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《武汉大学学报(信息科学版)》2016,(8)
观测地球内核平动振荡Slichter模有助于约束地球内部结构,但其探测仍是国际性难题。基于全球分布的9个超导重力(Superconductiug Gravimeter,SG)台站的11个观测序列,利用最优序列估计(optimal sequence estimation,OSE)方法进行了探测实验。首先利用模拟的11个SG台站记录验证了OSE方法的有效性,然后将OSE方法用于剔除潮汐及气压等影响后的实测重力残差数据,但所得结果中仍残留有高阶潮波信号。针对此,利用解调过程进一步剔除了这些信号,以消除对目标信号识别的影响。最终结果表明,没有发现Smylie于1992年发表论文中所声称的观测结果,但找到了另外一组满足分裂规律的可能信号,其周期分别为4.310±5.7×10-3 h(m=-1)、3.914±6.4×10-3 h(m=0)和3.642±5.1×10-3 h(m=+1)。该组信号很可能是Slichter模三重分裂信号,但仍需进一步验证。 相似文献
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内核存在约(0.27°~0.53°)/a的超速旋转,由此导致的全球年平均重力变化强度约为0.08~0.16μGal(0.8~1.6 nms-2)。除地震数据外,时变重力数据有可能成为探测内核超速旋转速率的重要信息源。对武汉九峰台站超导重力仪观测数据进行了潮汐改正、大气负荷改正、极移改正和日长变化改正,得到了经过各项改正后的时变重力信号;采用小波分析方法对上述时变重力信号进行了处理分析,得到了可供参考的结果;针对目前利用超导重力仪数据探测内核超速旋转所存在的困难提出了几个解决方案和建议。 相似文献
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针对基于沿海GPS站点坐标时间序列反演海潮负荷特征信息研究较少的问题,提出利用FFT与HHT提取海潮负荷信息,两种频谱方法原理各异,但都可将目标信息从原始数据中分离出。基于沿海站点的坐标时间序列,经小波去噪后进行海潮分潮特征信息提取试验,最后与3种全球海潮模型FES2004、NAO.99b和GOT4.7的模型值比较,评估两种方法的反演精度,结果显示:HHT、FFT都能够准确探测到海潮分潮信号,FFT全日潮周期反演结果优于HHT反演结果,半日潮周期反演精度相当;HHT边际谱的谱值为对应频率出现的可能程度,无法与模型值进行比较,而FFT振幅值为绝对值,其结果与模型值符合情况良好;在探测未知信号时,FFT可能会探测出虚假信号,而HHT更能真实反映信号的组成。 相似文献
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利用Canberra、Matsushiro、Membach和Metsahovi 4个台站2008年5月的超导重力数据对汶川8.0级大地震激发的球型地球自由振荡进行了研究。结果表明,0S0~0S48全部基频振型以及1S4、2S4和3S13个谐频振型与PREM模型的误差在0.02‰~1.93‰,且所有振型的信噪比均大于阈值3,表明本文的计算方法是有效的,计算结果是可信的;0S2、0S3和0S4存在谱线分裂现象,其谱线分裂率R为1.093 40、0.674 30和1.071 00,验证了地球自转和椭率是引起0S2、0S3和0S4谱线分裂的主要原因。 相似文献
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为了充分利用多光谱图像的光谱信息和全色图像的空间信息,本文提出一种基于深度递归残差网络的遥感图像空谱融合方法。方法将残差网络和递归网络相结合,利用残差网络学习低空间分辨率多光谱图像与高空间分辨率多光谱图像之间的残差,同时结合全局残差和局部残差,加快网络的收敛速度,解决深层次网络容易出现的梯度消失和梯度爆炸问题;利用递归神经网络在不增加权重参数、减轻过拟合的情况下通过提高网络层数来提高精度,得到更好的图像融合效果。为了验证本文方法的有效性,应用遥感图像进行模拟实验、真实实验和泛化实验,实验结果与传统方法和现有深度学习方法进行对比分析。主观视觉和客观定量评价表明,本文方法很好地改善了传统方法存在的光谱失真现象,并且较现有深度学习方法学习到更深层次丰富的图像特征,更好地保留了图像的空谱信息,同时泛化实验也说明本文的网络具有较好的泛化能力。 相似文献
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东日本大地震重力信号同震响应 总被引:2,自引:0,他引:2
对2011年3月11日日本本州东海岸附近海域Mw9.0级地震前后的观测重力资料进行了同震响应信号分析,给出了gPhone重力仪在大地震后的长周期地震面波和自由振荡的观测结果。震后12h数据经带通滤波后可以分辨出7个环绕地球传播的瑞雷波记录,在低频范围内(5mHz以下)检测到43个地球自由振荡基频振型及52个谐频振型,其分布与理论模型吻合较好。其中,在1mHz以下的低频段内观测到4个振型的谱峰分裂现象。 相似文献
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利用局部重力数据改进重力场模型 总被引:4,自引:2,他引:4
本文系统论述了利用局部重力数据对已知重力场模型位系数加以改进的理论和方法,问题的实质是重力异常和位系数两类数据的综合利用,文中给出了联合平差和局部积分改进两种方法,重点讨论了局部积分改进的位系数改正数的谱权综合法,并给出了数值试验结果。 相似文献
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针对月核大小及密度估计问题,利用高分辨率重力场模型GL1500E的二阶位系数和LLR(lunar laser ranging)天平动参数,考虑月核分层为外核和内核的情况,结合非线性粒子群优化算法,对月核大小和组成进行了估计。大批量的统计结果表明,大概率分布的外核半径rc1约为469 km,内核半径rc2约为303 km,外核密度ρc1约为4613 kg/m3,内核密度ρc2约为7004 kg/m3,月幔密度ρm约为3340 kg/m3。月幔密度非常接近地质研究结果3360 kg/m3,内外核半径与近期其他研究结果相近,估算的月核大小与密度组成具有一定的参考价值。若月核由纯铁和硫化亚铁组成,则研究表明,内核大部分由纯铁组成,外核大部分由硫化亚铁组成。 相似文献
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Due to the super rotation of the Earth’s inner core, the tilted figure axis of the inner core would progress with respect to the mantle and thus cause the variation of the Earth’s external gravity field. This paper improves the present model of the gravity field variation caused by the inner core super rotation. Under the assumption that the inner core is a stratifying ellipsoid whose density function is fitted out from PREM and the super rotation rate is 0.27~0.53°/yr, calculations show that the global temporal variations on the Earth’s surface have a maximum value of about 0.79~1.54×10?3 μGal and a global average intensity of about 0.45~0.89×10?3 μGal in the whole year of 2007, which is beyond the accuracy of the present gravimetry and even the super conducting gravimeter data. However, both the gravity variations at Beijing and Wuhan vary like sine variables with maximal variations around 0.33 μGal and 0.29 μGal, respectively, in one cycle. Thus, continuous gravity measurements for one or two decades might be able to detect the differential motion of the inner core. 相似文献
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Short-wavelength Spectral Properties of the Gravity Field from a Range of Regional Data Sets 总被引:1,自引:0,他引:1
Jakob Flury 《Journal of Geodesy》2006,79(10-11):624-640
The GRACE (gravity recovery and climate experiment) and GOCE (gravity field and steady-state ocean circulation explorer) dedicated gravity satellite missions are expected to deliver the long-wavelength scales of the Earth’s gravity field with extreme precision. For many applications in Earth sciences, future research activities will have to focus on a similar precision on shorter scales not recovered by satellite missions. Here, we investigate the signal power of gravity anomalies at such short scales. We derive an average degree variance and power spectral density model for topography-reduced gravity anomalies (residual terrain model anomalies and de-trended refined Bouguer anomalies), which is valid for wavelengths between 0.7 and 100 km. The model is based on the analysis of gravity anomalies from 13 test regions in various geographical areas and geophysical settings, using various power spectrum computation approaches. The power of the derived average topography-reduced model is considerably lower than the Tscherning–Rapp free air anomaly model. The signal power of the individual test regions deviates from the obtained average model by less than a factor of 4 in terms of square-root power spectral amplitudes. Despite the topographic reduction, the highest signal power is found in mountainous areas and the lowest signal power in flat terrain. For the derived average power spectral model, a validation procedure is developed based on least-squares prediction tests. The validation shows that the model leads to a good prediction quality and realistic error measures. Therefore, for least-squares prediction, the model could replace the use of autocovariance functions derived from local or regional data. 相似文献
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地幔纬向正常密度函数 总被引:7,自引:0,他引:7
继"地球纬向正常密度假说"和"板块运动纬向重力模式"的提出之后,以参数椭球为工具,应用求解"地球纬向正常密度函数"的数学方法,在假设地核为匀质椭球和地壳并入地幔的前提下,初步求解出满足极点与赤道重力条件的"地幔纬向正常密度函数",从而使得"地幔纬向密度异常"的提法在理论上获得了依据. 相似文献
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Erik de Min 《Journal of Geodesy》1995,69(4):223-232
Summary Basically two different evaluation methods are available to compute geoid heights from residual gravity anomalies in the inner zone: numerical integration and least squares collocation.If collocation is not applied to a global gravity data set, as is usually the case in practice, its result will not be equal to the numerical integration result. However, the cross covariance function between geoid heights and gravity anomalies can be adapted such that the geoid contribution is computed only from a small gravity area up to a certain distance
o from the computation point. Using this modification, identical results are obtained as from numerical integration.Applying this modification makes the results less dependent on the covariance function used. The difference between numerical integration and collocation is mainly caused by the implicitly extrapolated residual gravity anomaly values, outside the original data area. This extrapolated signal depends very much on the covariance function used, while the interpolated values within the original data area depend much less on it.As a sort of by-product, this modified collocation formula also leads to a new combination technique of numerical integration and collocation, in which the optimizing practical properties of both methods are fully exploited.Numerical examples are added as illustration. 相似文献
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Due to the super rotation of the Earth's inner core, the tilted figure axis of the inner core would progress with respect to the mantle and thus cause the variation of the Earth's external gravity field. This paper improves the present model of the gravity field variation caused by the inner core super rotation. Under the assumption that the inner core is a stratifying ellipsoid whose density function is fitted out from PREM and the super rotation rate is 0.27-0.53°/yr, calculations show that the global temporal variations on the Earth's surface have a maximum value of about 0.79-1.54×10^3 pGal and a global average intensity of about 0.45-0.89×10^ 3 μGal in the whole year of 2007, which is beyond the accuracy of the present gravimetry and even the super conducting gravimeter data. However, both the gravity variations at Beijing and Wuhan vary like sine variables with maximal variations around 0.33 pGal and 0.29 pGal, respectively, in one cycle. Thus, continuous gravity measurements for one or two decades might be able to detect the differential motion of the inner core. 相似文献
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本文所采用的基于输入-输出系统论的谱方法在计算结果的精度上与最小二乘配置方法相当,却很容易用于异性场的计算。用该谱方法对卫星测高及海洋重力资料进行组合求解重力场量(大地水准面差距和重力异常),其误差估计结果表明各向异性场的计算精度优于各向同性场的精度。 相似文献
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运用Hilbert-Huang变换(HHT)从时频域的角度对大坝监测资料进行了分析。通过经验模态分解(empirical mode decomposition,EMD),测值序列被分解为以不同频率波动的内在模态分量(IMF)和代表序列变化趋势性的余量,其分解所得的各IMF分量的变化具有调幅调频特征,余量则可以反映测值趋势性变化的局部特征。效应量和环境量测值的Hilbert谱存在一定的相似性,测值变化的调幅调频特征反映了大坝、基岩和周围环境组成的复杂系统的非线性和非平稳性。 相似文献
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针对传统的遥感图像融合方法通常会引起光谱失真的问题和大多数基于深度学习的融合方法忽略充分利用每个卷积层信息的不足,本文结合密集连接卷积网络和残差网络的特性,提出了一个新的融合网络。该网络通过建立多个密集卷积块来充分利用卷积层的分级特征,同时块与块之间通过过渡层加快信息流动,从而最大程度地对特征进行极致利用并提取到丰富的特征。该网络应用残差学习拟合深层特征与浅层特征之间的残差,加快网络的收敛速度。实验中利用GaoFen-1(GF-1)和WorldView-2/3(WV-2/3)的多光谱图像MS (Multispectral Image)和全色图像PAN(Panchromatic Image)(MS与PAN的空间分辨率之比为4)评估本文提出方法的有效性。从视觉效果和定量评估结果两个方面来看,本文方法得到的融合结果要优于所对比的传统方法和深度学习方法,并且该网络具有鲁棒性,能够泛化到不需要预训练的其他卫星图像。本文方法通过特征的重复利用实现了光谱信息的高保真并提高了空间细节分辨能力,有利于遥感图像的应用研究。 相似文献