gPhone重力仪的面波频段响应实测研究

以中国大陆构造环境监测网络昆明台和恩施台gPhone相对重力仪连续重力潮汐观测数据为基础,研究了gPhone重力仪在1 mHz以上频段的高频响应。从瑞利面波角度获得gPhone重力仪的高频响应,并且通过与同址观测的STS-1地震仪LHZ分量数据进行对比,验证了gPhone重力仪高频观测结果的可靠性。对比从gPhone重力仪和STS-1地震仪观测数据中提取到的面波波形和群速度频散曲线,发现昆明台两类仪器观测到面波信号的振幅和相位都较为一致,而恩施台仅振幅较为一致,相位上存在较明显差异,gPhone重力仪记录的面波信号在各频段存在不同的时间延迟。用两类仪器观测数据获得了大地震激发的自由振荡,结果表明两类仪器观测到的基频球型模态自由振荡的频率和振幅都吻合较好,进一步验证了gPhone重力仪对高频频段信号振幅响应的可靠性。以上研究结果表明:利用gPhone重力仪能够准确地观测到大地震激发的面波和自由振荡等高频信号的振幅,但在记录信号的相位信息时,有些仪器会有相位偏移产生,如果研究中需要考虑信号的相位,则必须获得仪器相位偏移量,再进行仪器相位校正。

Study with Observations on Responses of gPhone Gravimeters at Surface Wave Frequency Band

Based on the continuous gravity tides data recorded by the gPhone relative gravimeters at Kunming and Enshi stations in the Crustal Movement Observation Network of China(CMONOC),we analyzed high frequency responses above 1 mHz of gPhone gravimeters.Different from previous studies,we obtained high frequency responses of gPhone gravimeters from the view of Rayleigh wave,and by comparing with the results of the LHZ component data of the STS-1 seismometer observed at the same site at the Kunming and Enshi stations,we also tested the reliability of the high frequency results of gPhone gravimeters.Through comparing surface waveforms and dispersion curves extracted by the two different instruments,we find that the amplitudes and phases of surface waves are consistent observed by the two different instruments at Kunming station,and the amplitudes of surface waves are consistent,but the phases of surface waves are different at the Enshi station.There are different time delays in different frequency bands for surface waves recorded by the gPhone gravimeter at the Enshi station.Moreover,the results of the Earth’s free oscillations excited by a large earthquake recorded by the two different instruments show that the frequencies and amplitudes of the fundamental frequency spherical free oscillation are in good agreement,which further proves the reliability of the high frequency amplitude responses of gPhone gravimeters.The results in this study reveals that the amplitudes of high frequency signals,such as surface waves and free oscillations excited by large earthquakes,can be accurately recorded by gPhone gravimeters.However,when recording the phase information of signals,some gPhone gravimeters may cause phase delay.If the phases of signals need to be considered,we should obtained the phase delay caused by the gPhone gravimeter,then corrected the time delay(phase delay)of the recorded signals.