Optimization And Application Of Geomagnetic Data Processing Method On Deep Sea

As the object of data processing and the original data of marine geomagnetic data analysis and utilization,the data quality is the basis to ensure the accuracy of marine geomagnetic data.For marine geomagnetic data processing methods,the quality of geomagnetic diurnal variation correction is the key to the accuracy of marine geomagnetic data.Geomagnetic anomaly poling can eliminate the phenomenon that the distribution and center position of geomagnetic anomaly isoline caused by the magnetization of geomagnetic field are not consistent with the actual position of underground magnetic body,but in the low latitude area,the processing is more complex,which will lead to the geomagnetic anomaly isoline stretching along the vertical direction of geomagnetic declination and strip interference.In this paper,through the analysis of the original marine geomagnetic data,the jump value judgment method is established.The interpolation method suitable for different data types is studied.The data of international geomagnetic diurnal variation stations are collected.The components of geomagnetic diurnal variation data are analyzed from frequency domain and wavelet domain.The optimization method of geomagnetic diurnal variation correction is also studied.On the basis of summing up the conventional poling and methods in frequency domain,this paper analyzes the difficulties and reasons existing poling operation in the low latitude area.Combined with the ideas and advantages of the existing poling methods in the low latitude area,the poling factor is modified and compared in the model forward data.On the basis of the above research,the optimization method of marine geomagnetic data processing is applied to the measured geomagnetic data in deep sea area near the equator.The geomagnetic anomaly data is obtained.The accuracy evaluation and error comparison with the processing results of conventional methods are carried out.The geomagnetic anomaly data are poled on low latitude,extended upward and inversed.The distribution characteristics of geomagnetic anomaly and the preliminary understanding of structure are obtained.The results show that:(1)When preprocessing the geomagnetic raw data,the linear interpolation method should be used to supplement the missing data segment;and the cubic spline function interpolation method should be used to interpolate and encrypt the data collected by the submarine diurnal variation station;for the data collected by the geomagnetic instrument,the missing data should be analyzed first,the interpolation method is selected: linear interpolation is used to supplement the missing data segments with monotonicity,and piecewise cubic Hermite interpolation is used to supplement the missing data segments without monotonicity.(2)For the geomagnetic diurnal variation data,the regular change with period more than 5 h is the effective value of geomagnetic diurnal variation correction;Sym8 wavelet is selected as the wavelet basis function,and the geomagnetic diurnal variation correction can be obtained by 7-layer discrete wavelet decomposition and single reconstruction of geomagnetic diurnal variation data,which is better than low-pass filtering.(3)The strip interference along the vertical direction of geomagnetic declination and the stretching of geomagnetic anomaly isoline in the results of reduction to the pole in the low latitude area are mainly determined by the amplitude of reduction to the pole factor and the noise in geomagnetic anomaly data,which is independent of the phase spectrum of reduction to the pole factor.The exponential pseudo dip reduction to the pole method proposed in this paper has obvious advantages in the application of model forward test and measured geomagnetic data,and can effectively improve the existing reduction to the pole method effect in the low latitude area.(4)The distribution of geomagnetic anomalies in deep sea area near the equator is generally divided into east and west parts.In the west part,almost all of them are positive anomalies with small geomagnetic gradient,simple geological structure and small overall buried depth.In the north and south part,the magnetic anomalies are complex and large buried depth.In the east part,the positive anomalies are dominant,the geomagnetic anomalies change greatly,and the underground magnetic bodies between the north and the south are discontinuous more obvious fault structure.