾砂岩、上部的沉凝灰岩和上饶华坛甘岭剖面的上墅组顶部英安岩、休宁组中部沉凝灰岩分别进行了LA-ICP-MS锆石U-Pb定年,获得通山莲沱组最大沉积年龄为784.0±11.0Ma,莲沱组中上部沉积年龄约为727.3±6.7Ma;获得华坛甘岭剖面上墅组顶部英安岩形成年龄为779.0±6.6Ma、休宁组中部沉积年龄为733.6±5.9Ma,因此,赣北及邻区的莲沱组或休宁组沉积时限与宜昌地区基本一致。沉积学调查显示,华坛甘岭休宁组沉积构造不发育,主体为冲积扇—滨浅海至深水陆棚相沉积;通山莲沱组沉积构造发育,斜层理、交错层理、沙纹层理及波痕等牵引流沉积构造发育,为河流—三角洲沉积序列。研究认为,在扬子陆块内,浙皖赣邻区的莲沱组(休宁组)与宜昌莲沱组、滇中澄江组及湘黔桂地区的板溪群及其相当地层的上部沉积时限(780~体相当,为南华冰期开启前在区域热沉降背景下,南华裂谷系的第一套呈区域性展布的裂谷盖沉积。 相似文献