利用常熟地震台同场地形变仪记录检测对比地球自由振荡信号

利用常熟地震台同场地观测的洞体应变仪、体应变仪、水管倾斜仪、垂直摆倾斜仪记录数据，采用小波变换与功率谱密度估计方法，检测2011年3月11日日本9.0级大地震激发的地球自由振荡信号，其中检测到47个球型基频振型（₀S₃—₀S₄₉）、15个环型基频振型（₀T₅—0T₂₅）以及部分球型谐频振型，与地球初步参考模型（PREM）理论频率值基本符合，表明检测结果较好。对比结果显示：水管倾斜仪检测球型振荡振型能力最强，垂直摆倾斜仪检测环型振荡振型能力最强；体应变仪可检测到清晰的环型基频振型，且信噪比较高；倾斜仪对自由振荡信号的检测能力优于应变仪。

Detection and comparison of the earth free oscillation signals by using the same field topographic deformation records at Changshu Seismic Station

Using the same field observations of the tunnel body strain gauge, volume strain gauge, water-tube tiltmeter, and vertical pendulum tiltmeter at Changshu Seismic Station, the earth free oscillation signals excited by the magnitude 9.0 earthquake in Japan on March 11, 2011, is detected by using the wavelet transform and power spectral density estimation methods, in which 47 spheroidal fundamental frequency modes (₀S₃—₀S₄₉) and 15 torsional fundamental frequency modes (₀T₅—0T₂₅) are detected. Some spheroidal harmonic modes are basically consistent with the theoretical frequency value of the preliminary earth reference model (PREM), indicating that the detection results are good. The comparison results show that the water-tube tiltmeter has the strongest ability to detect the spheroidal oscillation mode, and the vertical pendulum tiltmeter has the strongest ability to detect the torsional oscillation mode; The volume strain gauge can detect clear torsional fundamental frequency modes with high signal-to-noise ratio; The ability of inclinometer to detect free oscillation signal is better than that of strain gauge.