We first studied Earth s free torsional oscillation using observed data of JCZ-1 seismometer. JCZ-1 seismometer at the Wuhan Observation Station has observed the Earth's free oscillations excited by the great 2011 Japan earthquake, the great 2010 Chile earthquake and the great 2005 Indonesia earthquake, we detected the eigen periods of basic and first mode: 0T2~0T67 and 1T2~1T50, and error ratio is less than 0. 5% by comparing with the PREM theoretical eigenvalues. We also complemented some modes: 0T11 , 0T15, 0T19, 1T4, 1T5, 1T14, which are not mentioned in PREM, and observed the multi-peak phenomenon of 0T2, 0T6, oT7和0T8. The results show that JCZ-1 seismometer can precisely observe ultralow frequency and long period free oscillations of the Earth.%本文首次采用JCZ-1型地震仪观测资料研究地球环型自由振荡,并在2011年日本9.0级地震、2010年智利8.8级地震和2005年印尼8.6级地震后武汉地震台JCZ-1型地震仪观测到了其激发的环型自由振荡,从中检测了基振型0T2～0T67和一次振型1T2～1T50等振型的本征周期,与PREM的理论值比较,误差比小于0.5％,补充了PREM中未提到的几次振型的本征周期:0T11、0T15、0T19、1T4、1T5、1T14,并观测到了日本地震0T2、0T6、0T7和0T8振型的多峰值现象.研究结果表明,JCZ-1型地震仪具有良好的观测超低频长周期地球自由振荡的能力.
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