利用张家口地震台体应变观测资料检测地球自由振荡

在保证低频自由振荡信号分辨率，又不对高频自由振荡信号产生抑制效应的前提下，利用张家口地震台体应变观测资料，采用功率谱密度估计方法，获得2011年3月11日日本9.0级大地震激发的₀S₂-₀S₇₄基频球型振荡和17个谐频球型振荡（₃S₂、₅S₃、₂S₁₀、₂S₁₂、₃S₉、₁₁S₁、₇S₁₀、₅S₁₃、₄S₁₈、₅S₁₄、₁₄S₄、₄S₂₄、₁S₃₈、₇S₁₈、₁₄S₈、₉S₁₉、₅S₃₀），并与地球初步参考模型（PREM）的理论自由振荡周期进行对比，发现与实测振荡周期基本一致。

Detection of Earth's free oscillations by using body strain observation data at Zhangjiakou Seismic Statoin

Under the conditions of ensuring the resolution ratio of low frequency free oscillation signals and no inhibiting effect on high frequency free oscillation signals, we acquired ₀S₂-₀S₇₄ fundamental sphere free oscillations and 17 harmonic sphere free oscillations ₃S₂、₅S₃、₂S₁₀、₂S₁₂、₃S₉、₁₁S₁、₇S₁₀、₅S₁₃、₄S₁₈、₅S₁₄、₁₄S₄、₄S₂₄、₁S₃₈、₇S₁₈、₁₄S₈、₉S₁₉、₅S₃₀ caused by the March 11,2011 Japan earthquake using the digital observation data of the strain meter at Zhangjiakou Seismic Station by power spectrum density estimation method. Compared it with the periods of free oscillations of the PREM model, it is found that the measured oscillation period is basically coincide with the oscillation period predicted by the PREM model.