MONUMENT MOTION AND MEASUREMENTS OF CRUSTAL VELOCITIES
MONUMENT MOTION AND MEASUREMENTS OF CRUSTAL VELOCITIES
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DOI：
10.1029/95gl02661
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发表时间：
1995-11-01
影响因子：
5.2
通讯作者：
AGNEW, DC
中科院分区：
文献类型：
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作者：
JOHNSON, HO;AGNEW, DC
在大地测量研究中通常假设测量误差与下一次测量无关，并且变形率（速度）在实验期间是恒定的。测量之间的任何时间相关性都可以在从测量的时间序列确定速度估计时显著影响速度估计的不确定性。一个可能的长期来源。相关性是大地测量纪念碑相对于“深"地壳的运动。可用的测量表明，这种运动引入了具有随机游走过程形式的误差。我们展示了这种错误如何影响速度估计的不确定性。对于设定持续时间的大地测量实验，我们计算速度不确定性作为观测次数和相关和不相关噪声的相对量的函数。我们发现，1）忽略长期的时间相关性，使估计的速度的不确定性太小，2）当相关和独立的噪声源是类似的幅度，预期的改善不确定性有更多的测量（1/根N）没有实现，在某些情况下几乎没有改善。我们还检查了异常值（“失误”）对速度不确定性的影响;对于大地测量场典型的异常值频率，前面的两个结论仍然存在。这些结果表明，长期相关性对估计变形率有很大影响;除非这些相关性很小，否则频繁的观测几乎没有什么优势。如果频繁的观测计划，相关噪声的量，由于纪念碑不稳定性必须保持小，如果要实现测量技术的全部能力。
It is usually assumed in geodetic studies that measurement errors are independent from one measurement to the next and that the rate of deformation (velocity) is constant over the duration of the experiment. Any temporal correlation between measurements can substantially affect the uncertainty in this velocity estimate when it is determined;from the time series of measurements. One source of possible long-term. correlation is motion of the geodetic monument with respect to the ''deep'' crust. Available measurements suggest that this motion introduces errors that have the form of a random walk process. We show how such errors affect the uncertainty of velocity estimates. For a geodetic experiment of set duration we calculate the velocity uncertainty as a function of the number of observations and of the relative amount of correlated and uncorrelated noise. We find that 1) neglecting long-term temporal correlations makes the uncertainty in the estimated velocities much too small, and that 2) when the correlated and independent noise sources are of similar magnitude, the expected improvement in uncertainty from having more measurements (1/root N) is not realized; there is almost no improvement in some cases. We have also examined the effect of outliers (''blunders'') on the velocity uncertainty; for a frequency of outliers typical of geodetic field the previous two conclusions remain These results suggest that long-term correlations have a large effect on estimating deformation rates; unless these correlations are small, frequent observations give little advantage. If frequent observations are planned, the amount of correlated noise due to monument instability must be kept small if the full capabilities of the measurement technique are to be realized.