东日本大地震重力信号同震响应

对2011年3月11日日本本州东海岸附近海域Mw9.0级地震前后的观测重力资料进行了同震响应信号分析,给出了gPhone重力仪在大地震后的长周期地震面波和自由振荡的观测结果。震后12h数据经带通滤波后可以分辨出7个环绕地球传播的瑞雷波记录,在低频范围内(5mHz以下)检测到43个地球自由振荡基频振型及52个谐频振型,其分布与理论模型吻合较好。其中,在1mHz以下的低频段内观测到4个振型的谱峰分裂现象。

Coseismic Response to Gravity Signals of the Great Earthquake in East Japan

We analyze the gravity data observed before and after March 11,2011 when the Mw9.0 earthquake occurred in the sea areas nearby the East coast of Honshu,Japan,with the method of co-seismic response signal analysis.We also provide the observations of long-period seismic surface waves and free oscillations recorded by gPhone gravimeter after the great earthquakes.Processed by band-pass filter,the data obtained within 12 hours after the earthquake can be recognized the records of 7 Rayleigh surface waves spreading around the Earth.In the low frequency domain(5 mHz or less),43 fundamental modes and at least 52 harmonic modes of Earth's free oscillations can be detected,the distributions of which are in good agreement with the theoretical modes.Meanwhile,at the low frequencies less than 1 mHz,spectral splitting of 4 modes is observed.