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51.
震后趋势早期判断的初步研究 总被引:7,自引:1,他引:7
本文系统清理了云南及邻近地区1965年以来106个地震序列,对h、b、K、U、等值的震后趋势早期(7天以内)判断指标和预报能力;双震型序列中h、b值的联合早期判断;前震、多震型序列的地震波特征等方面进行了初步研究,并将权重集成法应用于地震序列的早期综合判断中,提取了各单项方法的权重系数和权重集成值的临界阈值。 相似文献
52.
中纬度地区混合云中稳定同位素分馏的数学模拟—以乌鲁木齐降水为例(英) 总被引:10,自引:0,他引:10
介绍的数学模型考虑了混合云中液、固态共存时以及冰面过饱和环境下稳定同位素的动力分馏效应。利用该数学模型,模拟了不同冷却条件下稳定同位素的温度效应。在相同的湿度条件下,湿绝热冷却过程中δ18O随温度的变化率小于等压冷却过程。冰面过饱和比Si的增大意味着动力分馏效应的增大。与平衡态相比,它的作用使得稳定同位素的综合分馏系数减小,从而使得降水中δ18O随温度的变化趋缓。模拟显示,湿绝热冷却过程中大气水线(MWL:=bδ18o+d)的斜率b和常数d均大于等压冷却过程。全球大气水线位于湿绝热冷却过程和等压冷却过程条件下分别模拟的两条大气水线之间。b和d的大小与Si呈正比。Si愈大,动力分馏效应愈强,b和d也愈大。反之亦然。然而,b和d的大小对云中含水量的变化具有低的敏感性。利用动力分馏模式模拟了乌鲁木齐降水中稳定同位素的变化。模拟的稳定同位素比率-温度以及δD-δ18O曲线分别与乌鲁木齐实测的稳定同位素比率-温度同归线以及大气水线有非常好的一致性。 相似文献
53.
Discovery of the Middle-Late Triassic elasmobranch ichthyoliths from the Guanling area,Guizhou,SW China 总被引:4,自引:0,他引:4
应用Johns等(1997)的形态分类系统,对首次报道出现于贵州关岭地区中上三叠统的软骨鱼类的微体化石进行了初步研究,描述了其中的1个牙齿化石(可能属于弓鲛鳖科的)和7个鳞片类化石的形态属种,其中包括两个鳞片类化石的新属种,即Lobaticorona cf. floriditurris,Sacrisubcorona co. circabasis,Glabrisubcarona co.arduidevexa,Parvi-corona dacrysulca n.gen.et.n.sp.s.f.Annulicorona pyramidalis n.gen.et.n.sp.s.f.,new(?) paragenera A和new(?) paragenera B。还初步探讨了软骨鱼类微体化石在三叠纪地层划分中的应用,以及中国西南部三叠纪软骨鱼类与北美相当地层中软骨鱼类的洲际对比。 相似文献
54.
贵州关岭生物群的埋藏环境与古生态特点 总被引:8,自引:1,他引:8
新建并逐层描述了含关岭生物群的上三叠统小凹组。根据小凹组下段岩石学、地球化学和生物群生态特征分析,指出关岭新铺乡一带在晚三叠世时为一个三面环陆、一面可能与特提斯大洋相通的局限海湾。关岭生物群中少量完好保存的植物化石的生态特点指示该区当时具有热带、亚热带的气候特点,雨水充沛。元素地球化学特征则显示海湾中的海水可能受间歇性大量淡水注入影响而出现间歇性淡化,并导致生物原来赖以生存的海洋环境出现间歇性缺氧,而发生生物集群死亡和埋藏。 相似文献
55.
The humidity effect, namely the markedly positive correlation between the stable isotopic ratio in precipitation and the dew-point deficit △Td in the atmosphere, is put forward firstly and the relationships between the δ18O in precipitation and △Td are analyzed for the Urumqi and Kunming stations, which have completely different climatic characteristics. Although the seasonal variations in δ18O and △Td exhibit differences between the two stations, their humidity effect is notable. The correlation coefficient and its confidence level of the humidity effect are higher than those of the amount effect at Kunming, showing the marked influence of the humidity conditions in the atmosphere on stable isotopes in precipitation.Using a kinetic model for stable isotopic fractionation, and according to the seasonal distribution of meanmonthly temperature at 500 hPa at Kunming, the variations of the δ18O in condensate in cloud aresimulated. A very good agreement between the seasonal variations of the simulated mean δ18O and themean monthly temperature at 500 hPa is obtained, showing that the oxygen stable isotope in condensateof cloud experiences a temperature effect. Such a result is markedly different from the amount effect atthe ground. Based on the simulations of seasonal variations of δ18O in falling raindrops, it can be foundthat, in the dry season from November to April, the increasing trend with falling distance of δ18O in fallingraindrops corresponds remarkably to the great ATd, showing a strong evaporation enrichment function infalling raindrops; however, in the wet season from May to October, the δ18O in falling raindrops displaysan unapparent increase corresponding to the small ATd, except in May. By comparing the simulated meanδ18O at the ground with the actual monthly δ18O in precipitation, we see distinctly that the two monthlyδ18O variations agree very well. On average, the δ18O values are relatively lower because of the highlymoist air, heavy rainfall, small △Td and weak evaporation enrichment function of stable isotopes in thefalling raindrops, under the influence of vapor from the oceans; but they are relatively higher because of the dry air, light rainfall, great △Td and strong evaporation enrichment function in falling raindrops, under the control of the continental air mass. Therefore, the δ18O in precipitation at Kunming can be used to indicate the humidity situation in the atmosphere to a certain degree, and thus indicate the intensity of the precipitation and the strength of the monsoon indirectly. The humidity effect changes not only the magnitude of the stable isotopic ratio in precipitation but also its seasonal distribution due to its influence on the strength of the evaporation enrichment of stable isotopes in falling raindrops and the direction of the net mass transfer of stable isotopes between the atmosphere and the raindrops. Consequently, it is inferred that the humidity effect is probably one of the foremost causes generating the amount effect. 相似文献
56.
水体蒸发过程中稳定同位素的分形机制 总被引:1,自引:0,他引:1
The variations of stable isotopes in atm ospheric vapor and precipitation are caused by stableisotopic fractionation during phase changes in w ater cycle. The isotopic fractionation m ainlyhappens in the m ass transportation of stable isotopes from free w… 相似文献
57.
论述了孟连7.3级地震的中、短、临三个阶段较成功预报的过程及所取得的减灾效益,同时较详细介绍了地球整体观的预报思路,提出孕震系统是一个开放的复杂巨系统,应将源、场及地球环境视为一个整体,各子系统内部和它们之间存在非线性的相互约束和反馈的观点。在预报研究进展方面阐述了建立多维预报指标、预报新方法的应用,孕震系统宏观层次上的单元体应力水平群体涨落模型等有关内容 相似文献
58.
59.
降水中稳定同位素作为水中的组成成分,与水汽来源的变化存在直接的关系。根据在青藏高原降水中稳定同位素的研究,青藏高原南北降水中δ18 O和过量氘(d)都存在着显著的空间变化,这种空间变化与西南季风夏季向北推进的位置有关。在时间变化上,青藏高原不同地区降水中δ18 O和d的季节变化特征也与水汽来源的季节变化有关,而且这种季节变化主要受控于西南季风水汽与西风带输送水汽之间的相互作用,在中国最北端的阿尔泰山区还受到极地气团的影响。由于不同的大气环流造成的水汽来源的差异,青藏高原冰芯中稳定同位素变化也存在空间差异。北部地区冰芯中稳定同位素的年际变化与当地气象站记录显示良好的对应关系,而南部冰芯中稳定同位素的变化与当地气象站降水量在年际变化上显示反相关关系。 相似文献
60.
Expeditions to Muztagata (in the eastern Pamirs) during the summer seasons of 2002 and 2003 collected precipitation samples and measured their oxygen isotopes. The δ18O in precipitation displays a wide range, varying from -17.40‰ to +1.33‰ in June-September 2002 and from -22.31‰ to +4.59‰ in May-August 2003. The δ18O in precipitation correlates with the initial temperature of precipitation during the observing periods. The positive correlation between δ18O and tem- perature suggests that δ18O can be used as an indicator of temperature in this region. The δ18O values in fresh-snow samples collected from two snow events at different elevations on the Muztagata Glacier show a strong "altitude effect", with a ratio of nearly -0.40‰ per 100 m from 5500 m to 7450 m. 相似文献