重力数据库各项外部改正的计算

本文介绍的是在重力数据库系统中配备的一套重力各项外部改正计算的方法和程序,其中地形改正和均衡改正程序将远区改正范围划分为三个区:远一区为1或2公里至20公里,采用平面公式,高程数据网度为1公里×1公里;远二区为20公里至166.7公里,采用球面公式,高程数据网度为5′×5′;远三区为166.7公里至全球,采用球面公式旋转椭球体模型,为全球1°×1°高程数据网,各区一律用园域接口。为便于用户选择,每区备有多种方法。此外还备有高度改正,中间层改正和正常改正程序。用这个系统可以计算自由空间重力异常,布格重力异常和均衡重力异常值。     

纯球坐标系内各项重力校正值计算方案和计算过程

在国内,首次阐述了"纯球坐标系内各项重力校正值的计算方案和计算过程"。该计算方案有如下优点:①以观测点P为中心,以球面距离am=am-1+Δa.bm-1(m=2,3,…,M)为半径将计算区划分为M个环带,再以Δλ0为由P点出发射线的角度间隔将所有环带等分为N(整数)份的计算区划分方案是最严密拼接,因而校正值的计算精度相当高。②在地形复杂和相对高差大的情况下,通过减小Δa、b和Δλ0数值,可进一步提高计算精度。③可以直接采用带有经、纬度坐标的高程数据,进行大面积测区的各项重力校正值计算,而不受6°带和标准图幅限制。     

均衡重力异常计算方法

本文提出了采用埃利均衡补偿模式计算5ˊ×5ˊ平均均衡重力异常的一种方认。计算是使用5ˊ×5ˊ平均高程值,将A～O带分为近、中、远三个区:近区用1ˊ40〞×1ˊ40〞的柱体,中区用5ˊ×5ˊ的柱体,远区用15ˊ×15ˊ的柱体,分别采用矩形柱体、质线和质点的正演公式计算地形一均衡校正值。从华南某地区的均衡重力异常图可以看出,根据均衡重力异常可以消除由地壳厚度变化而产生的区域场,突出局部异常场。     

山区区域重力测量中间层校正系数的确定

山区区域重力测量中,地形校正范围的选择需要大一些,才能较好的消除地形起伏造成的影响,远区的地形和中间层影响均应考虑地壳弯曲的影响。因而在进行远区校正时,不能以过测点的平面为标准,而应以过测点的球面为标准,因此,地形校正值将会有负值出现。在进行中间层校正时,应消除与地形校正最大半径范围一致的弯曲圆盘的影响,此影响不仅与盘的半径有关,而且与厚度有关。本文给出对应于不同校正半径和不同厚度弯曲圆盘的一套理论计算结果,用这些结果得到的与不同校正半径配套的中间层校正公式,可供直接查阅使用。     

试论区域重力测量远区地改的精度

在区域重力资料整理中,拟从1:5万地形图上读取1×1公里的高程网,建立全国地形图网结点高程数据库,用于计算区域重力远区地形改正值。但在山区能达到多大精度？这里为大家提供一份典型山区地形改正的试验资料,并据此谈些粗浅的看法,供同志们参考。     

重力近区地形改正精度探讨

在大比例尺重力勘探工作中,近区、中区地形改正误差对重力总精度影响较大。在实际工作中,近区域地形改正一般采用实测或用地形图读图计算;中区地形改正一般采用地形图读图计算,《大比例尺重力勘查规范》只考虑地形图高程精度对重力总精度的影响,忽略了地形图平面坐标精度对重力总精度影响。这里从锥形、扇形基本地形改正公式推导出发,探讨不同比例尺,不同高程,平面精度对重力总精度的影响,并提出了不同地形改正精度对地形图比例尺及高程,平面精度要求建议。     

消息报导

吉林省地矿局物探大队自八十年代初以来,对吉林省及邻区的六十一万平方公里24739个数据的国家重力及航磁测量资料,采用相应的理论和方法,在M—160Ⅱ电子计算机上进行了计算处理。方法实验研究工作首先从确定计算莫霍面深度的区域重力异常开始,采用同一标准地壳厚度点,利用压缩质面法计算出相应的莫霍面深度,与已知地壳厚度进行拟合优度计算。最后选取了拟合优度较高、信息量又较丰富的60公里×60公里的富口圆滑布伽重力异常,並对松辽平原地区布伽重力异常选用无限大平板改正公式,进行了中新生代沉积层校正。以此做为计算莫霍面深度的区域重力资料。在地壳厚度与区域重力异常关系的研究中,利用东北三省的25个已知地震测深点数据控制地壳厚度,     

重力地改被积函数的一种快速算法

对于重力地形改正的计算,当积分公式与数字地形(即高程网)确定之后,其计算速度和精度主要取决于被积函数的处理方法。一、问题的提出众所周知,方域地形改正的计算公式为:     

北美国家高程基准面及重力异常计算方法的重大修改

北美以及加拿大、墨西哥和美国的重力数据库进行了两项重大修改:采用国际上接受的地球椭球面,而不是习惯使用的大地水准面或海平面作为重力测点的高程基准面;改进重力异常的计算方法。对北美国家现在使用的高度校正、布格校正、地形(海洋深度)校正、间接影响校正、曲率校正、大气校正,以及均衡补偿校正,均做了不同程度的修改。     

重力均衡与质量均衡

均衡理论，无论是艾礼模式，还是普拉特模式，都是建立在平面地壳的基础之上，并不考虑重力随高程的变化；这事实上相当于质量的均衡。如果在球面上考察均衡理论，并且考虑重力随高程的变化，则得到的均衡模型为重力的均衡。定量计算表明，质量均衡和重力均衡之间的差别是不可忽略的。这种差别对研究地壳的应力状态意义重大。     

Presolar grains from meteorites: Remnants from the early times of the solar system

This review provides an introduction to presolar grains - preserved stardust from the interstellar molecular cloud from which our solar system formed - found in primitive meteorites. We describe the search for the presolar components, the currently known presolar mineral populations, and the chemical and isotopic characteristics of the grains and dust-forming stars to identify the grains’ most probable stellar sources.     

Message from the Editor-in-Chief

正Dear Authors and Readers:First of all,on behalf of the new Editorial Board,I would like to express our sincere appreciation for your continuing support of our journal.This journal,founded in 1922,is the oldest geological journal in China.As the flagship journal of the Geological Society of China,it has become more and more influential in earth sciences in China and beyond.The journal is now indexed by SCI,CA and more than 20 other databases,with an impact     

Message from the Editor-in-Chief

正Dear Authors and Readers:First of all,on behalf of the new Editorial Board,I would like to express our sincere appreciation for your continuing support of our journal.This journal,founded in 1922,is the oldest geological journal in China.As the flagship journal of the Geological Society of China,it has become more and more influential in earth sciences in China and beyond.The journal is now indexed by SCI,CA and more than 20 other databases,with an impact     

Message from the Editor-in-Chief

Dear Authors and Readers：
First of all, on behalf of the new Editorial Board, I would like to express our sincere appreciation for your continuing support of our journal. This journal, founded in 1922, is the oldest geological journal in China. As the flagship journal of the Geological Society of China, it has become more and more influential in earth sciences in China and beyond. The journal is now indexed by SCI, CA and more than 20 other databases, with an impact factor varying between 1.58 and 2.15 from year to year. It is co-published by the Geological Society of China and Wiley-Blackwell Co.     

Message from the Editor-in-Chief

正Dear Authors and Readers:First of all,on behalf of the new Editorial Board,I would like to express our sincere appreciation for your continuing support of our journal.This journal,founded in 1922,is the oldest geological journal in China.As the flagship journal of the     

Beresellids from the Carboniferous of the Russian Platform

The classification of the tribe Bereselleae of the family Dasycladaceae is discussed in some detail. The genera Beresella, Samarella and Dvinella are placed in the tribe with Trinodella, being treated as a subgenus of Dvinella. A number of new species are described: four in Beresella, six in Dvinella subgenus Dvinella and two in Dvinella subgenus Trinodella. The stratigraphic occurrence of the tribe in the Carboniferous at a number of localities on the Russian Platform is represented and a strong generic-facies association is pointed out. A pattern of variation in morphological form with sediment type is also discussed. — W. Adey.     

Kinematic properties of the Galactic thick disk from data from the RAVE DR4 catalog

The analysis of the kinematic properties of the Galactic thick disk based on data from modern catalogs of stellar radial velocities and proper motions is presented. A new aspect of new determination of the kinematic characteristics of the thick disk is that the selected objects define this disk’s properties near the plane of symmetry. The velocity dispersion of stars in the Galactic thick disk in the radial direction and the direction of the Galactic rotation have been determined. The stellar-velocity distribution in the direction of the rotation is asymmetric. The parameters of this asymmetry have been determined, and the lag of the rotational velocity of the thick disk relative to objects in the thin disk estimated. The value of this “asymmetric drift,” about 20 km/s, suggests larger spatial scales for the kinematic characteristics in the radial direction for the Galactic thick disk than for the thin disk.