中文摘要：

基于拉萨超导重力仪（SG）4a的连续观测数据计算其在地震频段（200-600s）的背景噪声水平,并研究气压、采样率等对功率谱密度（PSD）的影响。分析比较全球地球动力学计划（GGP）公布的2013年全球SG在地震频段和亚地震频段的背景噪声水平,结果发现：1）在频率低于10-3 Hz时,潮汐和气压改正可以很好地改进重力PSD;2）在频率低于0.5×10-3 Hz时,超导重力仪的噪声水平明显优于地震仪,表明SG更适合研究长周期地震和亚地震模;3）全球SG地震频段噪声水平的范围为0.180~1.964,亚地震频段噪声水平的范围为1.860-3.853。

英文摘要：

The background noise level in seismic frequency band（200-600s）based on four years continuous observation of superconducting gravimeter（SG）at Lhasa station is investigated,and the influence of power spectral density（PSD）caused by atmosphere and sampling rate is also studied.The noise level of SG observation provided by global geodynamic project（GGP）for 2013 in seismic frequency band and sub-seismic frequency band are calculated,and they are further analyzed and compared.It is found that the PSD of gravity can be improved by tides and atmosphere correction when the frequency is below 10-3 Hz.When the frequency is below 0.5×10-3 Hz,the noise level of SG is obviously better than that of a seismometer.This means that SG is more suitable for researching longperiod seismic and sub-seismic modes.The range of the seismic noise magnitude of global SG is 0.180-1.964,and the range of sub-seismic noise magnitude is 1.860-3.853.