关于垂线偏差时变

【作者】 李月锋；

【导师】 廖新浩； 李正心；

【作者基本信息】 中国科学院研究生院（上海天文台） ， 天文地球动力学， 2005， 硕士

【摘要】 物质运动和密度变化引起重力场随时间变化,地面一点的重力大小和方向会随之变化,这一点的垂线偏差也会发生相应的变化,这种变化就是垂线偏差的变化。一般人们把它划分为潮汐变化和非潮汐变化,本文涉及的是后者即非潮汐垂线偏差的变化(Non-tidal variations in the deflection of the vertical),简称为垂线偏差时变(Plumb line variation, PLV)。重力场变化量中所包含的关于地球内部物理状态的信息非常丰富,可以通过对垂线偏差的时变来加以研究,因而垂线偏差时变的研究对地球动力学的发展将发挥重要的作用。本论文介绍了垂线偏差时变的研究历史及其现状,尤其是近年来对EL Nino现象、地震等自然灾害的探讨和研究过程中发现和垂线偏差时变有关的现象。重点对其测定精度进行了研究和探讨。在已有的基础上对垂线偏差的计算公式进行了比较对照,确定了用重力位W时变微分公式进行计算思路清晰,形式简单,远区域的影响更小一些,计算精度不差于用扰动位T时变微分公式计算的精度,因此更加合理一些。测定垂线偏差时变的理论精度可达0.005″。结合华北重力网和云南重力网,进行了模拟计算,结果表明:在重力测量精度一定的条件下,测定垂线偏差时变的精度与重力点的分布有关,同一测网中各点的测定精度不一定相同,它取决于该点周围有限范围内(有效积分半径)重力点的密度和布设图形,特别是密度,更远一些点的情况对它的影响不是很大;在标准网中,如果重力布点的分辨率(相当于重力点的分布密度)达5′×5′以上,垂线偏差时变的测量精度平均值在0.0055″和0.0062″之间,可以达到理论精度值;在非标准网中,如果重力点的分辨率相当,用5′×5′的分辨率来网格化后,测量精度略低一些,如果重力点的分辨率较低,即便用5′×5′的分辨率来网格化后,测量精度也要低很多。虽然垂线偏差时变的提出已经很久了,但是以往对其研究并不很多,主要在于这方面的资料很有限,尽管我们的研究取得了一些结果,但同时也受到资料不足的影响。在本论文的最后部分针对这些问题进行了讨论,对未来的研究进行了展望,提出了进一步研究的方向。更多还原

【Abstract】 The movements of the material in the Earth arouses the redistribution of its density, which results in the variations of gravity field at a point with the time going. Meanwhile, the plumb-line deviation at the same point varies correspondly, which is called variation of the plumb-line deviation. It includes tidal variation and non-tidal variation. This paper involved only the latter, namely non-tidal variation in the deflection of the vertical, which is abbreviated for variation of plumb-line deflection(Plumb-line variation, PLV).There are much information about the physical state within the earth in the variation of gravity field, which can be studied through PLV. At the same time, studying PLV will play an important role in the development of geodynamics. In this dissertation, the history and current situation of the PLV’s researching are introduced, especially about the phenomena relevant to PLV during studying natural disasters such as EI Nino phenomena and earthquakes. This work emphasises on PLV’s precision. The formulae to calculate PLV are compared and it is shown that the formula on time-variation of gravity potential(W) is perfect. At present, the accuracy of time-variation of plumb-line deflection can be attained to 0″.005 and the influence from far area can be ignorable. A simulation on the characteristics of the data from the gravimetric network in North China and in West Yunnan is done. The conclusions are: 1.it can be verified that the precision of PLV averages between 0."0055 and 0."0062,with 0″.005 in the same order of magnitude. 2.it can be used 5′×5′gravity layouting in standard network. 3. it is reasonable to gridding in such resolution to calculate in non-standard network. 4. the accuracy of PLV in every point in the same network is determined directly by distribution of the points around it but has not much relation with the point amount in the whole network. Although there has been a long history of studying PLV, it is blindfold to some extent because it lacks related observation. We set some results in this research, but we also face the same problem that is short of earth observation. Finally, some prospection on further study are discussed.更多还原