重复绝对重力测量观测的滇西地区和拉萨点的重力变化及其意义

根据近年来在滇西地区和西藏拉萨绝对重力点上的一些新的绝对重力重复观测结果 ,对1990年以来在这些点上绝对重力重复观测结果进行了分析. 滇西地区的5个绝对重力观测 点的近10年的重复观测结果表明,大部分观测时段没有出现与地球动力学事件有关的重力变 化,只有丽江和洱源2个绝对重力观测点的观测结果显示丽江地震前后有变化. 为了研究该 重力变化的原因,本文正演模拟了出现重力变化期间丽江地震同震位错引起的重力变化,模 拟结果与实际观测结果有较好的一致性. 西藏拉萨近10年以来的重复观测结果给出了拉萨点 的绝对重力值以-1.82±0.9×10-8m·s-2·a-1速率下降,这从重力学 的角度反映出青藏高原的隆升. 对拉萨点的重力变化机制进行了探讨,根据印度板块与欧亚 大陆俯冲模型计算的拉萨点重力变化速率与观测到的重力变化速率较一致,表明现今拉萨地 区重力变化是由于印度板块与欧亚大陆俯冲所引起. 根据印度板块向欧亚大陆俯冲的位错模 型计算的拉萨点的重力变化与地表垂直位移的关系,将重力变化转换为拉萨点的隆升速率为 8.7mm/a.      

京都大学重力基准点(京都C)的绝对重力变化

京都大学大学院理学研究科地球物理学教室重力基准点 (京都C)自被确认为国际重力基准网 1 971 (简称IGSN 71 )的重力基准点以来 ,已进行过许多次重力测量 ,尤其是作为相对重力测量的基准点而发挥了巨大的作用。不仅如此 ,京都C还被列为国际绝对重力基准网的B重力点而成为监测地形变地区重力变化的重要基准点。近年 ,由于简便的移动式绝对重力仪的普及 ,日本国内的一些单位可以到各地开展重力测量。例如 ,国土地理院和国立天文台水泽站就到京都C进行过绝对重力测量。京都大学大学院理学研究科 1 999年 3月购入了高分辨率绝对重力仪FG 5,…     

1996-2003年中国大陆高精度绝对重力观测

近十年间利用自由落体式绝对重力仪(FG5/112)对分布在全国55个测点进行了绝对重力测定,观测精度均优于5×10-8 ms-2,对其中80%以上的测点还作了重复观测,文中给出了观测精度及其测量结果的互差.上述的测量极大地改善了我国目前重力网的精度和覆盖率,并为研究重力场的变化提供了重要的基础资料.本文还对观测结果和存在问题作了初步分析并提出有关建议.     

1996年中国中西部地区高精度绝对重力观测结果

1996年,中国科学院测量与地球物理研究所利用目前国际上最先进的FGS／112型绝对重力仪,在我国中西部地区的湖北、四川、云南和广西省开展绝对重力测量．给出了15个绝对重力点的最新观测结果,并与其他类型仪器在一些点上的观测结果进行了比较．结果表明,FGS／112绝对重力仪在15个点的观测结果的精度优于2．78×10－8m／s2．该仪器具有较好的稳定性和重复性,并与其他类型仪器没有明显的系统误差．     

庐山重力基线场稳定性分析

利用2018年庐山重力短基线场绝对重力和相对重力观测资料,基于绝对重力控制下的相对重力联测方式对庐山基线场的稳定性进行了分析。结果表明：庐山基线场2015～2018年测段重力变化为-11.6～13.4μGal、均值-0.962μGal,较小的重力变化表明庐山短基线重力场较稳定;2000～2018年测段重力变化为-39～33.5μGal、均值-0.275μGal,总体以G16测点为界呈分化特征,上山侧（G16～JZ04）重力变化较平缓（约-3 μGal）,下山侧（G03～G16）因G04、G14测点重力值变化显著（分别为-24.95、-18.5μGal）,导致相邻测段重力变化剧烈;测段重力变化与段差比值（B）为1.19×10^-4～3.58×10^-3;庐山及其周边地区由地表垂直运动引起的重力变化速率为0.7543±0.16μGal/a;近期研究区地震活动性呈震级小、沿断裂带集中分布特征;重力变化对相对重力仪一次项系数标定结果影响较大（正比于B值）,对校正精度影响小,利用以往重力观测成果进行一次项系数标定时,绝对重力测段JZ02～JZ04误差影响小于最大重力段差测段,定期维护和复测是保障高精度重力短基线场的有效途径。     

我国绝对重力观测结果和重力测量精度

文内给出全国３６个点绝对重力观测结果。观测结果表明，在国家重力基本网的一些点上，其重力值新测绝对重力值之间存在明显偏差。     

安庆5.2级地震震前区域重力场动态变化特征

根据安徽省及周边区域地震动态重力监测网2009-2010年期间的3期绝对重力和相对重力观测成果,给出了监测区域重力场动态变化图像,并以此为基础从场变化的角度分析了安庆地震震前区域重力场的动态变化特征.     

绝对重力测量在云南和北京观测到的重力时间变化

中国地震局地震研究所与德国汉诺威大学大地测量研究所于１９９０,１９９２和１９９５年共同在滇西地震预报实验场和昆明进行了３次绝对重力测量。此外,１９９０,１９９２年在北京,１９９０年在武汉也进行了绝对重力测量。通过对各次绝对测量的结果进行比较,并与其它重力仪获得的数据的对比估算了它们的可靠性,进而详细地讨论了各个测点的重力变化。     

面向绝对重力测量的振动补偿技术发展

绝对重力仪是用于直接测量重力加速度值的精密仪器,可以作为计量标准器对相对重力仪进行定期校准.现有绝对重力仪的测量精度可达微伽(1μGal=1×10-8m/s2)量级,测量精度主要受振动噪声的限制.垂直隔振和振动补偿技术是目前常用的两种处理振动噪声的方法.随着绝对重力仪在野外流动重力观测和海洋/航空重力测量中的应用需求日...     

首次观测到的由地震引起的绝对重力变化

首次用绝对重力测量观测到明确的同震重力变化。恰好在1次M6．1地震的前1天和震后7天进行了绝对重力测量。观测到的绝对重力变化为－6μGal,显著地大于约1μGal的观测误差。特别有意义的是，所观测到的空间重力变化与仅用位移数据建立起来的弹性位错模型预测的结果非常一致。该结果强烈地激励我们对重力和位移同时进行反演，以更好地了解地震。     

Absolute airborne gravimetry: a feasibility study

We report here the results obtained during a feasibility study that was pursued in order to evaluate the performances of absolute airborne gravimetry. In contrast to relative systems, which use spring‐type gravimeters, each measurement acquired by absolute systems is independent from the others and the instrument is not suffering from problems like instrumental drift, frequency response of the spring and variation of the calibration factor. After a validation of the dynamic performance of the experimental setup in a moving truck, a comparison between the experimental airborne data retrieved over the Swiss Alps and those obtained by ground upward continuation at flight altitude allow us to state that airborne absolute gravimetry is feasible. The first test flight shows a spatial resolution comparable to those obtained by relative airborne gravimetry. For a wavelength on the order of 12 km the absolute value of gravity can be evaluated with an uncertainty of 6.9 mGal.     

Plumb line deflection varied with time obtained by repeated gravimetry

IntroductionPlumb line deflection (PLD) express the incline between the geoid and the surface of ellipsoidal earth, i.e., the deflection of the real plumb line of calculating point to the normal direction of the corresponding point in the ellipsoidal surface. It varied in the range of about 3(~5( generally, and the largest value will be 20(~30( in spatial domain. Plumb line is closely related to spatial distribution of gravity field on the earth surface. PLV of a point on the earth surface c…     

陆地高精度重力观测数据的应用研究进展

陆地重力观测相较于航空和卫星重力观测,距离场源更近,观测精度相对较高,其静态异常和时变数据已广泛应用于研究多种地球动力学问题.21世纪以来,绝对重力观测技术发展迅速,陆地观测网络日益完善,高精度陆地重力观测数据产品逐渐丰富,基于这些产品的大地测量和地球物理研究不断取得新进展.本文总结了近十几年来高精度陆地重力观测数据在大地测量和地球物理领域的应用进展情况,包括基于重力异常数据构建重力场和大地水准面模型、建立地壳物性结构模型、反演Moho界面形态和估计岩石圈有效弹性厚度,以及利用时变重力数据构建时变重力场模型、探测微弱动力学信号、估计地壳构造变形速率和分析与火山、地震过程的可能关联,最后探讨分析了陆地重力测量的未来发展趋势,可为中国大陆重力观测系统建设与发展规划提供参考.     

Observing Gravity Change in the Fennoscandian Uplift Area with the Hanover Absolute Gravimeter

The Nordic countries Norway, Sweden, Finland and Denmark are a key study region for research of glacial isostasy. In addition, such research offers a unique opportunity for absolute gravimetry to show its capability as a geodetic tool for geophysical research. Within a multi-national cooperation, annual absolute gravity measurements have been performed in Fennoscandia by IfE since 2003. For the Hanover gravimeter FG5-220, overall accuracy of ±30?nm/s² is indicated for a single station determination. First results of linear gravity changes are derived for ten stations in the central and southern part of the uplift area. Comparing with the rates predicted by glacial rebound modelling, the gravity trends of the absolute measurements differ by 3.8?nm/s² per year (root-mean-square discrepancy) from the uplift model. The mean difference between observed and predicted rates is 0.8?nm/s² per year only. A proportionality factor of ?1.63?±?0.20?nm/s² per mm has been obtained, which describes the mean ratio between the observational gravity and height rates.     

地面扰动重力垂直梯度的确定

鉴于扰动重力垂直梯度在大地测量和物探中有重要作用,在未直接测量的情况下,对如何由地面重力异常及地形数据求取扰动垂直梯度进行了研究和分析,认为在被研点附近要求重力点分布密集,且精度不低于1×10-6ms-2;对中央区域积分奇异性问题也作了讨论;此外,扰动重力垂直梯度如何在大地测量和地球物理中进一步得到应用,以及为何用扰动重力垂直梯度代替重力异常垂直梯度也给予了简明的论述.     

绝对重力测量的进展及其研究动向

本文介绍了绝对重力仪和绝对重力测量的进展,提供了最近十几年来国际上绝对重力测量进行比对的结果。根据有关先进国家的研究计划,分析和讨论了绝对重力测量的发展趋势。     

Airborne Gradiometry Error Analysis

Gravity gradiometry is one of the older methods of determining the Earth’s local gravitational field, but lies in the shadow of more conventional static and moving-base gravimeter-based systems. While the static torsion balance appears to have been relegated to the museum, support for the airborne and space-borne differential accelerometer (gradiometer) continues so as to overcome limitations in spatial resolution and accuracy inherent in ordinary moving-base gravimetry. One airborne system exists, building on 30 year old technology concepts, and new technologies (e.g., cold-atom interferometry) promise significant improvements. Concomitant advances are required to measure accurately the angular velocity and angular acceleration of the platform, which inseparably combine (in an absolute sense) with the Earth’s gravitational gradients. A numerical analysis of instrument errors, with simulated aircraft dynamics, shows that navigation-grade gyros are just sufficient to account for these effects in gradiometers with 1E/ sensitivity. More accurate instruments, with 0.1 E/ sensitivity, require commensurate sensitivity in the gyros, of the order of 0.01°/h/ = 1.5\times10^{−4 °} \ for typical survey aircraft dynamics. On the other hand, typical orientation errors in the platform, which are problematic for vector gravimetry, are much less of a concern in gradiometry. They couple to the gradient signals and affect only the very low frequencies of the total gradient error.     

GRACE detection of the medium- to far-field coseismic gravity changes caused by the 2004 MW9.3 Sumatra-Andaman earthquake

Large earthquakes cause observable changes in the Earth's gravity field, which have been detected by the Gravity Recovery and Climate Experiment (GRACE). Since most previous studies focus on the detection of near-field gravity effects, this study provides the results from the medium- to far-field gravity changes caused by the 2004 Sumatra-Andaman earthquake that are recorded within GRACE monthly solutions. Utilizing a spherical-earth dislocation model we documented that large-scale signals predominate in the global field of the coseismic gravity changes caused by the earthquake. After removing the near-field effects, the coseismic gravity changes show a negative anomaly feature with an average magnitude of -0.18×10^-8 m·s^-2 in the region ranging ~40° from the epicenter, which is considered as the "medium field" in this study. From the GRACE data released by Center for Space Research from August 2002 to December 2008, we retrieved the large-scale gravity changes smoothed with 3 000 km Gaussian filter. The results show that the coseismic gravity changes detected by GRACE in the medium field have an average of (-0.20€±0.06)×10^-8 m·s^-2, which agrees with the model prediction. The detection confirms that GRACE is sensitive to large-scale medium-field coseismic gravitational effects of mega earthquakes, and also validates the spherical-earth dislocation model in the medium field from the perspective of satellite gravimetry.