日本M9.0地震后云南测震数据中

2011-03-11日本M9.0地震后引发的地球自由振荡在测震和地倾斜观测数据中同时出现。其中，测震记录中出现大量低频长周期信号，这些信号的频率在地震计的通频带之外，难以用常规的地震计理论来解释。为判断该信号是地面倾斜还是地面平动，将该长周期信号分别假设为平动及倾斜信号，基于观测系统模型对整个观测过程进行仿真。结果表明， 日本9.0级地震后，洱源台测震数据中周期约为390 s（6.5 min）的通带外信号主要来源于地震计对地面倾斜的响应而非平动。

Interpretation to Out of Pass-Band Signals in Broadband Seismometer Data for the Tohoku Earthquake of M9.0 in 2011

On March 11,2011, an earthquake of magnitude of 9.0 occurred at Japan. Earth’s free oscillation and teleseismic surface waves caused by this earthquake are recorded by both tiltermeters and seismometers in Yunnan province, China. Some low-frequency signals, which are out of the seismometer’s pass-band, appear in seismic data and cannot be easily interpreted by classic seismological theory. By assuming the trigger signals as translation motion and tilt motion individually, the records of seismometer are simulated by a mathematic seismometer model. We argue that the signal out of the seismometer’s pass-band recorded at Eryuan station, of which the period is 390 s(6.5 min), is the response of seismometer to tilt motion, not to translating motion.