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基于标准大气定律和大气圆柱体分布模型,本文引进了大气重力格林函数,用离散格积方法求得了大气对重力场观测的影响,对台站高程、周围地形和地表温度变化等因素的影响问题进行了讨论．结果说明台站近区气压变化是大气重力信号的主要贡献者,考虑大气质量负荷引起的弹性地球形变效应后,对距台站0．5°的区域积分获得的大气重力导纳值为-0．3603μGal／hPa,占全球大气变化引起的总信号的90％以上,这一理论模型结果与超导重力仪实测结果相吻合,并能较有效地用于消除重力观测中的气压干扰成分． 相似文献
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This paper reviews how the study of the surface gravity changes is able to provide useful information on the Earth's structure and global dynamics. The spectral range which is observable with superconducting gravimeters is broad and goes from the seismic frequency band to periods longer than one year. We first investigate the seismic and sub-seismic bands with a special attention paid to the gravity detection of core modes in the liquid core and to the Slichter mode of translation of the solid inner core. In the tidal bands, we show how accurate measurements allow us to infer constraints on various phenomena such as mantle (an-)elasticity, as well as ocean and atmospheric loading. The observation of the Free Core Nutation resonance in the diurnal frequency band is reviewed and indirectly suggests an increase in the ellipticity of the core-mantle boundary with respect to its hydrostatic value. A similar resonance is also theoretically predicted in the diurnal band for the rotation of the solid inner core (Free Inner Core Nutation) but we show that its detection is much more difficult because of the small amplitude and lack of a nearby tidal frequency. Oceanic and atmospheric loading mechanisms induce gravity changes over a wide spectral range and we present some recent progress in this field. Finally, because superconducting gravimeters have high calibration stability and small long-term instrumental drift, they can easily measure longperiod gravity variations due to polar motion and hydrogeology. 相似文献
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Among the 21 superconducting gravimeters presently operating worldwide four instruments exist that are equipped with two vertically aligned sensor units. Three of the instruments are installed in Germany (Bad Homburg, Moxa, Wettzell) and one in South Africa (Sutherland). Comparisons of the data sets obtained with the dual sensor systems yield information on instrumental effects and sensitivity as well as on the efficiency of reductions of environmental effects applied to the data. The latter is an important constraint when looking for small geodynamic signals like Slichter and core modes or aperiodic variations.From analyses of the two data sets of each instrument a small but significant difference of 1-3% in the response of the sensor units on barometric pressure variations is found. Likewise, the records of lower and upper sensor vary slightly but not systematically with regard to the noise levels in the different frequency ranges. The tidal analyses yield an agreement of the tidal parameters generally well within the standard deviations determined from the least squares adjustment in the tidal analysis. The deviations are in the range between 0×10−4 and 3×10−4 for the amplitude factor and the phases differ between 0.0005° and 0.01° for the four main tidal constituents O1, K1, M2, and S2.The comparison of the gravity residuals of the two sensors with each other as well as with their sum and difference in the time and frequency domain shows the existence of identical signals in the records of the two sensors in the whole range of observation. This probably means that either the environmental reductions applied are not sufficient or there are additional disturbing effects in the data which have not been taken care of yet. From the study it emerges that it is not possible to get entirely rid of the tidal signals in the data. This is probably also due to the fact that despite reductions the data sets contain additional signals and slightly different noise at tidal frequencies which affect the result of the tidal analysis. 相似文献
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Juergen Neumeyer Jan Hagedoorn Jens Leitloff Torsten Schmidt 《Journal of Geodynamics》2004,38(3-5):437
The redistribution of air masses induces gravity variations (atmospheric pressure effect) up to about 20 μgal. These variations are disturbing signals in gravity records and they must be removed very carefully for detecting weak gravity signals. In the past, different methods have been developed for modelling of the atmospheric pressure effect. These methods use local or two-dimensional (2D) surface atmospheric pressure data and a standard height-dependent air density distribution. The atmospheric pressure effect is consisting of the elastic deformation and attraction term. The deformation term can be well modelled with 2D surface atmospheric pressure data, for instance with the Green's function method. For modelling of the attraction term, three-dimensional (3D) data are required. Results with 2D data are insufficient.From European Centre for Medium-Range Weather Forecasts (ECMWF) 3D atmospheric pressure data are now available. The ECMWF data used here are characterised by a spacing of Δ and Δλ = 0.5°, 60 pressure levels up to a height of 60 km and an interval of 6 h. These data are used for modelling of the atmospheric attraction term. Two attraction models have been developed based on the point mass attraction of air segments and the gravity potential of the air masses. The modelling shows a surface pressure-independent part of gravity variations induced by mass redistribution of the atmosphere in the order of some μgal. This part can only be determined by using 3D atmospheric pressure data. It has been calculated for the Vienna Superconducting Gravimeter site.From this follows that the gravity reduction can be improved by applying the 3D atmospheric attraction model for analysing long-periodic tidal waves including the polar tide. The same improvement is expected for reduction of long-term absolute gravity measurements or comparison of gravity measurements at different seasonal times. By using 3D atmospheric pressure data, the gravity correction can be improved up to some μgal. 相似文献
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1978年5月使用了18台精度较高的重力仪在南京和北京分别建立了地震系统的重力检定场.本文结合以上成果和有关重力比较测定的资料, 从分析格值变化的各种因素及其产生的误差入手, 说明仪器格值标定的重要性和具体要求, 提出了选建地震系统重力检定场的方法技术和减小格值误差、提高测量精度的可能途径. 相似文献
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对天津蓟县地震台2套相对重力仪2018—2019年观测数据进行潮汐分析和提取非潮汐重力残差处理,研究水文变化所引起的重力响应。结果表明,蓟县地震台2套重力仪精度较高;GS-15重力仪重力残差与水文变化间存在较好的相关性,具体表现为降水时重力减少,降水结束后重力增大,水位下降时重力减少,水位上升时重力增大,但其间都存在延迟对应关系。 相似文献
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综述了近年内在全球地球动力学合作观测和研究网络框架下开展的重力场观测、频谱结构和应用研究方面的成果. 内容涉及精密大气、海潮负荷信号检测, 重力潮汐和自由核章动参数测定, 海潮模型和重力固体潮模型有效性检验, 重力潮汐实验模型构制, 地球球型基频和低阶震型谱峰分裂现象和地球Chandler摆动等方面. 文章还介绍了综合现代大地测量技术, 全球超导重力仪的长期、连续观测在地表水循环、同震和震后形变、地球慢形变和地壳垂直运动等方面将发挥重要作用的情况. 相似文献
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Long gravity records are of great interest when performing tidal analyses. Indeed, long series enable to separate contributions of near-frequency waves and also to detect low frequency signals (e.g. long period tides and polar motion). In addition to the length of the series, the quality of the data and the temporal stability of the noise are also very important. We study in detail some of the longest gravity records available in Europe: 3 data sets recorded with spring gravimeters in Black Forest Observatory (Germany, 1980–2012), Walferdange (Luxemburg, 1980–1995) and Potsdam (Germany, 1974–1998) and several superconducting gravimeters (SGs) data sets, with at least 9 years of continuous records, at different European GGP (Global Geodynamics Project) sites (Bad Homburg, Brussels, Medicina, Membach, Moxa, Vienna, Wettzell and Strasbourg). The stability of each instrument is investigated using the temporal variations of tidal parameters (amplitude factor and phase difference) for the main tidal waves (O1, K1, M2 and S2) as well as the M2/O1 factor ratio, the later being insensitive to the instrumental calibration. The long term stability of the tidal observations is also dependent on the stability of the scale factor of the relative gravimeters. Therefore we also check the time stability of the scale factor for the superconducting gravimeter C026 installed at the J9 Gravimetric Observatory of Strasbourg (France), using numerous calibration experiments carried out by co-located absolute gravimeter (AG) measurements during the last 15 years. The reproducibility of the scale factor and the achievable precision are investigated by comparing the results of different calibration campaigns. Finally we present a spectrum of the 25 years of SG records at J9 Observatory, with special attention to small amplitude tides in the semi-diurnal and diurnal bands, as well as to the low frequency part. 相似文献
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Accuracy assessment of ocean tide loading computations for precise geodetic observations 总被引：1，自引：0，他引：1
The increasing resolution of ground based gravity measurements (e.g. by superconducting gravimeters) as well as satellite based gravity field studies allows to study very small signals, globally as well as local. On the other hand, this requires the correction of such signals to uncover others. To study the Earth’s deep interior and the on-going dynamic processes requires the correction of disturbing signals, and one of these signals is related to ocean tidal loading. Although new ocean tide models are being derived from current satellite missions, there are still uncertainties.In this paper we present an intercomparison ocean tide models to test their fit to world-wide observations. Therefore, three TOPEX/POSEIDON (T/P) satellite derived models (CSR3.0, FES95.2 and TPXO.2) beside the classical SCHW80 model were selected for an accuracy assessment study. The selected models have been subjected to an intercomparison test, tide gauge validation test and comparison to 59 tidal gravity stations.The intercomparison test shows a good agreement between the T/P-based models for the open ocean and remarkable disagreement between the selected models in the coastal regions indicating that such models are still problematic in these regions. The tide gauge validation shows that the T/P derived models fit tide gauges better than SCHW80, with a better fit for the semidiurnal constituents than for the diurnal constituents. Comparing the gravimetric ocean-tide loading computed from the selected models with the residuals from a set of 59 tidal gravity stations shows that there is an improvement of the T/P derived models with respect to the Schwiderski model, especially in M2. However, this improvement is not as significant as the result of the comparison with the pelagic data. The procedure developed for the comparison of T/P derived models with SCHW80 is presented. The results provide not only information and improvement with regard to SCHW80, but also information about the properties of the new models. It is intended to continue this work applying the very recent models to see how they perform compared to this study.With this study we provide boundary conditions for the improvement of new ocean-tide models in order to benefit from the gravity measurements now possible regarding the evaluation of Earth structures and dynamic processes. 相似文献
11.
以中国大陆构造环境监测网络昆明台和恩施台gPhone相对重力仪连续重力潮汐观测数据为基础,研究了gPhone重力仪在1 mHz以上频段的高频响应。从瑞利面波角度获得gPhone重力仪的高频响应,并且通过与同址观测的STS-1地震仪LHZ分量数据进行对比,验证了gPhone重力仪高频观测结果的可靠性。对比从gPhone重力仪和STS-1地震仪观测数据中提取到的面波波形和群速度频散曲线,发现昆明台两类仪器观测到面波信号的振幅和相位都较为一致,而恩施台仅振幅较为一致,相位上存在较明显差异,gPhone重力仪记录的面波信号在各频段存在不同的时间延迟。用两类仪器观测数据获得了大地震激发的自由振荡,结果表明两类仪器观测到的基频球型模态自由振荡的频率和振幅都吻合较好,进一步验证了gPhone重力仪对高频频段信号振幅响应的可靠性。以上研究结果表明:利用gPhone重力仪能够准确地观测到大地震激发的面波和自由振荡等高频信号的振幅,但在记录信号的相位信息时,有些仪器会有相位偏移产生,如果研究中需要考虑信号的相位,则必须获得仪器相位偏移量,再进行仪器相位校正。 相似文献
12.
《Journal of Geodynamics》2007,43(4-5):159-174
The increasing resolution of ground based gravity measurements (e.g. by superconducting gravimeters) as well as satellite based gravity field studies allows to study very small signals, globally as well as local. On the other hand, this requires the correction of such signals to uncover others. To study the Earth’s deep interior and the on-going dynamic processes requires the correction of disturbing signals, and one of these signals is related to ocean tidal loading. Although new ocean tide models are being derived from current satellite missions, there are still uncertainties.In this paper we present an intercomparison ocean tide models to test their fit to world-wide observations. Therefore, three TOPEX/POSEIDON (T/P) satellite derived models (CSR3.0, FES95.2 and TPXO.2) beside the classical SCHW80 model were selected for an accuracy assessment study. The selected models have been subjected to an intercomparison test, tide gauge validation test and comparison to 59 tidal gravity stations.The intercomparison test shows a good agreement between the T/P-based models for the open ocean and remarkable disagreement between the selected models in the coastal regions indicating that such models are still problematic in these regions. The tide gauge validation shows that the T/P derived models fit tide gauges better than SCHW80, with a better fit for the semidiurnal constituents than for the diurnal constituents. Comparing the gravimetric ocean-tide loading computed from the selected models with the residuals from a set of 59 tidal gravity stations shows that there is an improvement of the T/P derived models with respect to the Schwiderski model, especially in M2. However, this improvement is not as significant as the result of the comparison with the pelagic data. The procedure developed for the comparison of T/P derived models with SCHW80 is presented. The results provide not only information and improvement with regard to SCHW80, but also information about the properties of the new models. It is intended to continue this work applying the very recent models to see how they perform compared to this study.With this study we provide boundary conditions for the improvement of new ocean-tide models in order to benefit from the gravity measurements now possible regarding the evaluation of Earth structures and dynamic processes. 相似文献
13.
Introduction The tidal variation signals of the solid Earth recorded with the modern measuring techniques can be used to provide effectively the means to cognize the Earths motion, deformation and structure character, especially to monitor the material motion in the Earths interior. In the recent 20 years, the distribution character of the global gravity field has made great progress since the continuous and deep theoretical studies in geophysics and geodesy domains. The successful manufactur… 相似文献
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The first phase (1997–2003) of the Global Geodynamics Project (GGP) has now been completed. Data from superconducting gravimeters (SGs) within GGP have shown great capabilities in a wide spectrum of geophysical applications from the tidal studies to the long-period seismology. Here, we compare the noise levels of the different contributing stations over the whole spectrum. We use three different processing procedures to evaluate the combined instrument-plus-site noise in the long-period seismic band (200–600 s), in the sub-seismic band (1–6 h) and in the tidal bands (12–24 h). The analysis in the seismic band has demonstrated that SGs are particularly well suited for the studies of the long-period normal modes and thus are complementary to long-period seismometers. In the sub-seismic band, the power spectral densities, computed over a period of 15 continuous days for every GGP station, cross the New Low Noise Model of Peterson from T = 16 min to T = 4.6 h. SG data are therefore appropriate for studying long-period seismic and sub-seismic modes. In the tidal bands, the noise comparison is realised by a least-squares fit to tides, local air pressure and instrumental drift, leading to gravity residuals where we estimate a standard deviation and average noise levels in different tidal frequency bands. Tidal gravity observations using SGs have also shown to be an independent validation tool of ocean tidal models, and they are therefore complementary to tide gauge and altimetric data sets. Knowledge of the noise levels at each station is important in a number of studies that combine the data to determine global Earth parameters. We illustrate it with the stacking of the data in the search for the gravity variations associated with the sub-seismic translational motions of the inner core, the so-called Slichter triplet. 相似文献
15.
Study on tidal gravity observations obtained at stations Zhongshan and Changcheng, Antarctic 总被引：1，自引：0，他引：1
Lü Chun-cao 《地震学报(英文版)》2001,14(3):325-332
IntroductionThe purpose of the studies on the tidal gravity observations on the Earth(s surface is to investigate the properties of the deformation and the tidal gravity variations of the Earth under the action of the luni-solar tidal force. These variations relate to the internal structure, shape and the medium(s rheology properties of the Earth (Wahr, 1981; Dehant, 1987). The theoretical studies and observations indicated that the amplitudes and the tidal parameters, including the amplitud… 相似文献
16.
本文对中比合作和我们独立获得的共10个台站17个仪器架次2890天的固体潮观测资料采用卡特莱特(Cartwright)的完全展开和维尼迪可夫(Venedikov)方法统一地进行了调和分析,并用中井(Nakai)方法对观测资料进行了拟合预处理以提高分析结果的信噪比,同时用线性内插方法处理了仪器灵敏度以资对比.本文着重讨论了分析结果所提供的我国大陆固体潮矢量空间分布的区域性特征及其与海洋负荷的关系.结果表明:中国大陆固体潮空间分布受到海洋负荷的明显控制.O1波尤为显着.文中讨论了仪器流变模型对观测矢量的影响.根据流变模型改正后的结果,所得到的地球对引潮力的实际响应的相位滞后,大多数发站都接近于-1,它论证了理论原则的正确性.文中还讨论了残差矢量与海洋负荷矢量的关系,它们的一致性最概括地说明了海洋负荷对固体潮的影响.文中用误差矢量的方法研究了分析结果的精度,它说明目前海潮改正的精度仍然是不够的.在上述工作基础上,文中最后得到了经海潮改正后的 M2波和 O1波的观测矢量. 相似文献
17.
用高精度重力技术检测地球自由核章动(FCN)参数(包括周期和Q值等)的难点是资料观测信噪比低,传统的方法是使用最小二乘拟合,但是获得的FCN共振参数精度不理想.本文利用武汉国际潮汐基准站高精度超导重力仪和全球超导重力仪观测的时变重力资料,根据贝叶斯算法拟合地球自由核章动(FCN)参数.我们将贝叶斯拟合方法与传统最小二乘法实施了对比分析,研究了不同台站资料差异.讨论了潮波选择和不同海潮模型等因素对FCN参数的影响.结果表明用贝叶斯算法获得的FCN品质因子与空间大地测量VLBI结果吻合的更好,这说明贝叶斯算法可靠性高,为研究地球深内部构造参数(核幔边界粘滞系数等)提供了有效依据. 相似文献
18.
Olivia Jensen Jacques Hinderer David J. Crossley 《Physics of the Earth and Planetary Interiors》1995,90(3-4)
In recent years, several claims of detection of weak harmonic signals in the sub-tidal band of frequencies of high-quality gravimeter data have been made. Here, we review our attempts at confirming Smylie's claim of detection of the Slichter mode of inner-core oscillation using the same four data sets he and his colleagues used. We further examine the homogeneous 2 year data sets obtained from the superconducting gravimeters sited in Strasbourg and at Cantley, Quebec. We show that the power spectra of tidal-reduced, pressure and slew-corrected gravity residuals from these data are indistinguishable from a random walk process except in narrow bands dominated by residual earth tides and by harmonics of the diurnal thermal-atmospheric tide. Such a random ‘brown’ residual could result from mechanical instabilities and electronic noise in the instruments themselves, from site-specific tectonic noise, from local hydrological variations and pier instabilities or it could derive from unaccounted for variability in the atmospheric pressure in the vicinity of the instruments. We argue that the homogeneous 2 year data sets show no evidence whatever of Slichter harmonics even though our preprocessing methods reduce ‘apparent noise levels’ in the core-mode band by almost an order magnitude in comparison with the four data sets originally employed by Smylie et al. and, in their first attempted confirmation of his claimed discovery, by Jensen et al. 相似文献
19.
《Journal of Geodynamics》2010,49(3-5):325-330
The network of superconducting gravimeters (SG) of the ‘Global Geodynamics Project’ (GGP) offers the unique opportunity to supplement and validate the gravity field variations derived from the GRACE satellite mission. Because of the different spatial and temporal resolutions of the gravity data a combination of all datasets can be used to retrieve a maximum of information regarding mass transfers especially related to hydrology which is deployable as constraint for hydrological modelling.For a consistent combination of the datasets the gap between terrestrial data of superconducting and absolute gravimeters (AG) and from satellite data has to be bridged. A successful combination of SG and AG data could be realized for several stations which resulted in time series of the highest accuracy and long-term stability.In principle, the same reductions applied to GRACE data have to be taken into account for the terrestrial data. The separation of local hydrological effects in SG observations is crucial for the comparison with satellite-derived gravity data. It is shown that even for stations with a hydrological challenging situation such as Moxa/Germany local hydrology-induced effects can be successfully modelled.Currently, the study focuses on Europe with its dense and long-term observation network. Regarding the consistency of the SG gravity variations they are representative for a larger region. From a comparison with GRACE-derived gravity field changes, and the variations due to hydrological models a principle good agreement emerges. 相似文献
20.
The synthetic tidal parameters with high spatial resolution for gravity over China and its neighbor area are con- structed with Earth’s tidal model and ocean tide loading calculated using TPXO7 global ocean tide model as well as tidal data over China seas. The comparison between synthetic parameters and ones observed by spring gravime- ters at some seismic network stations and Hong Kong station and one observed by super-conducting gravimeter at Wuhan station shows that the average differences in amplitude factors and phases are smaller than 0.005 and 0.5° respectively; and that the discrepancies between observational and synthetic parameters are dependent on gravim- etric technique in that the synthetic parameters are in well agreement with the superconducting gravimetric obser- vations. This also indicates that the synthetic result is a good estimation for tidal gravity, and the numerical results in the present paper not only can provide ground and space gravimetry such as absolute gravimetry with correction model of tidal gravity, but also provide effective tidal parameters over areas where no observation is carried out. 相似文献