摘要
采用全球地球动力学计划观测网中 13台超导重力仪长期连续观测资料 ,探讨了长周期核模检测的可能性 .采用相同的方法剔除了所有 13个观测序列中的重力潮汐信号、仪器漂移和大气重力信号 ,估计了各个序列的功率谱密度及其积谱密度 ,估计并分析了非潮汐不同频段背景噪声 .结果表明 ,在两个潮汐间频段 (0 0 4 7～0 0 75cph和 0 0 89～ 0 117cph)和亚潮汐频段 (0 172～ 0 333cph) ,全球超导重力仪的平均噪声水平分别为 0 0 6 4 9,0 0 35 0nm s2 和 0 0 138nm s2 ,可以检测到的全球谐信号幅度极限分别为 0 0 4 16 ,0 0 2 31nm s2 和 0 0 0 98nm s2 ,表明全球超导重力仪观测资料基本可以识别长周期核模信号 .在全球超导重力观测中 ,在潮汐间频段发现周期分别16 5 5 ,15 79,11 0 0h和 10 0 9h的全球谐信号谱峰 ,可能来自于液核长周期振荡 ;在亚潮汐频段没有Smylie 1992年发现的Slichter模信号 ,但存在 8个全球谐信号的谱峰 ,参考现有的理论模拟结果 ,Slichter模是这些信号可能的来源之一 .
Possibility of detection of the long-period core modes is discussed by using the long-term gravity observations recorded with 13 superconducting gravimeters (SGs) in a worldwide network of the Global Geodynamics Projects. Identical techniques are used to remove the luni-solar gravity tides, the long-term trends of instrument drift, and the effects of atmospheric pressure from all 13 SG data sets. The power spectral density of each data set, as well as the product spectral density of all the data sets, is evaluated. The background noise levels in various non-tidal bands are estimated and analyzed. The results indicate that the background noise level of the global SG observations is 0 0649 nm/s2 in the inter-tidal band from 0 047 to 0 075cph, 0 0350 nm/s2 in another inter-tidal band from 0 089 to 0 117cph, and 0 0138 nm/s2 in the sub-tidal band from 0 172 to 0 333cph. The magnitude thresholds of any global harmonic signals, which may be detected by the global SGs, in these three non-tidal bands are 0 0416, 0 0231and 0 0098 nm/s2, respectively. It implies that the signals, related to the long-period core modes, may be identified in the global SG observations, if they exist. The spectral peaks of the global harmonic signals with periods of 16 55, 15 79, 11 00 and 10 09h are detected in the two inter-tidal bands of the global SG records; and they may come from the long-period oscillations in the fluid outer core of the Earth. In the sub-tidal band, there is no obvious peak relating to the Slichter triplet claimed by Smylie in 1992 Instead, 8 spectral peaks of global harmonic signatures significantly emerge from the background noise. Comparing their periods with those of the Slichter triplet predicted theoretically, it may be concluded that the Slichter triplet is one of the possible resources of three peaks of them.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2005年第1期69-77,共9页
Chinese Journal of Geophysics
基金
国家自然科学基金项目 (4 0 1740 2 2 )
中国科学院知识创新工程项目 (KZCX3 SW 13 1)
中国科学院百人计划资助
关键词
全球地球动力学计划
超导重力仪
长周期核模
积谱密度
Global Geodynamics Projects, Superconducting gravimeters, Long-period core modes, Product spectral density
