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141.
142.
Automatic phase picking is a critical procedure for seismic data processing, especially for a huge amount of seismic data recorded by a large-scale portable seismic array. In this study is presented a new method used for automatic accurate onset phase picking based on the proporty of dense seismic array observations. In our method, the Akaike's information criterion (AIC) for the single channel observation and the least-squares cross-correlation for the multi-channel observation are combined together. The tests by the seismic array observation data after triggering with the short-term average/long-term average (STA/LTA) technique show that the phase picking error is less than 0.3 s for local events by using the single channel AIC algorithm. In terms of multi-channel least-squares cross-correlation technique, the clear teleseismic P onset can be detected reliably. Even for the teleseismic records with high noise level, our algorithm is also able to effectually avoid manual misdetections. 相似文献
143.
地震资料解释是地震勘探的核心环节,但地震资料解释人员一些认识上误区在一定程度上制约了着它的发展。通过实例,介绍了当前的资料解释人员存在的七种主要误区,并分别对这些认识误区进行了深入的分析,探讨其错误实质及危害,以帮助资料解释人员树立一种地震资料解释的科学思维,提高地震资料解释水平。 相似文献
144.
Climatic change during the last 4000 years in the southern Tarim Basin,Xinjiang, northwest China 总被引:1,自引:0,他引:1
In this study, a ca. 4000 cal. yr ancient lacustrine (or wetland) sediment record at the southern margin of Tarim Basin is used to reconstruct the history of climate change. Six radiocarbon dates on organic matter were obtained. δ18O and δ13C of carbonate, pollen and sediment particle size were analysed for climate proxies. The proxies indicate that a drier climate prevailed in the area before ca. 1010 BC and during period 1010 BC–AD 500 climate then changed rapidly and continuously from dry to moist, but after about AD 500 climate generally shows dry condition. Several centennial‐scale climatic events were revealed, with the wettest spell during AD 450–550, and a relatively wetter interval between AD 930–1030. Pollen results show that regional climate may influence human agricultural activities. Spectral analysis of mean grain size (MGS) proxy reveals statistically pronounced cyclic signals, such as ca. 200 yr, ca. 120 yr, ca. 90 yr, ca. 45 yr and ca. 33 or 30 yr, which may be associated with solar activities, implying that solar variability plays an important role in the decadal‐ and centennial‐scale climate variations in the study area. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
145.
针对在卵石及基岩地层中桩孔施工时成孔难、渗漏大的问题,以液压抓斗为成孔设备,采用合理的机械结构、钻进方法、泥浆配方进行矩形截面桩的施工。 相似文献
146.
湖南洞庭湖地区土壤中Hg的来源 总被引:1,自引:0,他引:1
Hg污染已成为全球性的环境问题,尤其是Hg对土壤的污染,因其具有隐蔽性、不可逆性和长期性的特点,对陆生生态系统构成潜在的巨大威胁,因此查明土壤中Hg的来源非常重要。运用生态地球化学填图的指导思想,对湖南洞庭湖地区土壤剖面分析和成土过程研究后发现,表层土壤中Hg含量的高低与成土母质中Hg的含量有很好的对应性,成土过程对土壤中Hg的含量也有显著的影响。 相似文献
147.
北祁连西段作为甘肃一个重要的多金属成矿带,随着地质找矿工作不断地加强,日渐重要。根据熬油沟及卡洼沟一带水系沉积物、岩屑和岩石剖面测量结果,对Au、Pt、Pd和Pb、Zn等成矿元素的分布特征和组合关系进行了分析,总结了该处成矿地质背景和地球化学异常特征,指出了找矿方向。 相似文献
148.
Instability characteristics of the East Asian Monsoon recorded by high-resolution loess sections from the last interglacial (MIS5) 总被引:3,自引:0,他引:3
Guan QingYu Pan BaoTian Gao HongShan Li BingYuan Wang JunPing Su Huai 《中国科学D辑(英文版)》2007,50(7):1067-1075
The selection of high-resolution loess sections is needed in order to determine the climatic variability of the East Asian Monsoon during the last interglacial. Two sequences of S1 on the eastern and west-ern sides of the Liupan Mountain were both composed of five paleosol layers and four loess layers,indicating that there were five strong summer monsoon events and four strong winter monsoon events in MIS5. This corresponds with other records of the East Asian Monsoon,along with NGRIP and the North Atlantic records,implying that the climate of the Northern Hemisphere was very instable during the last interglacial. Two layers of paleosols and one layer of loess had developed during MIS5a and MIS5c. Compared with MIS5e,the climate in MIS5a and MIS5c fluctuated more intensively on a millen-nial scale,whereas the climate was relatively stable in MIS5e. 相似文献
149.
150.
云驾岭矿区上部黄土中夹杂大量卵砾石,下部地层则因岩浆岩侵入具有岩硬、破碎、漏水、掉块等特性,严重影响钻进效率。为克服卵砾石及硬岩钻进难题,选用多工艺液压钻机YHJ-2000及性能参数比较稳定1150-XH空压机等钻探设备。采用牙轮钻头钻进、气动潜孔锤以及金刚石复合片等复合钻进工艺,并根据地层岩性确定钻孔结构、钻具组合及钻进参数。施工中注意调整泥浆性能,保证泥浆携带岩粉能力。经实践验证,该区采用的钻进工艺和方法,有效地提高了钻效,达到500m/月。 相似文献