| Gravity measurement is of great significance to the study of geodynamics,the fine structure of the earth's interior,and resource exploration.The current observation results show that the analysis of the impact of environmental disturbances on gravity observation data is indispensable in the study of gravity measurement data.In this paper,based on the data of the i Grav-012 superconducting gravimeter from June to October in 2016,2018,2019 and 2020,the disturbance data of superconducting gravity observations are studied for the three large-scale disturbance sources of earthquakes,typhoons,and infragravity waves.Extract the corresponding disturbance signals in the superconducting gravity observation data and carry out time-frequency feature analysis to provide technical support for the processing of gravity measurement data.The main research results are as follows:(1)Combining the seismic data to screen out the seismic events with no obvious co-seismic changes within 3 hours before and after the earthquake,the spectral analysis results of the superconducting gravity observation data before,after the earthquake,and the co-seismic period and the earthquake quiet period exceeded.Based on the results of spectrum analysis of guided gravity observation data,it explores the variation characteristics of the dominant frequency band with the magnitude and epicenter distance of the disturbance signal of the seismic event on the superconducting gravity observation data.The study found that within 3 hours before the earthquake,the superconducting gravity observation data showed obvious dominant frequency bands at 0.205 Hz,0.132 Hz,and 0.068 Hz;the dominant frequency bands during the co-seismic period were concentrated in 0.207 Hz,0.115 Hz and 0.056 Hz;after the earthquake within 3 hours,the dominant frequency bands were concentrated in 0.204 Hz,0.136 Hz and0.057 Hz.The results of spectral analysis of superconducting gravity observation data during the quiet period of the earthquake show that although there are also three dominant frequency bands in this period,the low frequency band in the quiet period is higher than the low frequency band within 3 hours after the earthquake before the earthquake,and the mid-high frequency band in the quiet period is lower than the mid-to-high frequency range within 3 hours after the earthquake before the earthquake provides a new reference for the study of disturbance before and after the earthquake.(2)The paper has systematically sorted out the process of identifying typhoon disturbance signal in superconducting gravity observation data,combine with typhoon data and the typhoon's time-frequency domain characteristics of gravity disturbance signals,and established typhoon parameters(typhoon intensity,typhoon center)through time-domain and frequency-domain analysis The minimum air pressure,the distance between the center of the typhoon and the station,etc.)and the power spectrum density of the characteristic frequency band of the disturbance signal(PSDF)in the gravity data,to obtain the understanding of the magnitude of the typhoon's influence on the gravity data and the characteristic frequency of the disturbance signal.It is found that the influence of the typhoon on the gravity data decreases with the increase of the distance between the typhoon center and the station,and increases with the increase of the typhoon intensity,and the correlation with the lowest air pressure at the typhoon center is weak.Gravity observation data responds greatly to typhoons in the range of 100 °-165 ° inverse azimuth and distances of 1500 km-3000 km.The influence within the range decreases dynamically with the increase of distance,and the peak PSDF is 20.4 d B.In the area where the distance between the typhoon center and the station is greater than 3000 km,the typhoon has less interference to the gravity data,the PSDF value is attenuated below 17 d B,and the impact range is similar.The interference to gravity data when the distance between the typhoon center and the station is less than 1500 km is greater than the interference to gravity data when the distance between the typhoon center and the station is greater than 3000 km.(3)Quantitatively analyze the characteristics of the infragravity wave response signal in the same frequency band in the superconducting gravity data and its correlation with the change of the infragravity wave height,and obtain the understanding of the magnitude and time-varying characteristics of the gravity data disturbance signal by the infragravity wave.It was found that the data of the 0-0.0325 Hz superconducting gravimeter with a sampling interval of 3 hours and the infragravity wave high correlation coefficient calculated from the seafloor pressure data of the 21415 station of the DART system is-0.992,which is obviously negatively correlated.The perturbation signal of the infragravity wave to the superconducting gravity measurement data presents a diurnal variation of two peaks and troughs.The amplitude of the daily variation exceeds 1 ?Gal when the amplitude is large,and it is about 0.5 ?Gal when the amplitude is small.The annual variation trend of the perturbation signal of the infragravity wave to the superconducting gravity measurement data is low in summer and high in winter,which is consistent with the high annual variation of the infragravity wave.The 5-month variation range is 4.41 ?Gal. |
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